W, G. Mixter — Heat of Combustion of Hydrogen. 227 



Calories. Calories. 



34498 D. 33937 Thorn. 16° to 20° 



34547 H. 33961 S. & W. 0° 



34414 G. 



34246 A. 20° to 22° 34061 Than 0° 



34219 F. & S. 6° to 12° 34495 B. 9° to 10° 



The most recent investigation of the specific heat of water 

 is that of Callendar and Barnes.* They regard the specific 

 heat at 20° as unity, and 1-0010 at 15°, 1-0022 at 10° and 10037 

 at 5° and the mean between 0° and 100° as 1-0014. These 

 data are used in reducing the calorimetric results to the water 

 calorie at 20°. Adding 14 to Thomsen's figures for reduction 

 to the calorie at 20° gives 33951. Allowing for the correction 

 he made for the interval between 18° and 20° and reducing by 

 formula 2, p. 221, Q = Q' + mt - mCjpt, in which Q'' is 33951 

 and t, is 16° and t 18° we have Q = 34031. Schiiller and 

 Wartha calibrated their ice calorimeter in terms of the mean 

 specific heat of water between 0° and 100°. Their figures are, 

 therefore, multiplied by 1-0014. Than calibrated his ice calori- 

 meter with silver and lead, using Regnault's specific heats of 

 these metals and also with water. His calibration is possibly 

 high. Omitting the figures of Dulong, Hess, Grassi and Ber- 

 thellot, which are obviously bigli, the results in the preceding 

 table reduced give the figures in the next table for the heat of 

 combustion of one gram of hydrogen at constant pressure and 

 formation of liquid water at 0° and in terms of the calorie at 

 20°. The writer's result, p. 226, is included. 



Andrews 34336 calories. 



Favre and Silbermann 34378 



Thomsen 34031 



Schtiller and Wartha 34009 



Than 34061 



Mixter 33993 



The first two are evidently high and should not be included 

 in the final value. Thomsen's value is the result of seven 

 experiments in which a total of 18 grams of water were formed 

 by burning hydrogen at constant pressure. Schiiller and 

 Wartha's value is the mean of five closely accordant experi- 

 ments and in each one about 1*3 gram of water was produced. 

 They burned electrolytic gases in a Bunsen ice calorimeter, 

 weighed the water formed and measured the heat, not with 

 the aid of a thermometer, but by the specific heat of water, 

 Than's value is the mean of the result of four experiments in 



*The Electrician, xliii, 775, 1899. 



