RICHARDS. — HEATS OF COMBUSTION OF ORGANIC SUBSTANCES. 589 



case of benzol has not been determined ; solid carbon, at least, was 

 wholly absent. 



Those determinations in which the least nitrogen was present un- 

 doubtedly represent the closest approach to the true value for the 

 heat of combustion of benzol. The first average of five determinations 

 in the presence of about 3 per cent of nitrogen gives 2.662° as the 

 rise in the calorimetric system for 1 gram of benzol. This, in our 

 opinion, represents a minimum value ; the true one may be yet higher. 

 It is planned to determine soon the heat of combustion of benzol in the 

 presence of pure oxygen. 



Obviously, data on only two substances will not permit the drawing 

 of certain general conclusions. Nevertheless, it seems reasonably prob- 

 able that the effect in general of the presence of an inert gas during 

 the combustion of easily burned substances is very slight. On the other 

 hand, other substances like benzol which need much oxygen for their 

 combustion are probably, like it, affected by the presence of an inert 

 gas. 



Since the water-equivalent of our bomb and calorimeter has not 

 been determined either by the method of finding the sum of the 

 water-equivalents of the component parts, or by the admirable electri- 

 cal method of Jaeger and von Steinwehr,^ absolute values for the 

 heats of combustion of sugar and benzol cannot be computed from 

 these data. Until an accurate value for the absolute heat of combus- 

 tion of some standard pure substance has been obtained, the present 

 results may be expressed as ratios, taking the rise in temperature of 

 the calorimetric system caused by the combustion of one gram of cane- 

 sugar as the standard of reference. Such ratios can be easily con- 

 verted to absolute values when a standard has been established, and 

 moreover, the relative values can be used to the same purpose as ab- 

 solute values in the application of heats of combustion to the primary 

 idea which instigated the present work. The outcome of the present 



work is thus that a gram of benzol yields at least , ' . , . = 2.5342 



l.OoOi 



times as much heat on combustion as a gram of sugar. 



It is interesting to compare this result with the results of other 



experimenters. On account of the relation which exists between the 



weight of water and the weight of metal in the bomb-calorimetric 



system, and the fact that at temperatures between 0°-30° the specific 



heat of water decreases, while the specific heats of the metallic parts of 



» Verhandl. d. d. pliysik. Ges., 5, 50 (1903) ; Ibid., 5, 353 (1903); Zeit. phys. 

 Chem., 53, 153 (1905). 



