Chemistry and Physics. 475 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Mass of a Liter of Normal Air. — The mass of oxy- 

 gen in the air at Sorbonne has been found by Leduc to vary 

 irom 23*14 to 23*20 percent; and since this difference corre- 

 sponds to a tenth of a milligram in the mass of a liter of air, he 

 regards it as useless to attempt any higher degree of accuracy in 

 such determinations without at the same time determining the 

 composition of the air examined. He finds that the mass of a 

 liter of the average air at Paris, at 0° and 760 mm is 1*29315 gram. 

 Defining normal air to be air collected on a plain in calm weather 

 at a distance from a town, which contains a little more than 23*2 

 per cent of oxygen by mass or almost precisely 21*0 per cent by 

 volume, the author finds that the mass of a liter of such air at 0° 

 and 750 mm is 1*2932 grams; and at 0° and under one c. g. s. atmo- 

 sphere, 1*2758 grams. In estimating the densities of gases, he 

 prefers to take nitrogen as the standard because, not only is it 

 readily procurable in a state of purity but it has a density so 

 nearly that of air that no appreciable error is caused by the 

 presence of a small quantity of air in the apparatus. The mass 

 of a liter of nitrogen at Paris under normal conditions is 1*2570 

 grams; its mass under a pressure of one c. g. s. being 1*24006 

 grams. — C. P., cxvii, 1072, December 1893. g. f. b. 



2. On the Preparation of Nitrogen monoxide. — It has been 

 observed by W. Smith that a mixture of ammonium sulphate 

 and sodium nitrate, kept at 215° for two or three hours, decom- 

 poses for the most part into sodium sulphate and ammonium 

 nitrate ; and further that if the mixture be more strongly heated, 

 nitrogen monoxide begins to be evolved at 230° and comes off 

 quite rapidly at 240° to 250°. A little ammonia is evolved how- 

 ever during the heating, the more ammonia being lost the longer 

 the mixture is kept between 220° and 230°. Consequently if at 

 the outset the mixture has been made in molecular proportions, 

 this evolution of ammonia leads to the setting free of some of the 

 higher nitrogen oxides towards the end of the reaction. To 

 remedy this the author increases the proportion of ammonium 

 sulphate ; and now the mixture having 5 per cent additional 

 sulphate, yields a larger quantity of nitrogen monoxide than 

 is obtained ordinarily from the equivalent quantity of ammonium 

 nitrate. The evolution of gas goes on more regularly than with 

 ammonium nitrate itself which at 240° is liable to decompose 

 with almost explosive violence.— J. Soc. Chem. Ind., xii, 10, 

 January 1893. G. f. b. 



3. On the Conversion of Yellow Phosphorus into the Red 

 variety. — When yellow phosphorus is crystallized from the ordi- 

 nary organic solvents of this substance, best by cooling a hot 

 solution of it, it is generally conceded that the crystals are 



Am. Jour. Sol— Third Series, Vol. XLVII, No. 282.— June, 1804. 

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