VOLUME CHANGES IN THE PROCESS OF SOLUTION. 85 



co-volume" which represents the additional volume occupied 

 by the molecule by virtue of its vibrations. The molecular 

 solution volume s y m may therefore be expressed by 



sV m = 2 n Fa + A 

 where 2 n F a is the sum of the atomic volumes and /_\ the 

 molecular solution co- volume, which Traube found to be 

 approximately constant for all classes of compounds, the 

 mean value at 15° O. being 12*4 ccs. Thus the following 

 val ues were obtained for atomic volumes at 15° 0.: — = 9*9 

 H = 31, 0(0H of COOH)= 0'4, 0(OH)= 2*3, O(0O)=5'5, 

 N = 1-5, A = 12*4. 



In the following table the values under <f> are those 

 determined experimentally (Tables IV — XII), and those 

 under s V m are the values calculated from the atomic 

 volumes at 15° O. (Traube). 



Table XIV. 



$ .Pm(15 8 -0.) 



Formamide (25° C.) HCONH 2 38-9 38-6 



Acetamide (30° C.) CH 3 CONH 2 55-8 54-7 



Propionamide (30° C.) C 2 H 5 CONFI 2 717 708 



Carbamide (25° C.) CO^Jg 9 44'4 43-2 



Succinamide (25° ) (CH a CONH a ) 9 89-4 908 



Succinic acid (25° C ) (CH a COOH) a 83 82-4 



Tricarballylamide (25° C ) 124-0 126-9 



The agreement between the experimental and calculated 

 values is satisfactory; the difference between the values 

 is no doubt due to the increase in value of A with tem- 

 perature. 



Solutions in ethyl alcohol. 

 The specific and molecular solution volumes of several 

 amides in alcoholic solution were determined at 30° C. The 

 results obtained are given in the following table. 



