366 Dr. J. Shields on Hydrolysis 



quantities of potassium hydrate and hydrogen cyanide, yet the 

 former is very largely dissociated into its ions. and. therefore, 

 in a particularly favourable state for entering into reaction 

 with the indicator, whilst the latter is not so. According to 

 the same theory, if we add other salts to a solution of hydro- 

 cyanic acid, which, per se. is only slightly electrolyrically 

 dissociated, then the amount of dissociation is diminished 

 many thousand times, and this is practically what occurs in 

 the solution under consideration. The presence of the un- 

 hydrolysed potassium cyanide causes the dissociation ratio of 

 the hydrocyanic acid to be vastly decreased. 



There are salts, on the other hand, whose solutions have an 

 acid reaction. This is due to the fact that the acid, which is 

 one of the products of hydrolysis, is more highly electrolyri- 

 cally dissociated than the base which is formed at the same 

 time. Usually the above facts are expressed by saying that 

 the base is stronger than the acid, or vice versa. 



If hydrocyanic acid were as nearly completely dissociated 

 as hydrochloric acid is. at the same dilution of course, then 

 probably a solution of potassium cyanide would be as nearly 

 neutral as one of potassium chloride, for Ostwald has pointed 

 out that all acids when completely dissociated are equally 

 strong. 



In this memoir, salts of strong bases with weak acids only 

 have been considered. The investigation was undertaken at 

 the suggestion of Dr. Svante Arrhenius. in Stockholm, and 

 the main object in view was the determination of the amount 

 of free alkali in aqueous solutions of such salts as potassium 

 cyanide, sodium carbonate. &c.; that is, of salts whose solutions 

 exhibit an alkaline reaction, or act as mild alkalies. 



I should like to avail myself of this opportunity to express 

 to Dr. Arrhenius my warmest thanks for the help which he so 

 willingly gave me and for the interest which he all along took 

 in the work. 



A research. " Zur Affinitatsbestimmung organischer Basen^ 

 (Zeits.f. physihal. Chemie. vol. iv p. 319. 1889 , on somewhat 

 similar lines, has already been carried out by Dr. James 

 Walker. In it the relative strengths of different organic 

 bases were measured ; but one of the experimental methods 

 which he adopted could have served equally well for the 

 determination of the amount of free acid in aqueous solutions 

 of salts of the bases. 



As a general rule, it will be found that the determination of 

 the amount of free alkali in solutions of the above salts is 

 beyond the scope of ordinary analysis. A reaction which 

 enables us to do so, however, is known. The velocity with 

 which the salt-solutions saponify methvl or ethyl acetate gives 



