134 



Dr. T. Ewan. On the 



difference were due to hydrolytic decomposition. The following 

 measurements of e show that again the opposite to this really occurs. 



Table VI. 



That some very small amount of hydrolytic dissociation takes 

 place is, however, probable. Dibbits* found that a solution of copper 

 acetate in the cold is very weakly acid towards litmus, and that on 

 warming it basic salts separate out, and on boiling the decomposition 

 into acetic acid and basic salt reaches about 50 per cent. The most 

 dilute solutions which I used did not deposit any visible quantity of 

 copper hydroxide on the porous vessel through which they were 

 filtered, and, even after standing for three days, the filtered solution 

 remained perfectly clear. The behaviour of the solutions of copper 

 acetate is, on the other hand, qualitatively at any rate, in agreement 

 ,-with the hypothesis that the substance is dissociated into ions. 

 Professor J. H. van't Hoff was so kind as to place the results of an. 

 unpublished set of determinations made by him of the electrical con- 

 ductivity of solutions of copper acetate at my disposal, for which I 

 take this opportunity of again expressing my indebtedness to him. 

 The numbers are given in Table VII. 



p.^ for copper acetate is calculated from Kohlrausch's numbers as 

 follows :/*, for JCnS0 4 atl4-l = 100'2. 



The difference between /* w J(K 2 S0 4 ) and ^KC Z H 3 Z at 14'l = 



30-4, 

 So that we get ^Cu^E^A), at 14'l = 69'8. 



It will be noticed that k remains constant till O35 of the salt is 

 dissociated, after which it diminishes. This behaviour reminds one 

 strongly of that of the dibasic acids studied by Ostwald ('Zeit- 

 schrift fur Phys. Chem.,' vol, 3, p, 170, 188l) ; the only difference is 

 that with the acids k finally increases instead of diminishing. It 



' Maandblad voor Natuurwetensckappen,' vol. 3, p. 80, 1873, and vol. 4. p. 101, 

 1874. 



