18 IF. G. Mixter — Thermal Constants of Acetylene. 



equation gave an average of 312990. Little significance is, 

 however, attached to the latter figure as the experiments from 

 which it is derived showed differences as great as 1-6 per cent. 

 Comparing the heat of combustion of acetylene with that of 

 its components plus the heat of dissociation we have : 



Calories 



Heat of combustion of 2-016 grams of hydrogen, 68440 



" " 24 " acetylene carbon, 189456 



" dissociation 26*016 " acetylene, 53879 



311775 



Heat of combustion of 26-016 grams of acetylene, 312677 



Difference, 902 



Since the explosions of acetylene under pressure and of 

 mixtures of this gas and oxygen are among the most violent 

 chemical changes known, producing a temperature of 2700° or 

 higher, the question arises, Is there any atomic disintegration 

 by which radio-active gases are produced? The calorimetric 

 results do not indicate that any thermal effect is due to such 

 change. The products of explosions were therefore tested in 

 an electroscope similar to the one described by Professor Bolt- 

 wood.* The fall of the gold leaf was observed with a micro- 

 scope. The experiments were as follows: Acetylene gas 

 collected over unboiled tap water caused a slightly greater leak 

 than air, as might be expected, since the waters of this locality 

 contain a radio-gasf. Accordingly gas from carbide was col- 

 lected over water which had been boiled an hour or two. 

 Acetylene containing a trace of phosphoretted hydrogen caused 

 no greater leak than air. The hydrogen resulting from an 

 explosion of such gas under pressure contained a phosphorus 

 compound and gave rather more leak than air. When, how- 

 ever, the acetylene was free from phosphoretted hydrogen the 

 hydrogen it yielded gave the normal leak. Repeated tests 

 made with the gas remaining after the explosion of a mixture 

 of acetylene and oxygen gave negative results. Freshly pre- 

 pared acetylene carbon produced in two experiments more than 

 the normal leak but the effect was slight. This may have been 

 due to ionization of the air caused by chemical change such 

 as the oxidation of the hydrocyanic acid adhering to the carbon. 



In conclusion it may be stated that no indication was found 

 of atomic disintegration or energy resulting except from ordi- 

 nary change. 



* This Journal, xviii, 97. f Bumstead, Ibid., xvii, 97. 



