RICHARDS. — HEATS OF COMBUSTION OF ORGANIC SUBSTANCES. 585 



of the bulbs was always found at the bottom of the crucible fused into 

 small globules. 



A peculiar nitrous odor was in some cases observed in the gas in the 

 bomb after a combustion. In order to discover whether this odor 

 might be due to the formation of small amounts of some of the oxides 

 of nitrogen which were not completely absorbed by the water, the fol- 

 lowing test was made on the gas in the bomb after combustions No. 12 

 and No. 25. The gas from the bomb was allowed to bubble slowly 

 through gas-washers made of test tubes containing cold distilled water. 

 This water was then boiled for some minutes to expel carbon dioxide, 

 and was then titrated with a very dilute sodium hydroxide solution 

 and phenolphthalein. The first drop of alkali turned the solution red, 

 so there must have been very little of the acid-forming oxides of nitro- 

 gen, nitric or nitrous acids in the gas. Any nitric oxide formed in the 

 bomb would have been immediately converted to nitrogen peroxide in 

 presence of the excess of oxygen, and would have dissolved in the 

 water. The washings of the bomb also were tested for nitrous acid 

 with a-naphthylamine and sulphanilic acid ; but negative results only 

 were obtained. In a number of other determinations under varying 

 conditions (Nos. 21, 22, 23, 24, 27), no odor whatever was noticeable 

 in the escaping gas, although the quantitative results were not essen- 

 tially different from similar ones in which an odor was noticed. Hence 

 it appears that whatever may have caused this odor, it has no appreci- 

 able effect on the heat of combustion of benzol ; no connection could 

 be found between the presence of the odor and the effect of increasing 

 the per cent of nitrogen present. Nevertheless the matter will receive 

 further attention in the future. 



The first trials of this method were from one cause or another unsuc- 

 cessful, as is usual in such cases ; but after eleven such partial failures 

 satisfactory results were regularly obtained. After a series of five 

 consistent values (Nos. 12-16) for benzol had been found, two com- 

 bustions (No, 17 and No. 18) were made in which the air in the bomb 

 was almost entirely removed before the oxygen was run in. It was 

 hoped that two advantages might be gained by conducting the com- 

 bustion in the absence of the nitrogen of the air originally contained 

 in the bomb : first, that the cause of the nitrous odor might be removed ; 

 second, that the correction for the formation of nitric acid would be 

 decreased. These new experiments gave for the heat of combustion 

 of benzol a value higher than the average previously obtained by over 

 0.3 per cent, — a greater deviation than could be ascribed to the errors of 

 the method. This interesting observation being new, so far as we could 

 discover, the matter was pursued further. Three more combustions 



