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Technology and the Treatment of Children with Autism Spectrum Disorder Cardon
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Foreword
I have had the great fortune to meet many children and adults on the autism spectrum and their family members throughout my career. They have taught me a great deal about what it means to live with autism and about the role professionals have played in their lives. I have learned that, for many families, interacting with professionals can help or hinder, decrease or increase stress, empower or disempower, cause or resolve conflict, create or solve problems.
From a professional perspective, we would do well to be guided by the work of Carl Dunst, the Turnbulls and others who have advocated for decades that family empowerment should be a primary outcome of intervention. Over the past two decades, we have amassed a large body of research supporting the use by professionals of family-centred practices that empower families. The use of a familycentred approach has been linked to improved parenting self-efficacy, parenting skills, reduced parenting stress, participation in community activities, knowledge of child development, family quality of life, access to support systems and selfadvocacy. Resources are available to help professionals to learn about and adopt a family-centred approach and to assess how effective they are in implementing family-centred practices.
From the parent’s perspective, there has been little available information until now to guide their interactions with professionals, who will undoubtedly vary in their knowledge and use of family-centred practices. This excellent book helps to address this gap. It is the first publication of its kind to provide parents with a framework to guide their interactions with professionals and educators in order to create effective education plans and programmes for their child on the autism spectrum.
Empowering Parents of Children with Autism Spectrum Disorder is focused on supporting parents of school-aged children to have meaningful input into their child’s educational planning and programming. As pointed out by the authors, parents often report being confused by conflicting information regarding which services and programmes can best meet their child’s needs. They can feel frustrated and marginalised by professionals. The Cycle of Learning framework is introduced in this book as a means to assist parents in their decision-making, to identify a future vision for their child, determine key barriers and set learning priorities. The book
uses case studies to highlight how parents can implement the framework. These case studies ensure that the book remains very practical and accessible. While providing parents with practical strategies within a guiding framework to support their child’s education, the book will also be of benefit to professionals— particularly educators. The Cycle of Learning framework is underpinned by principles of empowerment and family-centred practices, facilitating positive and productive partnerships between professionals and parents. It is through such partnerships that children with autism spectrum disorder (ASD) and their families can realise their visions.
Keen Griffith University, Brisbane, Australia
Autism Centre of Excellence
Deb
Acknowledgements
The authors wish to acknowledge the tremendous contribution of Natalie Bird, Lorna Parker, Christine Bergmann, Bernadette Beasley, Todd Whitehead, Lisa (Callum’s mother) and Nicole (Ann’s mother) who gave their time and shared their stories that made this book possible. These parents demonstrate every day the strength and impact that parents can have when they become empowered to make their voice and the voices of their children heard. Without these individuals and the countless other parents who advocate for their children and support their children to advocate for themselves, this book would not have been possible.
Part III
Part I
Parents,
Effective Practice, and Critical
Decision-Making: What do we know
Chapter 1 Effective Practice and Decision-Making for Parents of Children with Autism Spectrum Disorder
Abstract This chapter provides an introduction to the first section of the book in which research and current knowledge is presented about: the challenges faced by parents of children with autism spectrum disorder; the practices that have been found to have an evidence-base for children with autism spectrum disorder, and the Cycle of Learning decision-making framework.
Parents are experts when it comes to their children and play a critical role in teaching and guiding their children’s learning as they grow from early childhood into adulthood. For parents of children with autism spectrum disorder (ASD), this responsibility often starts as soon as their child is diagnosed, with more complex challenges arising as their children mature. As a result, parents are required to take on a variety of roles as they make decisions about their child’s learning and advocate for their child in different settings (Stoner & Angell, 2006). Unfortunately, parents of children with ASD often face obstacles as they seek to give their child the educational opportunities that will enable them to develop their skills and achieve a high quality of life. In addition to learning about ASD and what this means for their child, parents also have to navigate a complex system of government policies, societal attitudes, educational programs, and conflicting information from health providers, educators, and other parents (Foster, Rude, & Grannan, 2012). Moreover, once their child enters school, parents often take a back seat to educators who traditionally take the lead in developing education plans and programs for their children (Fish, 2006). ASD is a pervasive neurodevelopmental disorder, marked by impairments in social communication and restricted and repetitive behaviours, as well as differences in sensory and information processing (American Psychiatric Association, 2013). Individuals with ASD are unique, with the characteristics associated with ASD presenting in varying ways and creating different challenges for each person (Zeman, Swanke, & Doktor, 2011). The number of children diagnosed with ASD has increased significantly over the past 20 years (Matson & Kozlowski, 2011). At the same time the inclusion of students with disabilities in mainstream education settings has become the prevailing model (Renzaglia, Karvonen, Drasgow, & Stoxen, 2003). As a result, the majority of students with ASD are currently being educated in mainstream education settings. This has had a significant impact not just on the education system, but also on teachers and parents working to support these students in meaningful ways. Consequently, primary and secondary school
A. Webster et al., Empowering Parents of Children with Autism Spectrum Disorder, DOI 10.1007/978-981-10-2084-1_1
3
educators are being asked to cater for the needs of children with ASD in environments that present a myriad of potential stressors for these children, including, but not limited to, demands for social interaction, sensory overload, and limited levels of structure (Hull Learning Services, 2004; Whitaker, 2007).
Legislation in different countries (Rotatori, Bakken, Burkhardt, Obiakor, & Sharma, 2014) mandates that schools have a duty to include and provide supports to students with disabilities, including those with ASD, providing fair and equal opportunities to access a high quality education that allows students to reach maximum achievement on academic standards and assessments (Dempsey, 2012; Foster et al., 2012; U.S. Department of Education, 2015). Parents have been recognised as essential team members in the educational planning and decision-making process for children with ASD. Parental involvement has been consistently linked to outcomes for children with ASD, including increased social emotional learning and behaviour (Iovannone, Dunlap, Huber, & Kincaid, 2003), self-determination (Field & Hoffman, 1999), and generalisation and maintenance of skills (Lynch & Irvine, 2009). In reality, however, home-school collaboration is often more an ideal than a reality as parents struggle to be actively involved in creating education plans and programs that will enable their child to achieve meaningful goals and realise their dreams.
Parents of children with ASD are reporting high levels of stress and frustration in accessing appropriate support that will enable their children to become independent and self-determined adults (Hayes & Watson, 2013). In addition, with the increased information available in the media and on the internet (Mackintosh, Myers, & GoinKochel, 2005; Parsons, Lewis, & Ellins, 2009), parents of children with ASD are constantly being confronted with an overwhelming number of reports on programs and interventions claiming to help individuals with ASD or, in some cases, cure them. As a result, many parents are spending excess time and money on strategies which have been found to be ineffective and even harmful (Carlon, Stephenson, & Carter, 2014), rather than on those that have been found to consistently result in beneficial outcomes for children with ASD. At the same time, parents are stating (Tucker & Schwartz, 2013) that they often feel disengaged from school planning processes, which are often dominated by educators (Fish, 2006), and are made to feel marginalised (Oprea & Stan, 2012) by education professionals who do not view them as knowledgeable contributors to their child’s education program (Keenan, Dillenburger, Doherty, Byrne, & Gallagher, 2010).
Parents have unique knowledge of their children’s needs, strengths, interests, and current and future goals, and are their child’s first teacher, supporter, advocate, and voice to the outside world. As their child grows, it is critical that parents collaborate with educators to share knowledge about their child, set key priorities and goals, determine appropriate strategies and supports, and evaluate achievement (National Research Council, 2001; Ruble & McGrew, 2015). As the most stable and influential people in a child’s life (Dunlap, 1999), parents are in a unique position to ensure that education plans and programs are designed to meet their child’s unique way of learning and interacting with the world, while reflecting their family’s culture, language, values, and spirituality, and striving towards educational achievement, attainment of personal goals, and a better quality of life and optimal outcomes for both
Fig. 1.1 Cycle of learning framework
the child and their family (Harte, 2009; Osher & Osher, 2002; Whitaker, 2007; Zeman et al., 2011).
