216 



Dr. J. H. Gladstone and A. Tribe. [Jan. 17. 



Before Electrolysis. After Electrolysis. 



Positive pole. Negative pole. 



(1.) S0 3 H 2 = S0 3 + H 3 

 (2.) S0 3 3H 2 = SO s + O s Hg 

 (3.) S0 3 ^HoO = S0 3 + O w H 3 „ 



But it was pointed out by Keuss, as far back as 1807, that when 

 electrolytic action occurs across a permeable diaphragm, a portion of 

 the liquid may travel from the positive to the negative compartment 

 of the compound cell by what is now called electrical endosmose. 

 Daniell and Miller ("Phil. Trans.," 1844) pointed out that in elec- 

 trolytic action there was also an unequal transference of the ions. It 

 is evident that each of these actions must introduce additional terms 

 into the formula with which Bourgoin worked. Moreover, Daniell 

 (" Phil. Trans./' 1839) investigated the electrolysis of sulphuric acid 

 of very different strengths by a similar method, and in a review of the 

 evidence (" Phil. Trans./' 1840) concluded that for each equivalent of 

 hydrogen liberated, the acid which passed across the diaphragm was 

 not more than one-fourth nor less than one-fifth of an equivalent. 

 Most of his experiments incline to the former. Did 2«, therefore, 

 represent the amount of sulphuric acid electrolysed, it would appeal' 

 from his results that tetra-, and not hexa-, basic sulphuric acid was 

 decomposed by the current. Again f Hittorf, in 1853 (vide Wiede- 

 mann's " Electricity," vol. ii, p. 589), observed that for one equiva- 

 lent of hydrogen liberated, the amount of sulphuric acid which was 

 found in the positive compartment varied, but not regularly, with the 

 strength of the acid. These discrepancies, both of observation and 

 deduction, led us to make some experiments on the subject ourselves. 



The apparatus we employed consisted of a LJ- sn aped tube of about 

 70 cub. centims. capacity, having a stop-cock in the centre of the 

 horizontal part. The vertical parts of the apparatus were divided 

 into millimetres, and the hole in the stop-cock packed with asbestos. 



