PHYSICAL CONSTANTS OF VEGETABLE PROTEINS 49 



Benedict and Osborne (29) have recently determined the heat of 

 combustion of a number of vegetable proteins which were prepared 

 with special reference not only to their separation from all non-protein 

 bodies but also from other associated proteins. These substances 

 were burned in the Berthelot-Atwater bomb. 



The calorimeter room was kept at the most constant temperature 

 possible, and all the minor precautions, suggested by experience with 

 over 10,000 of these combustions, were employed. 



The bomb used in these determinations was so adjusted, as regards 

 its hydrothermal equivalent, as to give the heat of combustion of pure, 

 anhydrous cane sugar as 3,959 calories per gramme and of pure, fused 

 benzoic acid as 6,322 calories per gramme. 



From 0*5 to 0*8 gramme of substance was used for each combustion, 

 which was weighed after the thoroughly dried material had assumed 

 constant weight by prolonged exposure to the air. 



The results of these determinations, calculated for I gramme of per- 

 fectly dry substance, are given in the following table : 



In general the higher heats of combustion are found for those pro- 

 teins which have a higher carbon content and similarly for those with 

 a lower oxygen content. Many irregularities, however, appear in the 

 preceding table, which are doubtless due to the different proportions of 

 the various amino-acids which constitute the molecules of the different 

 proteins. 



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