for gives appreciably lower values for the alkalinity of the more 

 concentrated solutions : — 



Soap. Sodium Palinitate. Potassium Palmitate. 



The hydrolysis of soap solutions above decinormal (3 per cent, 

 soap solution) is only a fraction of 1 per cent., and it is not very 

 different for sodium and potassium salts. The falling off in alkalinity 

 in concentrated solution is probably quite real, the chief experimental 

 error is in the opposite direction and the diminishing alkalinity is readily 

 accoimted for by the disappearance of the hydrolysable palmitate 

 ion to form ionic miceUe. The addition of sodium chloride also 

 dimhiished the alkalinity, which in this case, however, passes through 

 a minimum, since Avhenever a soap solution becomes heterogeneous, 

 its alkalinity becomes distinctly increased. Further measurments 

 show that the soap solution persists m being distmctly alkaline, even 

 in presence of large excess of palmitic acid. Thus an excess of 10 per 

 cent, palmitic acid reduces the alkalinity to two-fifths of that given 

 in the table, and even in presence of 100 per cent, excess of palmitic 

 acid the OH' is still 0-00004 N. It is very important to note that 

 even this slight degree of alkalinity precludes the existence of more 

 than minute traces of free fatty acid in any soap solution, so that 

 any solid product of hydrolysis can never be free fatty acid, but must 

 always be an acid soap, intermediate in composition between neutral 

 soap and NaHP.,, where P represents the fatty acid radical. 



It is equally important to note that when the excess of alkali is 

 added, it is not appreciably taken up bj' the soap present but remams 

 almost entirely in the free condition, in other words, basic salts 

 are not formed. 



If various fatty acids are compared it is found that degree of 

 hydrolysis increases rapidly as the homologous series is ascended. 



Influence of temperature again is important. The hydrolysis- 

 alkahnity decreases with lowering of temperature as, mdeed, would 

 have been expected. 



Very few measurements of the hydrolysis-alkalinity of commercial 

 soaps have been made, but the OH' concentrations of solutions made' 

 from soaps which were finished neutral, are usually less than that of 

 sodium palmitate. 



(6) Degree of Hydrolysis. 



Whilst the experimentally determined values of the hydrolysis 

 alkalinity, that is, the concentration of hydroxyl ions, seems to be 

 weU established, it is a matter of opinion how to interpret these in 



