or "Avidities" of Weak Acids. 161 



between two acids, so we may write 



g (KOH x HON) = KON x HOH. 



Instead of the K of the former paper we must therefore 

 use its reciprocal ^. 



In Table I. the strengths of the acids in tenth-normal 

 solution have been compared ; that of hydrocyanic acid being 

 arbitrarily taken as unity. The values of K are taken from 

 the paper on hydrolysis (loc. cit.). 



Strictly speaking only the monobasic acids are comparable ; 

 but in order to form some conception of the order of magni- 

 tude of the relative strengths of carbonic and biboric acids, 

 the characteristic constants have been halved and the calcula- 

 tion proceeded with in the ordinary way. 



Table I. 



Xame of acid. 



K. 



P. 



28-8 ' 



Hydrocyanic acid 



1204 xlO-* 5 

 668xl0~ 10 

 925 x 10 -5 



1954 x!0~ 5 

 50 X 10~ 5 



28-8 

 3869-1 

 10-4 

 10-1 

 63-2 



1 

 134 

 036 

 0-35 

 22 



Acetic acid 



Carbolic acid 



Carbonic acid 





The great difference between acetic acid and the others is 

 very remarkable. A still better idea of the relative strengths 

 of these weak acids is obtained when they are compared with 

 some of the stronger acids. Hydrochloric acid together 

 with the three chlorinated acetic acids seem specially well 

 adapted for this purpose, as they supply different grades of 

 strength. The values attached to these acids are taken from 

 Ostwald's tables, and are calculated from the velocity of 

 catalysis of methyl acetate by half-normal solutions of the 

 acids. 



Table II. contains a list of the acids arranged in their 

 relative order of strength. 



Phil. Mag. S. 5. Vol. 37. No. 224. Jan. 1894. M 



