Analytical Chemistry Department Faculty of Pharmacy Cairo University Analytical Chemistry – 1 [Course Code 602]
Research about
"Group IIB of Cations" Student Name: Ahmed Magdy Abd El-Baki Student Number: 50 Lab: B
Group 2B Arsenic subgroup The elements of this group are: ,
,
,
,
&
.
Separation: Residue of group 2B + 6-8 N HCl
Heat To Boiling
Continue Boiling For 5 minutes on small Flame Filter
Residue (Contains HgS & As2S5)
Filtrate (Contains SnCl4 & SbCl5)
The Separation of group 2B sulphides depends upon: 1. The Insolubility of Arsenic pentasulphide in HCl and its Solubility in ammonium carbonate:
is Slowly soluble in conc HCl upon prolonged boiling and the use of 6-8 N HCl is necessary. 2. The solubility of metallic tin and insolubility of antimony metal in HCl.
Upon treating the solution containing iron wire in presence of
,
with
(from HCl).
Black
째
Scheme for separation of group 2B Sulphides: Sulphides are reprecipitated by dropwise addition of HCl till acidic to litmus paper +
residue arsenic, tin and antimony sulphides
centrifugate discard
6-8 N HCl residue arsenic and mercuric sulphides
centrifugate ,
(đ?‘ đ??ť ) đ??śđ?‘‚
residue HgS dissolved In aqua regia, As before
Centrifugate thio and oxy salts of arsenic 1- acidify ďƒ yellow ppt. 2- magnesia mixture test Fe°
residue Sb° dissolved in
centrifugate tested by
ďƒ
orange ppt.
Identification and confirmations: Use the black HgS left after extraction of arsenic sulphide in ammonium carbonate HgS is dissolved in aqua regia and tested as before.
Arsenic Use ammonium carbonate extract thio and oxy salts of arsenic: 1. Acidify with Acid (Yellow ppt. of
or
)
Yellow ppt.
Yellow ppt.
2. Magnesia mixture test filter the precipitated sulphides
dissolve in conc.
evaporate the acid
render slightly alkaline with ammonia + magnesia mix.
White
Antimony 1. Sb° dissolved Dissolve the black residue (Sb°) in dil. Pass
(Orange ppt.)
2. Use the solution (containing the soluble chlorides of antimony ( ) and (no addition of iron wire) The Solution Render slightly alkaline with ammonia Add 5-6 g of oxalic acid + 50 ml water Boil until dissolve Pass
for 3 minutes
(Orange ppt.) N.b: Oxalic acid forms very stable complex with tin, So when is passed only ( ) is precipitated.
Tin 1. Use the filtrate (obtained after reduction of iron wire) The filtrate
Add 2-3 drops of
White
ppt. (may be gray or black Hg째)
2. The solution Containing tin-oxalic acid complex (antimony, test no. 2) Evaporate the solution with conc. and conc.
Cool Make slightly alkaline with ammonia Make slightly acidic with HCl Pass
Yellow ppt. of