MICROCHEMICAL REACTIONS OF CHROMIUM 
403 
A great excess of hydrochloric acid seriously reduces the 
delicacy of the reaction, while nitric and sulphuric usually pre¬ 
vent the separation of typical crystals. 
The student must bear in mind the caution given under anti¬ 
mony that cesium chloride has a strong tendency to form double 
salts, especially with lead, copper, cadmium, zinc, aluminum, etc. 
EXPERIMENTS. 
a. Try CsCl upon a solution of Sn in HCl. 
h. Try the test upon Sb in HCl solution; upon Bi in HCl solution. 
c. Try converting the chloro-salts of these three elements into the iodo com¬ 
pounds. 
d. Try testing for Sb and Bi in turn in the presence of a little Cu. 
e. Try mixtures in which some of the other metals are present which form 
crystallizable double chlorides with CsCl. 
D. Other Important Tests. 
With Primary Potassium Oxalate. (See Manganese, Method 
A, page 406.) 
With A mmonium Bichromate. (See Silver, Method B, p. 380.) 
CHROMIUM. 
Crystal Forms and Optical Properties of Common Salts 
of Chromium. 
A. ISOTROPIC. Chrome alums (I). 
B. ANISOTROPIC. 
Hexagonal. 
T etr agonal. 
Orthorhombic. - — Barium chromate (or M); calcium 
chromate (or M); potassium chromate; sil¬ 
ver chromate; sodium chromate; strontium 
chromate (or M); zinc chromate.^ 
Monoclinic. — Ammonium bichromate; ammonium 
chromate; barium chromate (or O); calcium 
chromate (or O); lead chromate; strontium 
chromate (or O). 
Triclinic. — Potassium bichromate; silver bichro¬ 
mate;- sodium bichromate. 
1 In the presence of FeS04- 7 H2O the salt separates monoclinic. 
* Ag2Cr207 dissolved in water decomposes into Ag2Cr04 and CrOs. 
