1128 Journal of Applied Microscopy 



Make a mixture of Na, K, Ca, and a trace of Rb, and test. Repeat the last 

 experiment, after having introduced Cs. 



///. Stannic Chloride. 



Solutions of stannic chloride added to hydrochloric acid solutions of cesium 

 salts give rise, even in dilute solutions, to the precipitation of cesium chlorstan- 

 nate Cs2SnCl,;. 



In order to avoid the possible interference of other salts, it is advisable to 

 first convert the substance to be tested into the form of a chloride by repeatedly 

 evaporating with hydrochloric acid. 



Place near a drop of the moderately dilute solution of the substance, prev- 

 iously acidified with hydrochloric acid, a drop of a concentrated solution of the 

 reagent, also acidified with hydrochloric acid. Cause the drops to unite. Cesium 

 chlorstannate is almost immediately precipitated as colorless transparent crystals. 

 The usual forms obtained are the cube, octahedron, and combinations of the two. 

 In fact, crystal forms identical with those spoken of in the discussion of potassium 

 chlorplatinate (q.v.). Fig. 29 will, therefore, also represent the appearance of 

 these crystals. 



Ammonium salts must first be removed by gentle ignition, since ammonium 

 chlorstannate is a salt of almost as low solubility as that of the corresponding 

 cesium compound. 



The chlorstannates of potassium and rubidium are much more soluble than 

 that of cesium, hence there is little danger of their separating from dilute solu- 

 tions. If, however, the solution employed has not been of sufficient dilution, the 

 rubidium salt RbgSnCl^ will first separate in forms identical with those of the 

 cesium salt, but of slightly larger size, then after a time, when the drop has 

 evaporated sufficiently, the potassium salt K2SnClg will also appear in yet larger 

 crystals. 



If iron is present in any considerable amount the crystals of cesium chlor- 

 stannate which separate are generally colored yellow. 



The sodium salt Na2SnCl,5 • SHgO is too soluble to separate under the con- 

 ditions which obtain in the test. The same is true of the chlorstannates of the 

 calcium group. 



In cases where no crystals of the cesium salt appear after some time, a little 

 sodium iodide can be added, thus inducing the formation of cesium iodostannate, 

 which is considerably less soluble than the chlorstannate. Cesium iodostannate 

 appears as tiny lemon or orange-yellow octahedra. 



In the place of stannic chloride, the chlorides of the closely related elements, 

 antimony and bismuth, can be employed, either with or without the addition of 

 sodium iodide. Thus, chlor- or iodo- antimonates or bismuthates are obtained. 

 The iodo- compounds thus produced yield very beautiful reactions. 



Exercises for Practice. 



To chlorides, in HCl solution, of Na, K, Rb, Cs, NH^, add stannic chloride, 

 first trying the reaction on concentrated, then on dilute solutions. 



Make a mixture of K and Cs, test. Then try one of Rb and Cs. 



Try the reaction of chlorides of bismuth and of antimony on cesium chloride. 

 Chemical Laboratory, Cornell University. E. M. ChamOT. 



