32 Mr. W. Sutherland on Weak Electrolytes and 



10000. For butyric acid and water the equations are with 

 ^=0-9521, 



(A + pA? / '2)/p l p 2 p=0'089 from Pl = to 0-5. . . (23) 



=0-089 + 0'5(0'25-p lP2 ) 



from pi = 0-5 to 1. . . (24) 



These give p with a maximum error of 8 in 10000. For 

 neither propionic acid nor butyric do the data extend beyond 

 p l = 0'dl 1 so that it is not possible to say whether (22) and 

 (24) like (16) for acetic acid give a limiting value or A//? 2 , 

 when p 2 is small, which is rather less than the real limit. 

 From (22) for propionic acid the limiting value oE Ajp 2 

 is 0*2053, and from (24) for butyric it is 0*2037, which are 

 both close to 0*20G4 for the change of all the water into 

 hydrol of density 1*26. But equation (16) for acetic acid 

 gives A//9 2 = 0*2633 in place of 0*3072 from the more accurate 

 equation (19), so the values of A/p 2 just found from the 

 data for propionic and butyric acids may be in error in a 

 similar manner. It seems as though when acetic, propionic, 

 and butyric acids are added to water in small amount, they 

 first convert some of its trihydrol into dihydrol according 

 to the simple formulas (15), (20), (21), and (23), and then 

 when more acid is added, the conversion of dihydrol into 

 hydrol becomes prominent, being completed when the mix- 

 ture becomes a dilute solution of water in acid. 



The case of formic acid and water requires some special 

 attention on account of the known singularities of formic 

 acid as the first of the fatty series. The densities in Table III. 

 were found by Richardson and Allaire CAmer. Chem. Journ. 

 xix. p. 149, 1897). 



Table III. 



Contraction on making 1 gramme of mixture of Formic 

 Acid and Water at 20° (J. iFormic acid as liquid 1, 

 water 2, Pi = 1*2213, p 2 = 0*9983. 



100pi 12 3 4 5 6 7 



104p 10020 10045 10071 10094 10116 10142 10171 



104A 19 25 33 37 41 47 57 



10 4 (A+pA 2 /2)/> 1? ? 2 p 1910 1270 1130 950 850 820 86 



100^ 8 9 10 20 30 40 50 



\0 l p 10197 10222 10247 10489 10730 10964 1120 



104A 64 69 75 117 148 164 180 



104(A + P A 2 /2)/^ 2l o 850 820 813 703 661 627 649 



