Chemical Properties of Stannic Chloride. 385 



forty volts would give this deflexion through a resistance of 

 forty megohms. Thus, then, the lower limit to the value of 

 the conductivity of the above column of pure stannic chloride 

 cannot be less than one thousand and six hundred megohms. 

 There is thus in this chemically homogeneous liquid a high 

 degree of insulating power, and one admirably adapted for 

 the study of the influence on its electrical conductivity of the 

 destruction of that homogeneity. The agents used to produce 

 the required heterogeneity may be classified : — 



A. Dry gases. 



B. Liquids. 



C. Solids. 



Class A. The Effect of Dissolved Gases on the Conductivity. 



I. Chlorine Gas. — A specimen of stannic chloride of a yellow 

 colour was prepared as above, save that the excess of chlorine 

 was not removed by granulated tin. The experiments above 

 described, using the yellow liquid with the excess of chlorine, 

 were again performed, and precisely the same results were 

 obtained ; so that the dry chlorine gas was without effect on 

 the conductivity. It will suffice to note that no compound of 

 tin and chlorine exists in greater proportion than one atom of 

 tin to four atoms of chlorine. 



II. Dry Hydrochloric-Acid Gas. — The hydrochloric acid 

 was carefully dried by sulphuric acid. It was then passed 

 for a quarter of an hour through a V-tube containing the 

 tetrachloride. An absorption of the gas was indicated by the 

 fall in temperature of the liquid through four to five degrees, 

 which may, however, have been due to the evaporation of the 

 stannic chloride, and on tightly corking both arms of the 

 V-tube the liquid rose to different levels. 



The accompanying diagram illustrates the arrangement of 

 apparatus which I used both here and in subsequent experi- 

 ments to detect the existence of a polarization effect. The 

 battery used to electrolyse this tetrachloride saturated with 

 hydrochloric-acid gas consisted of twenty-five storage-cells. 

 On making the primary circuit, a small direct current passed, 

 producing a deflexion of thirty scale-divisions. The cell had 

 thus a resistance of above 5 x 10 7 ohms. Calculating from the 

 magnitude of this direct current, it was not to be expected 

 that a polarization-current would be observed: in fact, after 

 passing the primary current for half an hour, no current was 

 detected on making the secondary circuit. 