The primary purpose of this book is to present research and case studies illustrating how parents of children with ASD have become empowered through the use of the Cycle of Learning (CoL) framework (see Fig. 1.1) to lead educational decisionmaking and planning for their child. This research-based framework has enabled parents to work with educators and service professionals to establish an overall vision for their child and to select, implement, and evaluate the most effective programs that will allow their children to realise their dreams and achieve meaningful life goals. In addition, parents have increased their self-efficacy to successfully advocate for effective school, community, and home-based education programs for their child with ASD.
The book is divided into three sections. In the initial section of the book, the first chapter will provide an overview of the research on current issues faced by parents of children with ASD. This will be followed by a review of the research on evidence-based practices for students with ASD in inclusive school settings. In the last chapter in this section, the CoL framework will be discussed and the research underpinning its individual components will be presented. In the second section, case studies will be presented to illustrate how parents have utilised the CoL framework in their collaboration with educators to develop and implement education plans for their children. Finally, the last section will present case studies examining the use of the CoL by parents as they advocate for more systematic change in education programs and policies for children with ASD. This book is intended as an academic text aimed at parents, professionals, and researchers working with individuals with ASD and their families. It should be noted that while the parent contributors to this book have become further educated about ASD through university study, the framework, strategies, and ideas presented throughout the book are intended to be practical and useful for all.
References
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Washington, DC: American Psychiatric Publishing. Retrieved from http://www.terapiacognitiva.eu/dwl/dsm5/DSM-5.pdf
Carlon, S., Stephenson, J., & Carter, M. (2014). Parent reports of treatments and interventions used with children with autism spectrum disorders (ASD): A review of the literature. Australasian Journal of Special Education, 38, 63–90. doi:10.1017/jse.2014.4
Dempsey, I. (2012). The use of individual education programs for children in Australian schools. Australasian Journal of Special Education, 36, 21–31. doi:10.1017/jse.2012.5
Dunlap, G. (1999). Consensus, engagement, and family involvement for young children with autism. Research and Practice for Persons with Severe Disabilities, 24, 222–225.
Field, S., & Hoffman, A. (1999). The importance of family involvement for promoting selfdetermination in adolescents with autism and other developmental disabilities. Focus on Autism and Other Developmental Disabilities, 14, 36–41. doi:10.1177/108835769901400105
Fish, W. W. (2006). Perceptions of parents of students with autism towards the IEP meeting: A case study of one family support group chapter. Education and Treatment of Children, 127, 56–68.
Foster, A., Rude, D., & Grannan, C. (2012). Preparing parents to advocate for a child with autism. The Phi Delta Kappan, 94, 16–20.
Harte, H. A. (2009). What teachers can learn from mothers of children with autism. Teaching Exceptional Children, 42, 24–30.
Hayes, S. A., & Watson, S. L. (2013). The impact of parenting stress: A meta-analysis of studies comparing the experience of parenting stress in parents of children with and without autism spectrum disorder. Journal of Autism and Developmental Disorders, 43, 629–642. doi:10.1007/ s10803-012-1604-y.
Hull Learning Services. (2004). Supporting children with autistic spectrum disorder. London: David Fulton.
Iovannone, R., Dunlap, G., Huber, J., & Kincaid, D. (2003). Effective educational practices for students with autism spectrum disorders. Focus on Autism and Other Developmental Disabilities, 18, 150–165.
Keenan, M., Dillenburger, K., Doherty, A., Byrne, A., & Gallagher, S. (2010). The experiences of parents during diagnosis and forward planning for children with autism spectrum disorder. Journal of Applied Research in Intellectual Disabilities, 23, 390–397. doi:10.1111/j.1468-3148.2010.00555.x.
Lynch, S. L., & Irvine, A. N. (2009). Inclusive education and best practice for children wtih autism spectrum disorder: An integrated approach. International Journal of Inclusive Education, 13, 845–859. doi:10.1080/13603110802475518.
Mackintosh, V. H., Myers, B. J., & Goin-Kochel, R. P. (2005). Sources of information and support used by parents of children with autism spectrum disorders. Journal of Developmental Disabilities, 12, 41–51.
Matson, J. L., & Kozlowski, A. M. (2011). The increasing prevalence of autism spectrum disorders. Research in Autism Spectrum Disorders, 5, 418–425. doi:10.1016/j.rasd.2010.06.004. National Research Council. (2001). Educating children with autism. Washington, DC: National Academy Press.
Oprea, C., & Stan, A. (2012). Mothers of autistic children. How do they feel? Procedia – Social and Behavioral Sciences, 46, 4191–4194. doi:10.1016/j.sbspro.2012.06.224.
Osher, T. W., & Osher, D. M. (2002). The paradigm shift to true collaboration with families. Journal of Child and Family Studies, 11, 47–60. doi:10.1023/A:1014715527823.
Parsons, S., Lewis, A., & Ellins, J. (2009). The views and experiences of parents of children with austistic spectrum disorder about educational provision: Comparisons with parents of children with other disabilities from an online survey. European Journal of Special Needs Education, 24, 37–58. doi:10.1080/08856250802596790
References
Renzaglia, A., Karvonen, M., Drasgow, E., & Stoxen, C. C. (2003). Promoting a lifetime of inclusion. Focus on Autism and Other Developmental Disabilities, 18, 140–149. doi:10.1177/10883 576030180030201
Rotatori, A. F., Bakken, J. P., Burkhardt, S. A., Obiakor, F. E., & Sharma, U. (2014). Special education international perspectives: Biopsychosocial, cultural, and disability aspects (Vol. 27). Bingley, UK: Emerald Group.
Ruble, L., & McGrew, J. H. (2015). COMPASS and implementation science. New York: Springer. Stoner, J. B., & Angell, M. E. (2006). Parent perspectives on role engagement: An investigation of parents of children with ASD and their self-reported roles with education professionals. Focus on Autism and Other Developmental Disabilities, 21, 177–189.
Tucker, V., & Schwartz, I. (2013). Parents’ perspectives of collaboration with school professionals: Barriers and facilitators to successful partnerships in planning for students with ASD. School Mental Health, 5, 3–14. doi:10.1007/s12310-012-9102-0
U.S. Department of Education. (2015). Building the legacy: IDEA 2004. Retrieved from http:// idea.ed.gov/explore/home
Whitaker, P. (2007). Provision for youngsters with autistic spectrum disorders in mainstream schools: What parents say and what parents want. British Journal of Special Education, 34, 170–178. doi:10.1111/j.1467-8578.2007.00473.x
Zeman, L. D., Swanke, J., & Doktor, J. (2011). Measurable successes for children with ASD: Perspectives from mothers’ virtual journals. School Social Work Journal, 36, 61–78.
Chapter 2 Defining the Problem
Abstract This chapter presents international research on experiences and challenges reported by parents of children with autism spectrum disorder (ASD), in making informed choices and engaging with professionals regarding therapeutic and education programs that will allow their children to achieve success throughout their lifespan. Parents of children with ASD are currently confronted with an array of confusing and conflicting information about the services and programs that will best help their children. As a result, many parents feel frustrated and overwhelmed as they go about making decisions for their children, and have become disempowered in decision-making processes, particularly once their child begins school. This chapter will overview the current research on issues faced by parents of children with ASD, and will briefly examine the characteristics and implications of ASD for children with and families. The impact of the child’s diagnosis and resulting stress on parents and families will be explored, followed by an examination of the particular challenges faced by parents once their children commences school. Finally, a recent study will be reviewed, which explored the satisfaction, confidence and training needs of parents of school-aged children with ASD.
