TRANSACTIONS OF SECTION B. 



319 



The greater number of the above tests are valueless when applied to mixtures 

 of petroleum and coal-tar naphthas, but No. 10 is capable of giving quantitative 

 results if the treatment with nitric acid be conducted in a small flask and an 

 inverted condenser attached, to prevent loss of vapours. When action has nearly 

 ceased, if the liquid be poured into a narrow graduated tube, the measure of the 

 upper layer indicates with approximate accuracy the amount of petroleum spirit 

 present. If the proportion of benzene is considerable, the nitrobenzene produced 

 may not remain completely dissolved in the nitric acid, in which case it rises and 

 forms a layer of a dark brown colour below the stratum of petroleum spirit. Nitro- 

 benzene and petroleum spirit are readily miscible in the absence of nitric acid, but 

 agitation with strong nitric acid dissolves out the nitrobenzene, a portion of which 

 may rise and form an intermediate layer as above described. 



By fractional distillation, the author found that the proportion of heptane, 

 C 7 H 16 , present in commercial benzoline probably equalled, or even exceeded, that 

 of all the other constituents. 



9. On the Illuminative Value of a Mixture of Hydrogen with some Hydro- 

 carbons. By A. Yeknon Haecourt, M.A., F.B.S., Lee's Reader in 

 Chemistry at Christ Church, Oxford. 



The author has determined the proportions in which pentane and hydrogen 

 must be mixed to form a gas which, burnt at the rate of 5 cubic feet an hour at 

 a standard argand burner, gives the light of 16 candles. He has also made a 

 comparative experiment with benzene. 



The experiments were made by passing hydrogen from a gasholder into a 

 cylindrical glass about an inch wide, containing the volatile hydrocarbon, and thence 

 though a meter to the burner. By regulating the temperature of the liquid, and 

 the distance between the mouth of the tube through which the hydrogen entered 

 and the surface of the liquid, the light of the gas flame upon the disk of the photo- 

 meter could be kept nearly equal to that of the candles used for comparison when 

 the gas was passing through a meter at 5 cubic feet an hour. 



Each experiment lasted one hour, at the end of which the weight of pentane 

 which had evaporated was ascertained, and the weight of spermaceti consumed by 

 the two candles. An observation of the illuminating power of the gas was made 

 every minute, and the rate of evaporation adjusted so as to keep the illuminating 

 power as nearly as possible equal to that of 16 candles. 



The following results were obtained : — 



The weight of pentane burnt is corrected proportionally from what it was with 

 the actual illuminating power obtained, judged by the light actually given by the 

 candles, to what it would have been if the gas had given the light of 16 candles 

 each burning at the rate of 120 grains per hour. 



The weight of pentane required to maintain this light for one hour is 40-6 

 grams. The mixture consisted of 4-55 cubic feet of hydrogen, and 0-45 cubic foot 

 of pentane. Thirty-nine grams of pentane burnt with this proportion of hydrogen 

 under the conditions of the experiment yield as much light as 120 grains of 

 spermaceti burnt in a candle. 



