Chemical Properties of Stannic Chloride. 391 



The solution of the alcoholate conducts with facility ; and 

 that electrolysis is proceeding is shown by a polarization- 

 effect of considerable magnitude. The electrolyte remains 

 clear and colourless. There were no signs of an evolution of 

 gas at the anode, and no tin was deposited at the cathode ; 

 but the difference between the electrolyte before and after the 

 passage of the current was shown by its behaviour towards an 

 alcoholic solution of mercuric chloride. The unelectrolysed 

 solution of the stannic chloride gave no precipitate of calomel, 

 but that through which the current had passed at once preci- 

 pitated calomel. In one experiment, when a concentrated 

 solution of the tetrachloride was electrolysed for two hours, 

 the whole was converted into a magma, and some of the solid 

 adhering to the electrode when dissolved in alcohol gave the 

 reaction for the stannous salt. In this experiment a copper 

 voltmeter showed that a current of between "1 and *15 of an 

 ampere had passed. 



The production of calomel in the electrolysed solution shows 

 that the current has transformed the stannic salt into a stan- 

 nous salt, stannic chloride into stannous chloride. The 

 absence of an evolution of chlorine gas is accounted for by 

 the certain action of electrolytic chlorine on the alcohol. 



Qualitatively it has been proved that alcohol added to 

 stannic chloride induces such a condition of instability as to 

 render it capable of electrolytic conduction. Moreover this 

 power of electrolytic conduction is closely analogous to the 

 power of sulphuretted hydrogen to precipitate stannic sulphide. 

 Mention has been made of the fact that the placing of a mere 

 film of absolute alcohol on one of the platinum electrodes 

 produces in the stannic chloride saturated with sulphuretted 

 hydrogen a slight conducting power and the precipitation of 

 stannic sulphide. When more alcohol is added, there results 

 a copious precipitation of stannic sulphide ; and when sul- 

 phuretted hydrogen is passed into the alcoholic solution of 

 stannic chloride an immediate precipitation of stannic sulphide 

 occurs. 



III. The Effect of Dry Ether. — Advantage was next taken 

 of the curious fact that ether combines with stannic chloride 

 to form a compound, SnCl 4 2(C 2 H 5 ) 2 0, which is soluble in 

 excess of ether. Absolutely dry ether was prepared in the 

 usual way. On adding the ether to the chloride a mass of 

 white crystals are formed, which are difficultly soluble in the 

 ether at the temperature of the laboratory. Ether was added 

 to the crystals and shaken ; the cell was then placed in circuit; 

 a deflexion of sixty scale-divisions was registered. But on 

 concentrating the solution by placing the cell in warm water, 



