Chemistry and Physics. 317 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Ammonium Bromide and the Atomic Weight of Nitrogen. 

 — A portion of the classical work of Stas upon atomic weights 

 has been repeated by Alexander Scott at the Davy Faraday 

 Research Laboratory of the Royal Institution in London. He 

 has worked chiefly upon the ratio between the weights of silver 

 and ammonium bromide. The materials used were prepared in 

 various ways with the greatest care, and it seems that the silver 

 and ammonium bromide used were even purer than the products 

 employed by Stas. The equivalent of ammonium bromide, com- 

 pared with silver as 107*93, from the average of a number of 

 closely agreeing results, was found to be 97*995, while Stas found 

 98-023. The difference, amounting to about one part in 3000, is 

 apparently most satisfactorily explained by supposing that Stas's 

 ammonium bromide contained a little impurity, probably plati- 

 num. Scott has made also two determinations of the equivalent 

 of ammooium chloride, and in this case also the result, 53-516, is 

 slightly lower than that of Stas, 53-532. When the molecular 

 weight of ammonium is calculated from Stas's value for ammo- 

 nium bromide and ammonium chloride, the results, 18*077 and 

 18-075, agree extremely well, but from Scott's results the numbers, 

 18*059 and 18*040, show a much less satisfactory agreement. 

 This discrepancy possibly points to the presence of an impurity 

 in the silver used for the present investigation, but this supposi- 

 tion is not very probable because Scott's ratio of silver to bromine, 

 as shown by the weight of silver bromide produced by a given 

 weight of silver, agrees exactly with that found by Stas. Further 

 work will be required to explain the matter. — Jour. Chem. Soc, 

 lxxix, 147. h. l. w. 



2. The Combustion of Gases. — The remarkable effect of small 

 quantities of propylene and other hydrocarbons in preventing the 

 explosion of detonating gas, which was observed by S. Tantar, 

 was mentioned in a recent number of this Journal (this vol. p. 86). 

 The same author has now published some further observations 

 upon the subject. 



A mixture of 1500 cc of detonating gas (2H 2 + 2 ) with 250 cc of 

 propylene, C 3 H 6 , was placed in a gas-holder. Upon allowing the 

 mixture to excape, it burned quietly in the air with a luminous 

 flame. When it was passed through a tube which was heated to 

 redness at one spot, the gas was ignited at the hot place and the 

 resulting flame moved slowly toward the inlet end ol the tube and 

 was extinguished at about 20 cm from the point of ignition. This 

 was repeated again and again as unburnt gas arrived at the 

 heated spot, but the phenomenon varied more or less according to 

 the rate of flow of the gas and the length of the heated part of 



Am. Jour. Sci.— Fourth Series, Yol. XI, No. 64.— April, 1901. 

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