MICROCHEMICAL REACTIONS OF TIN 
393 
TIN. 
Crystal Forms and Optical Properties of the Common 
Salts of Tin. 
A. ISOTROPIC. — Tetraiodide (I); potassium chloro- 
stannate (I). 
B. ANISOTROPIC. 
Hexagonal. 
Tetragonal. 
Orthorhombic. — Tetrabromide. 
Manoclinic. — Stannous chloride + 2 H2O; stan¬ 
nous fluoride,* stannic chlorides. 
Triclinic. 
DETECTION. 
A. By Means of Cesium Chloride. 
Apply reagent by Method 7 , page 299. 
In testing for tin it is best to evaporate to dryness repeatedly 
with moderately concentrated nitric acid, thus converting the 
element into the insoluble dioxide. The dry residue is extracted 
repeatedly with dilute nitric acid to remove interfering elements 
and finally dissolved in aqua regia and the excess of acid removed 
by evaporation. Dissolve the moist residue in water. There 
is thus obtained a compound which we may term chlorostannic 
acid,^ with which cesium salts yield an immediate precipitate 
of cesium chlorostannate Cs2SnCl6 in the form of tiny colorless 
highly refractive regular octahedra and cubes. Rubidium gives 
a similar compound of greater solubility and therefore yielding 
larger crystals, but of sufficiently high solubility to render the 
separation of the crystalline phase too slow to be of practical 
use. These three chlorostannates are isomorphous. The am¬ 
monium salt is more soluble than the above and the presence of 
ammonium compounds is therefore objectionable; the same is 
true of sodium which yields Na2SnCl6-5 H2O. The latter salt 
1 This compound may also be regarded as a hydrated stannic chloride. If evapo¬ 
rated to dryness there will be obtained SnCl4-a:H20, where x is 3, 5 or 8. All three 
salts are crystalline and all can be referred to the monoclinic system. 
