404 
ELEMENTARY CHEMICAL MICROSCOPY 
DETECTION. 
A. In simple salts we may obtain the following colors and 
reactions: 
a. Soluble chromates are yellow, bichromates red, their solutions 
yellow. Solutions of chromium salts where chromium acts as a 
base, when heated in acid solution, are green. 
b. Chromium yields with ammonium hydroxide a bluish or 
greyish green or greyish lavender hydroxide. In the presence 
of ammonium salts, especially ammonium chloride, this hydrox¬ 
ide is partially soluble with the formation of the compound 
CrCb • 4 NH3. Boiling drives off the ammonia and chromium 
is completely precipitated as Cr(OH)3. 
c. Silver nitrate gives in solutions weakly acid with nitric acid 
a characteristic deep red chromate with both chromates and 
bichromates (see Silver, Method B, page 380). In neutral solu¬ 
tions silver nitrate gives a precipitate with chromates some¬ 
what more readily than with bichromates, but the difference 
is too slight to be of any practical use in differentiating between 
the salts. 
d. Alkali chromates added to neutral solutions of manganous 
salts give a characteristic manganous chromate, but alkali bi¬ 
chromates give no such reaction (see Manganese, Method B, 
page 407). 
B. By Conversion into Cesium Chrome Alum. 
To a drop of the solution to be tested add ammonium 
hydroxide. Should a reddish liquid result, boil. Decant the 
solution from the bluish or greenish precipitate. Wash the pre¬ 
cipitate once or twice. Add a tiny drop of water and then very 
carefully the least possible amount of dilute sulphuric acid which 
will just dissolve the precipitate. Evaporate carefully nearly to 
dryness and add a tiny drop of water. Finally introduce near 
the center of the drop a fragment of cesium sulphate. Cesium 
chrome alum will almost immediately separate in characteristic 
alum crystals, the octahedron and dodecahedron predominating 
(isometric). These crystals have a faint bluish tint by trans¬ 
mitted light. The peculiar purple color of chrome alum will 
not be seen unless they attain a relatively large size and reflec- 
