Intelligence and Miscellaneous Articles. 2>11 



fulfils the foregoing condition, 



Pole = Current x Length. 

 It appears to me that Clausius's result must be accepted as the 

 correct one. 



Belfast, April 24, 1882. 



ON THE ELECTEOLYSIS OF DISTILLED WATER. 

 BY D. TOMMASI. 



Several physicists have questioned the possibility of decompo- 

 sing chemically pure water by means of a galvanic current. 

 According to M. Bourgoin*, water is not an electrolyte, the sub- 

 stance mixed with it to render it conductive is alone decomposed. 



The few experiments which I have made in regard to this sub- 

 ject have proved to me the contrary — that is to say, that water can 

 be electrolyzed even by the current of a very feeble battery, pro- 

 vided that the calories liberated by the battery are at least equal to 

 those absorbed by water in decomposing into its elements (about 

 69 calories). Those experiments are as follows : — 



(1) Into a U-tube filled with distilled water I introduce two pla- 

 tinum electrodes connected with two Daniell elements. The dis- 

 tance between the electrodes is about 2 centim. No visible effect 

 is produced, even after some time. The calories liberated by the 

 battery are nevertheless more than sufficient to effect the decompo- 

 sition of the water — in fact, 98>69. If, then, the water in this 

 case undergoes no decomposition, that is owing solely to the resist- 

 ance opposed by it to the passage of the current, and not to insuffi- 

 ciency of energy produced by the battery. 



(2) If in the preceding experiment the positive electrode be 

 replaced by a silver wire, this is what is observed : — After 18 hours 

 no appreciable alteration is noticed in the liquid ; but if, after 

 taking out the silver wire, a drop of hydrochloric acid be poured 

 into the branch in which it dipped, a very manifest white turbidity 

 makes its appearance, having all the characters of chloride of silver. 

 The hydrochloric acid does nothing more than precipitate the 

 minute quantity of oxide of silver which was dissolved in the dis- 

 tilled water. Now silver does not decompose water at the ordi- 

 nary temperature ; but, in order to produce oxidation, the water 

 must have been decomposed ; and consequently the distilled water 

 must have been passed through by the current. The electrodes in 

 this experiment were distant from each other about 7 centim. It 

 is evident, then, that, if the positive electrode is of silver, we can, 

 with the aid of two small Daniell elements, overcome the resistance 

 of a column of distilled water of 7 centim. length. 



(3) With three Daniell elements the effect is much more marked. 

 After 15 minutes it can already be ascertained, with the aid of hy- 

 drochloric acid, that the silver has begun to dissolve. At the end 

 of 18 hours all the curved portion of the tube is found covered 

 with a coat of oxide of silver, partly reduced by a secondary action. 



* Ann. de Chan, et de Phijs. [4] xv. p. 47, and xxviii. p. 119. 



