44:0 W. G. Mixter — Carbon and its Heat of Combustion. 



over glowing copper oxide, and finally through a clear solution of 

 barium hydroxide. The barium solutions remained clear, In 

 the delivery tube in the second there was a faint white ring 

 indicating that the gas contained a trace of carbonic oxide. The 

 same result was obtained in subsequent experiments and is what 

 might be expected in a cooling mixture of oxygen, carbon dioxide 

 and carbonic oxide formed directly from the burning of the car- 

 bon and by the dissociation of carbon dioxide by heat. The 

 amount of carbonic oxide remaining in the bomb was, however, 

 too small to be estimated by ordinary methods or to have an 

 appreciable influence on the thermal result. 



The mean of the foregoing results is 7892* calories for one 

 gram of carbon. This is considerably less than other investi- 

 gators found for amorphous carbon and not much higher than 

 obtained for graphite. In order to find if the variation was 

 due to a constant error, sugar charcoal and graphite were 

 burned in the apparatus nsed for experiments 4, 5 and 6. 



Sugar Charcoal. 



The charcoal was prepared by charring sugar and heating 

 the coal for several hours in a Perrot furnace : next it was 

 heated for two hours in a current of chlorine, and finally it was 

 kept at a white heat for six hours. The product contained a 

 trace of chlorine and. 1/10 of 1 per cent of ash. The carbon 

 and hydrogen were determined with the precautions already 

 described. The following results are for the ash-free coal: 



I. II. Mean. 



Carbon 99'08 99*04 99*06 



Hydrogen 0-13 0-13 013 



Oxygen? _. (0-81) 



100-00 



The thermal results obtained, less the heat of combustion of 

 the hydrogen content, were 8028, 8023 and 8027, mean 8026 

 calories for one gram of carbon. Considering that 0-81 per 

 cent of the charcoal is oxygen in combination with hydrogen 

 we have 8057 calories. Neither method of allowing for the 

 hydrogen is to be considered as accurate, and the first correc- 

 tion is excessive. 



Graphite. 



Compact crystalline graphite associated with calcite was pul- 

 verized, digested with hydrochloric acid and washed. Thus 



purified it contained 0*32 per cent of ash. The analysis of the 

 combustible portion gave 



I. II. 



Carbon 99'90 99-89 



Hydrogen 0'01 0-02 



