Chemical Properties of Stannic Chloride. 387 



way, and then thoroughly dried by the use of tubes containing 

 calcium chloride and by a column of phosphorus pentoxide. 

 The gas thus carefully dried was passed for an hour into the 

 tetrachloride. The only alteration in appearance was due to 

 the separation of some white crystals, resembling in appear- 

 ance the hydrate SnCl 4 5H 2 0. After filtration the colourless 

 liquid, which smelt strongly of hydrosulphuric acid, and 

 fumed in the air as the original unaltered liquid does, was 

 tested for conductivity. But within the limit of these experi- 

 ments the conductivity was unaltered by the presence of the 

 hydrosulphuric acid. In striking contrast with this result is 

 the effect observed on merely placing a few drops of absolute 

 alcohol on one of the platinum electrodes, shaking it until no 

 more than a mere film adhered and then replacing it ; a de- 

 flexion is immediately registered and stannic sulphide is 

 formed on the electrode. 



These observations at once raised a question of considerable 

 chemical interest as to the nature of this nonconducting pro- 

 duct : had there or had there not been chemical action ? In 

 Watts' 'Dictionary of Chemistry' the following statement 

 is given on the great authority of Dumas : — 



" Stannic chloride quickly absorbs sulphydric-acid gas, 

 giving off hydrochloric acid, and forming a stannic sulpho- 

 chloride, 



SnS a . 2 SnCl 4 . 



The compound obtained by the perfect saturation with sul- 

 phydric-acid gas is a yellowish or reddish liquid heavier than 

 water. When heated it gives off SnCl 4 and leaves SnS 2 ." 



This abstract is in accord with the account of Dumas's 

 observations, given in Fremy's Encyclopedic Chemique. 

 According to these dicta, the answer to the above question 

 must be that there is chemical action. Assuming for a 

 moment that the statement is categorically correct and com- 

 plete, and that the liquid is indeed a chemical compound, 

 SnS 2 . 2 SnCl 4 , then even this compound is a nonconductor. 

 But this point is hardly worthy of expression ; because the 

 fundamental assumption, the existence of the liquid compound 

 SnS 2 .2SnCl 4 can be completely disproved. Attention was 

 directed to the following points in the above statement : — 



{a) " That sulphydric-acid gas is quickly absorbed and 

 that hydrochloric-acid gas is evolved." 



The idea is obviously that the following changes occur: — 



(1) SnCl 4 + 2 H 2 S = SnS 8 + 4HC1. 



(2) SnS 2 + 2 SnCl 4 = SnS 2 . 2 SnCl 4 . 



