electrolyte in true solution, whereas in most aqueous solutions it is 

 of course a colloidal electrolyte. The conductivity is only moderate, 

 and the ebuUioscopic measurement indicates that it is a rather weak 

 electroljd^e. 



The great dissimilarity in the constitution of soaps in alcohol 

 and aqueous solution is brought out strikingly in an observation 

 of the writer. When alcohol is added to a clear aqueous solution of 

 sodium oleate the oleate is immediately salted out as a transparent 

 gel, although this readily dissolves again after a few minutes shaking. 



There are, however, colloidal projierties in alcoholic soaps which 

 require further investigation. Thus, although Miss Laing^^ has proven 

 that in solutions of potassium oleate in dry alcohol at boiUng point 

 there is no appreciable proportion of colloid present, yet sodium oleate 

 solutions, which have not yet been carefully studied in anhydrous 

 alcohol, are said to solidify to a gel on cooling ; and this would appear 

 to prove the presence of a large amount of colloid. Potassium oleate 

 on the other hand solidifies to a white curd on cooling. Oleic acid 

 itself in aU concentrations of alcohol is a simple electrolyte only veiy 

 slightly dissociated. 



III. — Hydrolysis, Hydrolysis- Alkalinity and Products of Hydrolysis. 



(a) Hydrolysis- Alkalinity. 



Until quite recently, the extent of the degree of hydrolysis and 

 the hydrolysis-alkalinity of soap solutions has been a moot point, 

 the estimates ranging practically from neutrality up to nearly complete 

 hydrolysis. This was due to the diflficulty of fmding a satisfactory 

 method of investigation, one which should not destroy the soap 

 solutions that were being subjected to measurement. 



The two methods introduced by McBam and Martin^^ and McBain 

 and Bolam^^ that of E.M.F. and rate of catalysis have suflBced to 

 establish that the alkalinity of soap solutions is very small, being of 

 the order of magnitude of 0-001 N free OH' for most concentrations 

 of soap. The E.M.F. method is of doubtful appUcation where 

 unsaturated compounds are present, as in the case of aU commercial 

 soaps, and the catalytic method is only appUcable in dilute solutions 

 at high temperatures. 



The hydrolysis-alkalinity of soap solutions depends upon the 

 concentration, the temperatures, the nature of the soap, and upon 

 its state of aggregation. 



Taking first the effect of concentration; in extreme dilution 

 hydrolysis is very appreciable, but once the concentration of soap 

 approaches decinormal, the hydroxyl ion increases but slowly with 

 future increase of concentration and passes through a flat maximum 

 shortly before normal concentration is obtained. 



The results obtained by E.M.F. in sodium and potassium soaps at 90° 

 are given in the following table in which aU concentrations are 

 expressed in weight normaUty. Diffusion potential was not taken 

 into account; a recalculation in which diffusion potential is allowed 



