394 
ELEMENTARY CHEMICAL MICROSCOPY 
appears as irregular or thin rectangular prisms with parallel 
extinction and exhibits brilliant polarization colors. 
Iron, copper and antimony are apt to be adsorbed by the 
tin oxide; in such an event yellow or red double chlorides of 
copper or iron and cesium will eventually make their appearance. 
Occasionally if much iron is present the crystals of cesium chloro- 
stannate are colored yellow. 
Lead if present may give octahedra of cesium chloroplumbate, 
CS2PbCl6. 
As already noted, antimony gives hexagons and bismuth rhombs 
of the corresponding chloroantimonate and chlorobismuthate. 
In the event of no precipitate appearing after some time, add a 
fragment of potassium iodide. This may lead to the formation 
of cesium iodostannate, Cs2Snl6, of less solubility than the chloro- 
stannate. The iodo-compound separates in yellow cubes and 
octahedra.^ Yellow or orange cesium dichloriodide may form. 
In testing for tin in alloys it is usually sufficient to dissolve 
in nitric acid (i : i), evaporate to dryness, moisten with nitric 
acid and again evaporate to dryness. Extract the white residue 
with dilute nitric acid to remove interfering elements, dissolve 
in concentrated hydrochloric acid, drive off excess of acid, dilute 
and test. 
In order to obtain good crystals it is essential that the test 
drop be dilute before the cesium chloride is added. 
In the case of simple salts or mixtures it is usually sufficient to 
convert into chlorides by evaporating with hydrochloric acid; 
then dissolve in water, acidulate with hydrochloric acid and add 
the drop of cesium chloride solution. But in such an event one 
must remember that double chlorides of Sb, Bi, Cu, Fe, Al, Zn, 
Cd, Pb, etc., will almost invariably separate if present. 
If much tin is thought to be present use rubidium chloride in 
preference to cesium chloride. 
Note. — It is of considerable theoretical interest to note that 
in the compounds of the type just considered M2RCI6, M2RBr6 
and M2RI6, M may be K, Rb, Cs, (NH4) and R may be Se, Te, 
^ It is probable that the product actually obtained is a solid solution of Cs2SnI» 
in Cs2SnCl6. 
