and of Combustion of Acetylene, Ethylene and Methane. 349 



most of them not a trace was detected. The pressures used 

 were higher than those at which the gas was exploded in 

 earlier experiments,* when several per cent of acetylene was 

 found after exploding. Whether the different result in this 

 respect is due solely to pressure or to other causes, the writer 

 has not had time to investigate. In order to find if the acety- 

 lene decomposed in the calorimetric bomb without formation 

 of hydrocarbons, the following tests were made. The gas in 

 the bomb after an explosion was passed through a solution of 

 potassium hydroxide to remove hydrocyanic acid and then 

 burned. No carbon dioxide was revealed by lime water. 

 2*4 grams of carbon from the acetylene exploded in the bomb 

 were heated in a combustion tube through which a current of 

 dry air was passed to remove moisture. The combustion was 

 then made in the ordinary way with oxygen and copper oxide. 

 The result was 0*016 per cent of hydrogen. This amount may 

 be due to the error of the analysis. These results show that in 

 the calorimetric experiments the acetylene decomposed com- 

 pletely into hydrogen and carbon. 



The composition of each sample of gas used was determined, 

 and the amount taken was calculated from the capacity of the 

 bomb or was found by weighing the bomb before and after 

 filling : when hydrocyanic acid was estimated in the residual 

 gas an equivalent quantity of acetylene was deducted from 

 that taken. As a rule, the description of the many details 

 involved in finding the amount of gas used for an experiment 

 are omitted. Since the accurate determination of differences in 

 temperature is the most difficult problem in calorimetry, the 

 observations are stated in detail. The water in the calorimeter 

 was stirred by the small screw propellers shown in the figure, 

 driven by a motor. The observations of temperature were 

 recorded at intervals of three minutes, and that noted imme- 

 diately before explosion is taken for the initial temperature, no 

 correction being made for slight changes preceding. The final 

 temperature assumed is that observed the sixth minute after 

 explosion plus five-sixths the average fall in temperature for a 

 subsequent six minutes. The reason for not allowing for loss 

 of heat during the first minute is this : the water of the calori- 

 meter did not attain the maximum temperature observed until 

 one, two or sometimes three minutes after the explosion, and it 

 is less accurate to consider that as much heat is lost by the 

 calorimeter in the six minutes immediately following explosion 

 as in the next six. It is possible the corrections made are 

 excessive, but any error in this respect is small as the correc- 

 tion in but a few instances amounted to one per cent, and 

 in most of the experiments it was less than half as much. 

 *This Journal, ix, 1, 1900. 