A. Webster et al., Empowering Parents of Children with Autism Spectrum Disorder, DOI 10.1007/978-981-10-2084-1_2
2 Defi ning the Problem
The diagnosis of a child with autism spectrum disorder (ASD) is a time of tremendous uncertainty, change, and stress for parents and families. Parents are quickly faced with navigating a maze of information and bureaucratic processes as they attempt to find the best programs to support their child. Although family involvement is considered essential in programs for children with ASD, many parents report that they are increasingly being marginalised in planning processes, and are feeling frustrated with inconsistent and ineffective practices for their children. It is therefore critical that parents be provided with information and support to move into a more empowered and directive role to plan for their child, and to access the interventions and programs that will enable their child to reach their goals and dreams. For many parents, the first step is to learn what a diagnosis of autism spectrum disorder (ASD) means for their child and their family.
2.1 Introduction: Children with Autism Spectrum Disorder
There is a saying in the autism community “If you’ve met one person with autism –you’ve met ONE person with autism” - Dr. Stephen Shore. Although all individuals with autism spectrum disorder (ASD) share similarities in the core areas of impairment (i.e., social communication and restricted and repetitive behaviours and interests) associated with ASD (McAfee, 2002; Murray-Slutsky & Paris, 2000), they may demonstrate a wide range of behaviours and skills in each of these areas (Attwood, 2014). In the 1970s Lorna Wing was one of the first autism researchers to identify the “spectrum” of skills demonstrated by individuals with autism (Wolff, 2004). From Wing’s early classification of autism as a triad of impairment (Wing & Gould, 1978), the recent reclassification of autism has also seen a change in criteria to a dyad of core deficits in social communication and restricted and repetitive behaviours and interests (Attwood, 2014). Autism is no longer categorised as a group of related disorders, but as one disorder with a spectrum of characteristics (American Psychiatric Association, 2013). A diagnosis of autism will also now include an indication of the level of impairment in social communication and restricted and repetitive behaviours (Vivanti et al., 2013), reflecting the support needs of the individual in each area. This change represents a significant shift from the perception of ASD as a core set of behaviours, to a new understanding that individuals with ASD exhibit a spectrum of abilities and needs in the two diagnostic criteria areas.
In addition to the core characteristics cited in the diagnostic criteria for ASD, researchers (e.g. Freeth, Ropar, Mitchell, Chapman, & Loher, 2011; Grossman & Tager-Flusberg, 2012) have identified key differences in the way that many individuals with ASD process information. These researchers (Baron-Cohen, 1995; Happé & Frith, 2006; Minshew & Williams, 2008) argue that not only do individuals with ASD frequently exhibit differences in cognitive processing, but that these cognitive differences may actually underpin the core deficits in social communication and restricted and repetitive behaviours and interests associated with ASD. The
research in this area has primarily explored three specific theories regarding differences in cognitive processing exhibited by individuals with ASD (Rajendran & Mitchell, 2007). These theories include differences and impairments in theory of mind, executive functioning, and central coherence (Attwood, 2014). Theory of mind is also referred to as “mind blindness” (Baron-Cohen, 1995) and involves the ability to understand that other people have thoughts and feelings that are different from one’s own. People who have difficulty in theory of mind experience problems with making sense of the intentions and behaviour of others and predicting what they will do next (Attwood, 2014). Weak central coherence refers to the difficulty that many people with ASD have in understanding or seeing the overall picture (Happé & Frith, 2006). Although this has been cited as an area of difficulty, both parents and individuals with ASD have argued that the ability to focus on small details is also an area of strength. Executive functioning is another commonly cited area of cognitive difficulty for individuals with ASD (Rajendran & Mitchell, 2007), defined as the ability to engage in a sequence of problem-solving steps in order to attain a future goal. Executive functioning encompasses behaviours such as planning, impulse control, and inhibition and skills in organisation, working memory, and flexible thinking. Although difficulties in executive function, theory of mind, and central coherence are not unique to individuals with ASD, have been demonstrated to have a significant impact on the way that children with ASD engage with learning or social environments (Dodd, 2004).
Similarly, Vermeulen (2001) emphasises that individuals with autism think in much more linear ways than their neurotypical peers, demonstrating less cognitive flexibility in different contexts. He contends that rather than demonstrating a lack of skills, individuals with ASD experience “context blindness” in which they are unable to use context to create meaning (Vermeulen, 2015). Similarly, researchers with ASD, such as Temple Grandin (Grandin, 2013) and Wenn Lawson (Lawson, 2011), assert that for them, autism is characterised primarily as a difference in how they think or view their world. Research confirms that many individuals with ASD see information processing differences as their primary impairment, which then leads to secondary deficits in social communication and restricted and repetitive behaviours (Chamak, Bonniau, Jaunay, & Cohen, 2008). Parents also report that differences in thinking are a key characteristic of their children with ASD, but are often misunderstood by educators and other professionals who primarily focus on the child’s behaviour difficulties (Sciutto, Richwine, Mentrikoski, & Niedzwiecki, 2012; Stanton, 2000). Moreover, parents suggest that teachers view these behaviours as a choice, indicative of a naughty child or poor parenting, and fail to understand that they may be the manifestation of perceptual and processing differences characteristic of children with ASD. Parents also stress that their children cannot be categorised by a diagnosis or specific set of criteria, as individuals with ASD are widely diverse, each having their own unique strengths, interests, and needs.
The strengths of individuals with ASD have not received the same attention in research as areas of difficulty, but a number of researchers have begun to explore the unique skills demonstrated by children and adults with ASD. Researchers have
2 Defi ning the Problem
particularly focused on determining the prevalence and type of savant skills in this population (Howlin, Goode, Hutton, & Rutter, 2009; Treffert, 2014). Some researchers (Quirici, 2015; Sciutto et al., 2012), however, argue that it is a common misconception that all individuals with ASD have savant skills. No matter whether an individual is considered to have savant abilities or not, researchers (e.g. Frith, 1997; Joseph, Tager-Flusberg, & Lord, 2002) agree that most individuals with ASD have an uneven profile of abilities with at least some skills that are out of sync with their overall level of ability. For example, a person with ASD may have general difficulties with reading, but be very good at mathematical calculations. In addition, this disparity does not just exist between different knowledge areas, but can exist within the same academic or skill area in school or work settings. An example of this would be a child with ASD who can decode and spell words, but has difficulty with reading comprehension. Similarly some individuals might be above average in mathematical calculations but very poor at measurement of time and money.
This disparity of knowledge and skills can create even more misunderstandings for individuals with ASD. They are often assumed to be noncompliant or disruptive because they are not able to demonstrate a skill in an area that is seemingly similar to another skill in which they have previously excelled. In addition, some individuals with ASD have quite significant intellectual and language impairments (Volkmar, Lord, Bailey, Schultz, & Klin, 2004). Ascertaining the specific profile of skills and needs of individuals with ASD starts with the initial diagnosis, but becomes particularly critical as parents begin to access services and education programs. This also marks a time of increased stress for parents as they begin the process of negotiating with schools and service providers for effective programs that meet their child’s specific needs (Parsons, Lewis, & Ellins, 2009).
2.2 Challenges Reported by Parents
2.2.1 Impact of ASD: Stress Levels
A number of studies suggest that raising a child with ASD is enormously stressful and challenging for families (Baker-Erickzen, Brookman-Frazee, & Stahmer, 2005; Falk, Norris, & Quinn, 2014; Myers, Mackintosh, & Goin-Kochel, 2009; Phetrasuwan & Shandor Miles, 2009; Pozo & Sarriá, 2014). Researchers have found that parents of children with ASD experience higher levels of stress compared to both parents of typically developing children and parents of children with other disabilities, such as intellectual disabilities (Abbeduto et al., 2004; Baker-Erickzen et al., 2005; Weiss, 2002) or cerebral palsy (Hayes & Watson, 2013). Parents describe experiencing initial feelings of surprise, sadness, shock, and rejection following their child’s diagnosis (Martins, Bonito, Andrade, Albuquerque, & Chaves, 2015). The impact of the initial diagnosis on families, however, has been found to
vary depending on their prior knowledge about ASD and their support structures (Myers et al., 2009; Stuart & McGrew, 2009).
