SPECIFIC HEAT OF AMMONIA. 401 



perhaps to mention a little more in detail the work of Drewes, reported 

 by Dieterici.^^ 



Drewes used the Bunsen Ice Calorimeter in the range 0°-70° C. 

 He placed 0.5 grams of ammonia in a glass vessel w^hose volume was 

 1.2 cc. His results were expressed in terras of a calorie which appears 

 to have the value 4.187 Joules. He assumed that the specific heat at 

 constant volume w^as a linear function of the temperature, and gives 

 the following equation for c„. 



c„ = 1 . 118 + 0.00208 d O'' < ^ < 70° (36) 



w^here c„ is expressed in calories, and 6 is in degrees C. Dieterici 

 corrects only for the external work of liquid expansion in computing 

 the saturation specific heat of the liquid, and gives the follow^ing 

 equation for Cs2, '-^^ 



Cs, = 1. 118 + 0.00220 d 0° < < 70° (37) 



Dieterici gives only the approximate values of the volume of the con- 

 tainer and the mass of ammonia enclosed therein, so it is not possible 

 to apply Equation (27) to his equation for c„. The specific volume at 

 which his measurements were carried out was approximately 2.4 ccs./ 

 gram and hence the correction for the heat capacity of the vapor, the 

 heat of vaporization, and the expansion of the liquid would appear to 

 make his Cs2 less than c„ in the temperature region in which he operated, 

 rather than larger, as he states, so that it is probable that his quoted 

 values of c^j are too high, though how much too high it is not possible 

 to determine. 



The most accurate measurements of the specific heat of ammonia 



23 Dieterici, Zeit. f. d. Gesamte Kalte-Industrie. (1904), pp. 21, 47. 



24 The values given for the specific heat of ammonia by Landolt & Bornstein, 

 Physikahsch-Chemische Tabellen, 1905 Edition, are as follows: 



These values do not appear in the article by Dieterici, Reference 22, and 

 the writer has no explanation for their appearance in the Tabellen. 



