402 
ELEMENTARY CHEMICAL MICROSCOPY 
B. ANISOTROPIC. 
Hexagonal. — Sulphate (9 H2O). 
Tetragonal. —Bismuthyl chloride. 
Orthorhombic. 
Monoclinic. 
Triclinic. — Nitrate (?); bismuthyl nitrate. 
DETECTION. 
A. The Addition of Water to neutral or very faintly acid so¬ 
lutions followed by the formation of a heavy white amorphous 
or granular precipitate should lead to the suspicion of the 
presence of bismuth. From the chloride, the compound BiOCl 
is obtained and from the nitrate BiONOs • H2O. 
B. By Means of Potassium Sulphate. 
This test has been discussed at length under Sodium, 
Method B, page 322, and also under Potassium, Method B, 
33O) to which the student is referred for details. 
Neither arsenic, antimony, nor tin yield a crystalline deposit. 
The test is therefore one of the most satisfactory for the recog¬ 
nition of bismuth, providing lead is absent. Lead yields a gran¬ 
ular or amorphous (or rarely crystalline) precipitate with potas¬ 
sium sulphate. It is therefore necessary to first remove the 
lead by precipitating with sulphuric acid in the presence of 
nitric acid before proceeding to test for bismuth. With this 
end in view add to the solution to be tested nitric acid, then a 
drop of very dilute sulphuric acid — if no precipitate results, 
evaporate until fumes of sulphur trioxide are formed. Then 
proceed as described under Method 77 , page 300, Experiment a. 
If a precipitate forms with the sulphuric acid decant, centrifuge 
or filter the solution to remove the lead, after which evaporate 
with sulphuric acid and proceed as above. 
C. By Means of Cesium Chloride. 
This test has already been discussed under Antimony, 
Method A, page 398. 
The only specific difference between the double chlorides of 
these two elements is that with bismuth there is a greater ten¬ 
dency toward rhombic plates. Conversion into double iodides 
gives a salt darker colored than that with antimony. 