Following their child’s diagnosis, parents are faced with a range of extra pressures as they attempt to learn about ASD and what this means for their child. Financial strains and time pressures may lead to decreased self-efficacy and increased physical and mental health difficulties for families (Karst & Van Hecke, 2012). Other studies have found that families of children with ASD experience an overall decreased quality of life (Meadan, Halle, & Ebata, 2010; Tincani, Cucchiarra, Thurman, Snyder, & McCarthy, 2014) as a result of dealing with their children’s challenging behaviours. Parents also report facing hidden social costs as they decrease their engagement in social activities due to concerns for their child (Schaff, Toth-Cohen, Johnson, Outenn, & Benevides, 2011). Ewles, Clifford, and Minnes (2014) suggest that the ongoing financial, emotional, and physical responsibilities placed on parents of children with ASD put a significant strain on their psychological well-being (Myers et al., 2009). This is exacerbated by the need to continually advocate for services for their child. Parents confirm that much of their stress and exhaustion is caused by the continued necessity of having to fight for services, cope with complicated policies or negative societal attitudes, and constantly having to communicate and build relationships with education and health professionals (BlueBanning, Summers, Frankland, Nelson, & Beegle, 2004).
Parents of children with comorbid disabilities or with needs on the severe end of the autism spectrum, generally experience higher levels of stress and increased caregiver duties than do other parents of children with ASD (Zablotsky, Boswell, & Smith, 2012). Studies (Benson, Karlof, & Siperstein, 2008; Zablotsky et al., 2012) have also found that their child’s level of need is linked to involvement and satisfaction of parents with their child’s school, with parents of children with higher needs having the lowest level of involvement and satisfaction. Parents may feel blamed or judged by professionals or community members for their child’s deficits and behaviours (Starr & Foy, 2012), making them even less likely to develop the trusting or collaborative partnerships needed to reach optimal outcomes for their child with ASD (Stoner et al., 2005).
ASD impacts family dynamics as well as parents’ relationships. Divorce rates are higher for families of children with ASD (Hartley et al., 2010), with additional stress placed on families of children with particularly challenging behaviours (Rao & Beidel, 2009). Stress on siblings has also been examined, with some studies finding positive effects such as increased self-concept for siblings (Mates, 1990), whereas others have identified higher levels of loneliness and behaviour difficulties for siblings of children with ASD (Bågenholm & Gillberg, 1991). Mothers of children with ASD have been noted to experience more stress and levels of anxiety than fathers (Phetrasuwan & Shandor Miles, 2009; Pozo & Sarriá, 2014), perhaps because of the greater amount of time they generally spend with the child during their early years. Additionally, researchers have suggested that families have less time for family activities (Karst & Van Hecke, 2012), and parents often experience physical and emotional exhaustion as they struggle to cope with their child’s poor sleeping and eating patterns (Stoner et al., 2005).
2 Defi ning the Problem
Accessing appropriate services and supports to help both their child and their family is another source of stress for parents. With the recent emphasis on early intervention services, parents of children with ASD are experiencing heightened levels of anxiety about choosing the right programs, or inabilities to access particular programs due to geography or lack of funds (Mackintosh, Goin-Kochel, & Myers, 2012). Parents also indicate that lack of support to help them access or make decisions about appropriate services (Stephenson, Carter, & Kemp, 2012) is a frequent source of frustration and anxiety. Mothers who are experiencing stress and anxiety may experience decreased self-esteem and a reluctance to engage with supportive services (Keen, Couzens, Muspratt, & Rodger, 2010). Other parents may focus on problem solving or positive aspects of their situation as a means of coping (Hastings et al., 2005), or may manage stress by networking with peers in early intervention programs and support groups (Boyd, 2002). Keen et al. (2010) also suggests that professional support is critical to alleviating the stress of parents as they access early intervention services following their child’s diagnosis. In contrast, lack of communication and support from school leaders and teachers has been cited as a key cause of stress and dissatisfaction for parents of school-aged children with ASD (Starr & Foy, 2012; Tucker & Schwartz, 2013).
2.2.2 Engaging with Education Programs
Once their child enters school, parents must learn to navigate a whole new system of policies and practices. Lilley (2012) examined the experiences of 22 mothers as they enrolled their children with ASD in school for the first time, and concluded that a common thread in all of the mothers’ narratives was the experience of stigmatisation both for their child and for themselves. In another study (Stoner et al., 2005), parents of children with ASD reported the change from early intervention to schoolbased programs was particularly difficult. They experienced high levels of confusion when attending their first education planning sessions at the school, feeling they had to fight to obtain supports for their child, which they still felt were inadequate to meet their child’s needs. This led to a breakdown in trust with the school and school staff.
Collaborative partnerships between parents and educators are considered best practice, with the importance of including parents as full team members clearly documented in research and policy. (National Research Council, 2001; US Department of Education, 2015; Zablotsky et al., 2012). Often these partnerships are falling short of recommended practice, however, impacting on the achievement of optimal outcomes for children with ASD in school environments. There is much research on the multiple barriers affecting the establishment and maintenance of effective, collaborative parent-educator partnerships (White, 2014). These include poor communication; confidence and perceptions of educators; confidence and perceptions of parents; parental constraints including stress and time; conflict between parents and educators; insufficient school-based services; educators having a lack of
specific ASD knowledge and training; and a myriad of issues relating to decisionmaking processes and educational planning. Other factors affecting levels of parental involvement in their child’s education include socio-economic standing, financial pressures, marital status, cultural beliefs, occupational rank, language barriers, a lack of parental confidence in the school system, poor communication practices between parents and educators, inadequate understanding of the impacts of ASD by educators, the number of children parents are caring for, and the level of disability of the child with ASD (Ryan & Runswick-Cole, 2009; Tincani et al., 2014; Todd, Beamer, & Goodreau, 2014).
Current legislation and policies across the world emphasise the importance of collaborative, positive partnerships between parents and educators, as a core element in shaping the educational experiences of children with autism (National Research Council, 2001; US Department of Education, 2015; Zablotsky et al., 2012). Parents have been recognised as essential team members, with their involvement in educational decision making and planning for their child consistently linked to students’ cognitive development, academic achievement, attitudes, and aspirations (Brand, 1996; Foster, Rude, & Grannan, 2012; Osher & Osher, 2002; Turnbull & Turnbull, 1990; US Department of Education, 2015). Despite this acknowledgement of the important role parents play in their child’s education, research (Spann, Kohler, & Soenksen, 2003; Tucker & Schwartz, 2013) suggests that educators continue to struggle to include parents or individuals with ASD in education planning and decision-making processes, and that, education plans and programs often fail to include the concerns, priorities, or values of parents (Ruble, McGrew, Dalrymple, & Jung, 2010). As a result, legal disputes regarding education programs and provisions for students with ASD have increased rapidly over the past 15 years (Turnbull, Wilcox, & Stowe, 2002; White, 2014). In a recent review of 97 complaints filed in the United States, White (2014) found that these disputes focused on parent’s dissatisfaction with the identification of their children’s needs, implementation of appropriate programs to meet those needs, inclusion of parents in the education planning process, inadequate evaluation of their child’s learning and outcomes, and concerns about staff qualifications, and behaviour and disciplinary procedures. In Australia, Dempsey (2003) found that there was limited evidence that disability discrimination legislation had led to improved enrolment practices for students with disability, with students with ASD and other disabilities continuing to be excluded from education programs on a regular basis.
