W. G. Mixter — Carbon and its Heat of Combustion. 435 



iodide of starch paper white. Dense sugar charcoal decom- 

 poses the hot acid readily. Acetylene carbon absorbs only 

 about, 1/10 of 1 per cent of its weight of moisture from the air, 

 differing in this respect from charcoal. The determination of 

 density was made as follows : The carbon of the second series 

 of experiments was placed in absolute alcohol, which was then 

 boiled to expel air ; ethylene bromide was next added and the 

 boiling repeated v By successive additions of alcohol and bro- 

 mide a liquid was obtained in which the carbon remained sus- 

 pended over night. Professor Penfield kindly determined on 

 a Westphal balance the density of this liquid and found it to 

 be 1*919 at common temperature. 



First Series of Experiments. 



The bomb used for this part of the work was the one 

 described in this Journal, xii, 347, but with the addition of a 

 long narrow neck. Two determinations of the water equiva- 

 lent of the calorimeter at 20° gave 285 and 281*2 grams and 

 the equivalent calculated from the specific heats of the metals 

 was 284*7 grams. Since the fittings of the calorimeter varied 

 somewhat in the different experiments, the figures for the 

 water equivalent vary slightly. The carbon in a loose bulky 

 mass in the bottom of the bomb was ignited by the glowing 

 magnetic oxide which dropped into it when the iron wire 

 attached to the platinum electrodes was ignited by an electric 

 current. The combustion was explosive in character and com- 

 plete, and gave a temperature that fused the ends of the thick 

 platinum wires. The thermometer would rise perceptibly in 

 three seconds after passing the electric current. The oxygen 

 used was made from potassium chlorate and collected in a 

 glass gas holder over a dilute solution of potassium hydroxide. 

 In order to have the bomb fairly free from nitrogen it was 

 repeatedly exhausted and filled with oxygen and then the gas 

 was pumped in until the pressure was between 10 and 15 

 atmospheres. The weight of the oxygen was found by weigh- 

 ing the bomb before and after filling it with the gas. 



In the first three experiments the silver plating protected 

 the steel from oxidation, and the silver dissolved by the nitric 

 acid formed was not determined. For the remaining tests the 

 bomb was lined with a tight fitting shell of silver l ram in thick- 

 ness, and the silver dissolved was precipitated and weighed as 

 chloride. The heat of burning 1 mlg. of iron was considered 

 to be 1*6 calory. 



The air condensed on the surface of the carbon in the loose 

 form in which it was weighed for the various experiments was 

 found as follows : 



