Chemistry and Physics. 65 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Amounts of Neon and Helium in the Air. — Sir William 

 Ramsay, in connection with previous investigations, has roughly 

 estimated the amount of helium in the atmosphere at one or two 

 parts per million, and the amount of neon at one or two parts per 

 hundred thousand. He has now made more accurate determina- 

 tions of these constituents, and finds one volume of neon in about 

 81,000 volumes of air, or '00086 per cent by weight, and one 

 volume of helium in about 245,000 volumes of air, or -000056 per 

 cent by weight. (In the published article the percentages are 

 erroneously given as 100 times smaller than the above.) The 

 method used in these determinations was based upon the absorp- 

 tion of gases by charcoal as recently studied by Sir James Dewar. 

 The charcoal was kept at —100°, at which temperature neither 

 neon nor helium is absorbed in appreciable quantities, while the 

 other constituents may be almost completely absorbed by repeat- 

 ing the treatment. In this way about 2 CC of gas were left from 

 the treatment of 18 1. of air, and after the residual air had been 

 removed by sparking, the residue, which gave no spectrum of 

 argon, was measured in a delicate apparatus. The neon was then 

 condensed by charcoal at the temperature of liquid air in order 

 to separate it from helium as far as possible, and the separate 

 gases were afterwards measured. It appeared that this separa- 

 tion was a satisfactory one, although not absolute, and that the 

 helium determination may be somewhat too high. 



It is interesting to notice that Ramsay collected the lighter 

 gases from 540 cc of liquid air, corresponding to about 400 I. of 

 the gas, and that while he obtained a fair yield of neon and 

 helium, he could find no evidence of the presence of hydrogen in 

 this residue. The result appeared to show that there must be 

 less hydrogen in the air than 1/500 of the combined neon and 

 helium, but the author does not regard the experiment as quite 

 conclusive. — Chem. JVeivs, xci, 203. h. l. w. 



2. The Radio-activity of Thorium. — An account is given by 

 O, Sackue, of a product obtained by fractionating a mixture of 

 barium. and radium bromide obtained from 2*5 tons of thorianite. 

 It was found by Hahn that the more soluble fractions of this mix- 

 ture of bromides did not continually decrease in activity, as 

 would be expected from the removal of radium, but, after a series 

 of crystallizations, became more active. A strongly radio-active 

 product was obtained from this liquid by precipitation with 

 ammonia, and by solution in acid and precipitation with ammo- 

 nium oxalate the activity was still further concentrated. It was 

 found that the emanation from this substance lost one-half of its 

 activity in 52-55 seconds, and that it consequently corresponds 

 to the thorium emanation. This was confirmed by determining 



Am. Jour. Sci.— Fourth Series, Vol. XX, No. 115. — July, 1905. 

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