In contrast to early intervention programs which are often family centred (Stoner et al., 2005), parents often report being dismissed by school personnel as valuable contributors in assessing their child’s needs, providing information about their child, setting goals, and planning for their child (Ferrel, 2012; Stoner, Angell, House, & Bock, 2007; Tucker & Schwartz, 2013). In another study, mothers of children with ASD reported they were silenced by educators by either not being given a voice or by not being listened to when they did speak (Carpenter & Austin, 2007). These mothers also felt judged by educators, reporting they were told what to do for their child rather than being included in discussions or asked to provide ideas about how to help their child. This research demonstrates a disturbing trend. Without parents as key participants in planning processes, opportunities are limited
2 Defi ning the Problem
for children with ASD to achieve goals, which are meaningful for both the child and their family. More importantly, parents may have differing ideas and values from educators, but lack the confidence to voice them, resulting in education programs that focus on outcomes that are not supported at home (Osher & Osher, 2002; Todd et al., 2014).
When communication and collaboration between parents and schools break down, tensions can quickly escalate into conflict. Lake and Billingsley (2000) found that nearly 90 % of parents reported that conflict with schools occurred due to schools and parents having differing perceptions of children’s needs. Parents revealed dissatisfaction with school teams who did not recognise their child’s individuality (individual strengths and limitations), and felt schools often operated from a deficit perspective, placing too much emphasis on what their children could not do as opposed to focusing on their strengths. Parents also report tensions arise when schools fail to meet legislative or policy requirements that they plan and provide strategies and support so that students are able to participate and achieve in education programs (Lilley, 2015; White, 2014). Lack of planning and support for children during transitions has been particularly highlighted as an area of concern (Lilley, 2015; Parsons et al., 2009). Parents also indicate they experience conflict with school leaders and teachers about what education programs and supports are reasonable and appropriate for their child in the school environment, and highlight a need for improved mediation processes to avoid the need for legal action to ensure their child is provided with the entitled supports (Tincani et al., 2014).
Parents frequently cite the limited level of knowledge of ASD and evidencebased strategies exhibited by teachers and school leaders as a source of concern and dissatisfaction with their child’s education programs (Starr & Foy, 2012; Tincani et al., 2014; Whitaker, 2007). Starr and Foy found that parents felt most of their child’s teachers lacked training or knowledge about ASD. Almost half of the parents expressed the need for school personnel to have more disability-specific knowledge in order to understand their children’s needs, and felt they needed information and training on effective intervention techniques. Parents also report high rates of dissatisfaction with the level and quality of autism-specific support provided by schools for their child (Renty & Roeyers, 2006). These parents stress that educators often fail to provide programs which address the core characteristics of ASD, such as deficits in social communication and restricted and repetitive behaviours (Tincani et al., 2014; Tucker & Schwartz, 2013), and are unable to appropriately address their children’s behaviour difficulties or even recognise that the cause of these behaviours might be linked to the characteristics of ASD (Whitaker, 2007).
By contrast, communication between parents and schools is often cited as a pivotal element in parents’ satisfaction. Researchers suggest that good communication can help parents and educators to develop trust and collaborative relationships (Angell, Stoner, & Shelden, 2009; Renty & Roeyers, 2006), whereas poor or insufficient communication with educators is one of the most commonly mentioned sources of parent frustration and dissatisfaction (Whitaker, 2007; Zablotsky et al., 2012). Parents cite many issues with communication with schools, including fre-
quency of communication, general lack of communication, lack of follow up, misunderstood communications, dishonest communication, and non-reciprocal communication, as factors that escalate conflicts between parents and schools (Lake & Billingsley, 2000). Given that parents of children with ASD already report higher stress levels, it is understandable that they may require more frequent or different types of communication than parents of typically developing children. When communication is limited, parents are not provided with the information they need to determine how their child is progressing compared to his/her peers and what supports or services they may need to address specific needs. Research suggests that parents often rely on communication with educators and service providers to help them make decisions about practices that will enable their child to become more independent across different education and social settings (Jindal-Snape, Douglas, Topping, Kerr, & Smith, 2005).
2.2.3 Planning and Decision-Making
Much effort has gone into providing information to parents of children with ASD on the importance of accessing early intervention services and quality education programs to help their child to achieve better long-term outcomes. Several websites and training packages (e.g. National Autism Center, 2011; Positive Partnerships, 2014) focus on providing parents with information on programs and practices that have a strong research base confirming their effectiveness for children with ASD. This has enabled parents to become aware of the positive outcomes that are possible for children with ASD. As a result, parents are beginning to question the appropriateness of support and practices for their child and are asking whether these programs will help their child reach their full potential. At the same time, parents report feeling pressured to make sure they access the best interventions available for their child, and worry that their child will suffer if they do not have access to these programs (Mackintosh et al., 2012). Parents utilise a variety of information sources to make decisions for their child, and often seek the recommendations of other parents or professionals to help them make these decisions (Deyro, Simon, & Guay, 2014; Miller, Schreck, Mulick, & Butter, 2012). Recently Carlon, Carter, and Stephenson (2014) found that parents cited advice from others as the most significant factor in influencing their decisions about interventions for their children.
Unfortunately, in a another recent study, mothers of children with ASD who attend mainstream schools (Lilley, 2015) indicated that teachers and school staff rarely provide parents with information about research-based practices. They report being provided with limited feedback about their child’s individual progress, and reveal that decisions about interventions have often been solely made by school staff without any consultation with parents. Stoner et al. (2005) also note that parents are viewed by school staff as being peripheral to the education decision-making process, and in some cases, as “obstacles or adversaries” to the process. Berquist and Charlop (2014) emphasise that parents are the most stable figures in their child’s
life. Teaching parents to choose and evaluate interventions for their child equips them with the tools they need to make empirically-based decisions about their child’s services, which in turn increases the outcomes for the child with ASD, their family and community. Although studies have suggested that parents may lack knowledge about evidence-based practices, recent research (Berquist & Charlop, 2014) suggests that when parents are provided with information and are supported to participate equally in education teams, they develop self-efficacy and are able to participate fully in decision-making processes and to select and implement effective strategies and supports for their child.
2.3
Parent Issues, Confidence and Need for Training –A Recent
Study
Recently, Australian parents were surveyed to determine the key challenges they faced in working with schools to plan and implement education programs for their children with ASD. Specifically, parents were surveyed about their experiences in negotiating with schools for their child; their confidence in assessing their child’s needs, setting goals for their child, and selecting interventions and evaluating outcomes for their child; and their needs for training and support that would increase their self-efficacy in these areas. Over the course of 4 weeks, 317 parents from across Australia completed the survey. The majority of respondents (56 %) were from the state of Queensland, with the next largest groups from New South Wales and Victoria (14 % & 13 % respectively). Parents also responded from South Australia (5 %), Tasmania (4 %), Western Australia (4 %), the Northern Territory (2.5 %), and the ACT (1 %).
Approximately 63 % of respondents had children in public state schools, but a surprisingly high number (13.4 %) reported they home schooled their children either on their own or under the guidance of distance education programs. A similar proportion indicated their children were attending Catholic schools. The majority of parents (70 %) reported their child had some type of individual education plan. Although 56 % of respondents indicated their child had accessed some type of early intervention service, 44 % stated that their child had not. This is a particularly significant finding as it suggests that school may be the first type of formal support and intervention that many children with ASD may be able to access. Respondents indicated their children were enrolled in a variety of school programs, with the majority (87.6 %) enrolled in a mainstream class on a full-time basis. Parents reported their children received support in the mainstream class both from teacher aides (35.1 %) or another teacher (20.9), however, 31.6 % of parents reported their child received no support. A few students (14.2 %) were enrolled part-time in a special education class and part-time in a mainstream class, and 17 % were enrolled full-time in a special education unit or school. Details on enrolments in education programs are provided Fig. 2.1. Participants indicated that the primary type of support their chil-
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corresponding to the temperature. It is doubtless within these limits that gliding can occur parallel to such planes as leave the molecules most room for the purpose, and which are directions of least resistance.
F . 119. Lehmann’s Crystallisation Microscope arranged for Projection.
Connected with this important question is the principle enunciated by Bravais, as a result of his discovery of the space-lattice, that cleavage occurs most readily parallel to those net-planes of the space-lattice which are most densely strewn with points. The force just referred to, whether we term it cohesion or otherwise, is obviously at a maximum within such a plane, and at a minimum in the perpendicular direction where the points are further off from each other. Moreover, it has been fairly well proved also, from the
experiments of Wulff, described in the last chapter, that the direction or directions of maximum cohesion are those of slowest growth of the crystal; so that faces parallel to those directions become relatively more extended owing to the more rapid growth of other faces on their boundaries, and thus become the most largely developed and confer the “habit” on the crystal. All these are facts so important as evidences of a controlling force at work in crystallisation, that a purely geometrical theory of the formation of crystals which would make “facility of fitting-in” of the molecular particles its chief tenet, obviously does not tell us the complete story. Hence the author desires to utter a warning against going too far with the pure geometry of the subject. The geometricians have done a grand work in providing us with the thoroughly well established 230 types of homogeneous structures, as a full and final explanation of the 32 classes of crystals, and so far their results are wholly and unreservedly acceptable.
The phenomena of “liquid crystals” lend themselves admirably to screen demonstration, for which purpose an excellent improved form of the crystallisation microscope of Lehmann, shown in Fig. 119, is constructed by Zeiss, and its actual use in the projection, with the aid of the well-known Zeiss electric lantern, but specially fitted for the purpose, is shown in Fig. 120.
A magnification of 600–700 diameters on the screen is very suitable, employing a Zeiss 8–millimetre objective without eyepiece. This objective affords directly a magnification of 30 diameters. For ordinary eye observation an eyepiece magnifying 6–8 times is added, thus affording to the eye a magnification of about 200 diameters.
F . 120. Zeiss Apparatus for the Projection of Liquid Crystals.
The lantern is supplied with a self-feeding electric arc lamp, ensuring a steady light. A collective lens of extra light-gathering power is fitted in front as condenser, and from it proceeds a lighttight tube provided with a water cell to filter out most of the heat rays which accompany the light. The electric lantern with Brockie-Pell or Oliver self-feeding arc lamp, shown in Figs. 71 and 79 (pages 186 and 202), is also equally suitable, and with the water cell, and parallelising concave lens removed from the large Nicol polariser, affords a parallel beam of the same character as the Zeiss apparatus. The microscope stands on a sole plate provided with levelling screws, and is naturally employed in the vertical position for such work with fused substances. A mirror inclined at 45° at the foot of the microscope directs the parallelised rays from the optical lantern through the microscope, and another above the optical tube reflects them to the screen.
The heating apparatus consists of a form of miniature Bunsen burner fitted with blowpipe blast, the respective pressures of gas and air being regulated by means of two taps with graduated arcs for obtaining greater delicacy of adjustment. The tabular plate seen to the left in Fig. 119 is the graduated semi-circle of the two taps; below it is seen the cylindrical mixing chamber for gas and air, in the event of the necessity for using the Bunsen as a blowpipe. There are two separate attachments for indiarubber tubes to this cylinder,
conveying respectively gas and air. Above the object stage a double air-blast is fitted, each tube of which is hinged with a universal joint, so that it can be readily adjusted to any desired position on either side of and above the glass plate (supported on little metallic uprights) on which the experiment is being conducted. A polarising Nicol prism and an analysing Nicol, both constructed in a manner which protects them from the effects of heat more effectually than is the case with the usual form, are provided for obtaining the projections in polarised light. The objective and analysing Nicol, as well as the substage condenser, are also specially protected from injury by heat, by being surrounded with a water jacket, supplied with running water, and a disc-like screen just above the objective assists in deflecting the heat rays from the optical tube and its Bertrand lens and other usual fittings. The miniature Bunsen flame is usually brought about an inch below the object-plate, and the size of the flame can be regulated with the utmost precision, so that a fairly constant temperature can be obtained for a considerable time. With the aid of the blowpipe air-blast temperatures up to 700° C. can be safely employed.
The microscope shown in position on the projection apparatus in Fig. 120 is a still more recent form introduced by Zeiss, embodying several further conveniences and improvements.
The following substances lend themselves particularly well to projection purposes. Para-azoxy-anisol with resin, which exhibits the phenomenon of rotating drops; cholesteryl acetate, which affords a fine example of spherical liquid crystals; paraazoxy-phenetol with resin, which gives beautiful interference colours; and the acetyl ester of para-azoxy-benzoic acid with resin, which shows the uniting of crystals to form larger and larger individuals.
Perhaps the most interesting and beautiful of all is cholesteryl acetate, a characteristic field of which is shown in Fig. 121 on Plate XVI., facing page 208. It is interesting that on this Plate XVI. there are represented the very hardest and the softest of crystals, namely, diamonds and liquid crystals. In order to obtain the finest effect the heating and cooling should be carried out very slowly. The little Bunsen burner, with a very minute flame, is first placed under the slide, and allowed to act until the substance melts and forms a clear liquid. The gas jet is then removed and the air-blasts, both of which
are simultaneously actuated when the tap controlling them is turned, are very gently brought into operation, one on each side of the centre of the slide, there being a good working distance of a quarter of an inch or more between the slide and the objective. The cooling is thus brought about very slowly. The Nicols should be crossed, and at this time the field is quite dark, the liquid substance being at this temperature (well above 114.5° the ordinary melting point) an ordinary singly refractive liquid.
As soon as the temperature has become reduced to that at which the particular modification of cholesteryl acetate is produced which forms liquid crystals, spots of light make their appearance at various points in the field, and each expands into a beautiful circular and more or less coloured disc marked by a rectangular sectorial black cross, which latter is well shown in the illustration (Fig. 121). These beautiful apparitions continue to occur, and each to expand to a certain size, which is rarely exceeded, until the whole field becomes filled with the wheels or crossed discs, the general effect very much in some respects resembling that afforded by a slide of the wellknown polarising substance salicine. These discs, however, are liquid, being spherical drops, of the structure already described and illustrated in Fig. 103, and that this is so is at once made apparent on touching the cover-glass with a pen-knife or other hard pointed substance, which immediately causes them to become distorted. They recover instantly their shape again when the pressure is removed. When the cooling, moreover, has proceeded still further, there is a sudden change, and acicular solid crystals shoot over the screen, tinted with all the colours of the spectrum, until the field is full of them, the ordinary solid modification of the substance having then been produced. The experiment may be repeated with the same specimen of the substance, mounted on the same slide, covered with the usual thin cover-glass, time after time for months, at reasonable intervals.
In concluding this chapter it may be mentioned that absolute proof of the double refraction of the liquid crystals of several different substances, derivatives of cinnamic acid, has been afforded during the year 1910. For direct measurements have been carried out by two independent investigators, Dorn and Stumpf, of the two refractive
indices corresponding to the ordinary and extraordinary rays in each case, the crystals being uniaxial.
CHAPTER XVII
THE CHEMICAL SIGNIFICANCE OF CRYSTALLOGRAPHY. THE
THEORY OF POPE AND BARLOW—CONCLUSION.
Nothing in connection with the subject of crystallography is more surprising than the neglect and apathy with which it has been for long treated by the chemical world. That crystalline structure is intimately related to chemical constitution will have been made abundantly plain during the course of this book. Yet in spite of the great work of Mitscherlich, essentially a chemist, and of a large amount of striking work which has been steadily accumulating during the last thirty years, with results of vital importance to chemistry, it is only at the eleventh hour that chemists are really awakening to the vast significance which crystal structure has for them.
The explanation undoubtedly is, that the long interregnum of conflicting investigations, doubt, and controversy, which followed the work of Haüy and Mitscherlich, and preceded the beginning of really accurate and painstaking investigation of an organised and systematic character, had caused chemists to regard with more or less of indifference the work of the crystallographers. Added to this we must remember that the subject of crystallography has hitherto been taught, when taught at all, merely as an appanage of mineralogy, although the pure chemical substances which crystallise well infinitely outnumber the naturally occurring minerals, and the results afforded by them frequently possess a much greater value by reason of the purity of the substances and their more definite chemical constitution. Also the mathematical and geometrical side has usually been unduly emphasised, and carried on in lectures without any practical goniometrical work at all. Moreover, the current text-books have often proved forbiddingly full of calculations
and formulæ, and of the obsolete and unenticing symbols of Naumann.
At last we have come to see that the subject is one of fascinating interest when its study is commenced in a practical manner from the beginning, armed from the very first lesson with the goniometer. The crystal itself is then our main and highly interesting study; its exterior form unravels itself in a most delightfully simple manner when we follow the arrangement of its faces in zones on the goniometer itself; and its symmetry becomes immediately patent to our eyes in all ordinary simple cases, when we construct for ourselves its plan in a stereographic projection, drawn at first in freehand while still at the goniometer. The calculations also become perfectly simple when we have learnt that only the simplest of the very easy formulæ of spherical trigonometry are required, and which a knowledge of only elementary plane trigonometry enables us to apply. Aided by a few very helpful rules, such as those of Napier for calculating right-angled spherical triangles, and the rule of the anharmonic ratio of four poles in a zone—which, when the positions of three crystal faces of the zone are known, at once enables us to calculate the situation of any fourth face of the zone—we have at once a stock-in-trade which carries us over all difficulties in the way of calculation, and relegates this side of the work to an altogether subordinate position, although accuracy in carrying it out is, of course, absolutely essential and even vital.
Especial interest has recently been attracted on the part of chemists to the bearing of crystallography on their science by a remarkable theory which has been advanced by Pope and Barlow, connecting the internal structure of crystals with chemical valency, the power which the atom of a chemical element possesses of combining with the atoms of other elements, and which is generally expressed by the number of atoms of a monad element, such as hydrogen or chlorine, with which it is capable of combining chemically. Thus the electro-positive metal potassium is said to have monad valency because it is capable of combining with one atom of the electro-negative element chlorine to form the salt potassium chloride, KCl; calcium possesses dyad valency because it can unite with two atoms of chlorine to form calcium chloride, CaCl2; aluminium is triadic as it can combine with three atoms of chlorine
producing aluminium chloride, AlCl3; carbon is a tetrad because it can take up four chlorine atoms, forming carbon tetrachloride, CCl4, and phosphorus a pentad as it can fix five with production of phosphorus pentachloride, PCl5; while sulphur is a hexad because it can take up as many as six atoms of chlorine, forming sulphur hexachloride, SCl6.
Occasion has already been taken in Chapter XI. to refer to the able work of Prof. Pope with regard to optically active carbon compounds, and in Chapter IX. the important contribution of Mr Barlow to the completion of the theory of the homogeneous partitioning of space has likewise been discussed. In collaboration these two investigators have now propounded a theory which connects the chemical and geometrical sides of crystallography in a somewhat startling manner, which has naturally aroused very considerable discussion, and which, whether right or wrong, cannot fail to have the best results in attracting investigators to the subject.
Starting from the facts which have now been laid down in this book as having been firmly established by the most careful measurement and experimental investigation—notably the constancy of the interfacial angles of the crystals of the same substance, the fixed positions of the atoms or their spheres of influence in the molecule and in the crystal, and the arrangement of the molecules in space-lattices and the atoms in point-systems—Pope and Barlow assume that valency, the expression of the relative combining power of the chemical elements, is a question of the size of the sphere of influence of the atom of an element, and that the relative sizes of such spheres of influence determine the modes in which they can be packed, that is, the nature of the homogeneous crystal structure which they can build up. The theory consequently renders the chemical phenomenon of valency and the physical phenomenon of crystalline form mutually interdependent.
It will thus be apparent that the essence of their conception is that the chemical molecule may be considered as made up of a number of spheres corresponding to, and representing, the spheres of influence of the atoms composing it, and that the volume of each sphere is roughly proportional to the valency of the atom which it represents. They then assume that the sum of the valencies of the atoms present
in the molecule may be substituted for the molecular volume, and the quantity thus arrived at is termed by them the “valency volume.” By using the valency volume instead of the molecular volume in the author’s formulæ for calculating the molecular distance ratios, which have been shown in Chapter X. to afford the relative dimensions of the unit cell of the space-lattice, and the distances of separation of the centres of gravity of the molecules from each other along the directions of the crystal axes, Pope and Barlow arrive at new ratios, which they term equivalence parameters. By the use of these latter they have attempted to account for the crystalline structure of a number of substances—chiefly organic compounds, in the investigation of which Prof. Pope has proved so adept—which are connected morphotropically in the manner described in Chapter VIII., and of others which are still less intimately connected.
Unfortunately, the equivalence parameters do not make clear the relationships in an isomorphous series, as do the molecular distance ratios; for they are, from their very nature and mode of derivation, almost identical for all the members of an isomorphous series, the valencies of the interchangeable elements being the same. The molecular distance ratios have also the great advantage of being derived from the three measurements which have now been brought to the highest pitch of experimental accuracy, namely, atomic weight determinations, density determinations by the Retgers immersion method, and goniometrical and physical measurements (optical and thermal) with instruments now available of the utmost refinement. Structural constants thus derived are obviously of especial value. It would thus appear that the theory requires modification so as to take account of the experimentally proved regular increase in volume and in the directional dimensions of the structural unit cell of the crystal space-lattice, when one element of the same family group and of the same valency is interchanged for another. Indeed, as the theory stands at present it entirely ignores and fails to offer any explanation of the highly important physical property of density, specific gravity. That this physical constant, and the equally important constant molecular volume, derived by dividing the molecular weight by the density, possess a real and significant meaning in isomorphous series, formed by the interchange of elements of the same family group, has been clearly proved in Chapter X. This fact is, indeed, so
obvious that any further development of the theory must of necessity take account of it.
A precise statement of their conception has recently been made by Prof. Pope in an excellent Report on the Progress of Crystallography, issued by the Chemical Society early in the year 1909. He states that they (Pope and Barlow) “regard the whole of the volume occupied by a crystalline structure as partitioned out into polyhedra, which lie packed together in such a manner as to fill the whole of that volume without interstices. The polyhedra can be so selected that each represents the habitat of one component atom of the material, and are termed the spheres of atomic influence of the constituent atoms. Up to this point no assumption is made other than that clearly indicated by the result of crystallographic measurements, namely, that each atom present in a crystalline structure exerts a distinct morphological effect—or, what is the same thing, appropriates a certain definite volume. The assumption is next made that the crystalline structure, which is resolvable into individual molecules and ultimately into individual atoms, exists as such by reason of equilibrium set up between opposing attractive and repulsive forces operating between the component atoms, and that this equilibrium results in the polyhedra representing the spheres of atomic influence assuming shapes which are as nearly as possible spherical.... The polyhedra thus arrived at may be regarded as derived by compression of a close-packed assemblage of deformable, incompressible elastic spheres,[29] the compression sufficing for the practical extinction of the interstitial space. When such an assemblage is released from pressure it is evident that in place of polyhedra, the shapes of which approximate as closely as possible to the spherical, closely packed spheres are presented; the distances between the sphere centres can be substantially in the same ratios as the distances between the centres of the corresponding polyhedra in the unexpanded mass, and the equilibrium condition of maximum sphericity of the polyhedra will be presented in the expanded mass of spheres by the existence of the maximum number of contacts between spheres. The whole method of treating the primary assumption thus resolves itself into finding close-packed assemblages of spheres of various sizes representing by their relative volumes the spheres of influence of the component atoms of any particular crystalline structure.”
Some very interesting evidence of the validity of their fundamental assumption of spheres of influence of the component atoms as the ultimate structural units is brought forward. They show that there are two modes of closely packing equal spheres, which give rise respectively to a cubic and a hexagonal crystal structure, the latter having a specific axial ratio of the vertical to the three equal equatorial horizontal axes; and that the chemical elements which are solids and crystallise, and the structural units of which can naturally be assumed to be equal spheres, being those of the similar atoms of the same chemical element, do practically all crystallise either in the cubic system or in the hexagonal system with the specific axial ratio indicated by them. The theory as it concerns chemical valency is obviously not affected by these interesting facts, as the spheres of influence present are those of the identically similar atoms of the same element. But the theory has received considerable support from the results of the investigation of a number of carbon compounds, chiefly derivatives of benzene.
Thus, in spite of the very wise decision of Barlow at the time of developing his theory of the homogeneous partitioning of space, to keep quite clear of attributing shape to the structural unit atoms or molecules, and to consider them as points, he, in common with the other contributors to that splendid geometrical work, appears driven to consider the question of shape when, in collaboration with his chemical colleague, he endeavours to apply his geometrical results to the practical problems of chemistry. It may be inevitable that we cannot get away from the idea of shape of the fundamental structural units. Yet the moment we do admit the idea, and begin to talk of polyhedra, or even of spheres, in close or any other packing, we enter the debatable land, concerning which the experimental evidence is as yet but shadowy and liable to many interpretations. Hence it is that we have the parallelohedra of Von Fedorow, having volumes proportional to the molecular volumes, the more general plane-faced cell of fourteen faces, the tetrakaidecahedron of Lord Kelvin and its deformed derivatives, and now the polyhedra of Pope and Barlow. The more indefinite “Fundamentalbereich” of Schönflies appears to be left behind, and we have embarked on a definite course of attributing shape to the component atoms or their regions of influence in the crystal structure. Von Fedorow has developed his particular theory in a very masterly manner, and with the aid of it
professes, and with very considerable success in many cases, to determine the correct mode of setting up a crystal for truly comparative descriptive purposes, and has derived therefrom a remarkable method of crystallochemical analysis.
Moreover, there is yet another view, that of Sollas,[30] that the packing of the molecules is a more open one altogether, a view to which he has been guided by consideration of the molecular volume. Sollas has offered some remarkable explanations of crystal structure, notably in the case of the dimorphous forms of silver iodide. The abnormal contraction which occurs on heating this interesting substance, and its sudden transformation at 146° from the ordinary hexagonal into a cubic modification as discovered by Lehmann, appear capable of very clear explanation on the basis of his theory. According to this theory of Sollas the volumes of the spheres of influence of the atoms of the different elements of the same family group, such as those of the group of alkali metals or those of the halogens, chlorine, bromine, and iodine, vary progressively in a manner which is dependent on the atomic volumes of the elements, which have a real comparative significance when the elements belong to the same family group.
It is probable that there is a considerable substratum of truth behind these various apparently conflicting views, and what is now required is that the germ of real fact shall be winnowed from the husk of fallacious speculation, just as occurred in the happy recent settlement of the old issue between Haüy and Mitscherlich. As in that case, moreover, it will be experimental work of superlative accuracy which can alone offer the desirable evidence on which a satisfactory arbitration can be founded.
It is thus obvious that we have now arrived at a stage in the history of crystallography when more experimental data, and many more measurements of the most carefully conducted character, on pure materials and excellently developed crystals, are most urgently needed, in order to decide these important, indeed fundamental, questions, the present state of which the author has endeavoured to present with judicial impartiality. When one looks around, and sees the almost complete lack of opportunities for the training of investigators in this rapidly growing branch of science, the importance of which to chemistry and physics is increasing every
day, while the field is ripe for the harvesters, one is inclined to feel depressed with the thought of the opportunities which are being lost. Our country has, in this science at any rate, a fine record, having with few breaks led the van of progress from the time of Wollaston, the inventor in the year 1809 of the reflecting goniometer, and of Miller, the originator of our method of describing crystals and the pioneer of accurate experimental work, down to the present day. It may be, also, that our country’s reputation is safe at this moment. But it is in the hands of a band of investigators so small, and often of the private and not professional nature, carrying on the work for sheer love of it and deep interest in it, that the wonder is that so much has been done, and it is the provision for carrying on our national tradition of leadership in crystallography in the future that is a matter for the deepest concern.
If the perusal of this book should have awakened sufficient interest in the minds of some of its readers to prompt them to offer themselves as recruits to this small band of investigators, and especially if it should have inspired the zeal and enthusiasm of a few young students looking around for a promising and fascinating field of work, and, finally, if it should prove to be of assistance in obtaining the means of training such recruits with the help of the best and most accurate experimental apparatus which can be obtained, the author’s main objects in writing it will have been attained.
Chromates and manganates, isomorphism with sulphates, 84
Classes, the 32 crystal, 6, 33
Cleavage, 17; and glide-planes, 275, 276
Cobalt sulphate, 78
Conditions for growth of crystals, 240, 244, 245
Constancy of crystal angles, 6, 13, 14, 17, 23, 132
Convergent light experiments, 186, 188
Copper sulphate, 40, 76, 78
Coppet, de, 238
Crookes, Sir William, 138, 208
Crossed-axial-plane dispersion of optic axes, 89, 94, 95; of ethyl triphenyl pyrrholone, 106, 107, 108; of gypsum, 89
Crystal, definition of, 4; germs and their influence on crystallisation, 236, 237
Crystals, modes of formation of, 4, 5
Cube and its perfection of symmetry, 38; axes of, 52
Cubic system, 37
Cyanide, potassium cadmium, crystals of, 42
Dalton, 25
Dark field of polariscope, 188, 202
Davy, Sir Humphry, researches on ammonia, 82, 83
Delafosse and morphotropy, 101
Deville and Troost’s researches on tantalum chloride, 84, 85
Diamond, 8, 137, 138, 207, 208
Dibenzal benzidine, liquid crystals of, 264
Digonal axis of symmetry, 36
Dimensions of structural parallelepipeda, 129
Dimorphism, 79, 87; of antimony oxide, 87, 88; of carbonate of lime, 79, 87; of mercuric iodide, 97; of sodium dihydrogen phosphate, 80, 81; of sulphur, 86; of vitriols, 79
Directive molecular force in crystallisation, 139, 269, 274–277
Dog-tooth spar, 10–12
Double refraction, interference colours due to, 176, 177; measure of, 169, 170; of biaxial crystals, 184; of uniaxial crystals, 183
Double sulphates and selenates, 35, 79, 121, 127, 128, 132
Dulong and Petit’s law, 84
Electronic corpuscles, constituents of atoms, 113, 124
Elements of a crystal, 68, 69
Enantiomorphism and optical activity, 140; 11 classes showing, 150
Epsom salts, 76, 78
Ethyl triphenyl pyrrholone, 105, 106
Eutropic series, definition of, 132
External molecular compensation, 134, 234
Extinction directions, 204, 205
Fedorow, von, discovery of remainder of 230 point-systems, 118, 119, 140; theory of, 291, 292
Ferricyanide, potassium, 44
Ferrocyanide, potassium, 43
Ferrous sulphate, 76, 78
Fletcher, indicatrix of, 184
Fluorspar, single refraction of, 206
Form, definition of a, 11, 60, 61
Frankenheim on morphotropy, 101;
discovery of space-lattices, 114
Frankland and Frew, 155
Fuchs, von, researches on sulphates of barium, strontium, and lead, 75, 77
Fuess reflecting goniometer, 64–66
Fundamentalbereich of Schönflies, 112, 113
Gattermann, 258
Gay-Lussac on alums, 77; on ammonia, 83; on racemic acid, 142
