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Prof. W. Ramsay. Helium, a Gaseous [Mar. 19, 



infinitesimal. This was easily ascertained from experiments made 

 on the spectra of mixtures of gases by Dr. Collie and myself. 

 About 01 per cent, of nitrogen is still visible ; and the higher 

 the pressure the more easily is the spectrum of nitrogen seen when 

 it is mixed with helium. With these new samples of gas, the 

 nitrogen spectrum was just visible at a pressure of 4 or 5 mm. ; 

 and that implies that only the minutest trace can have been present. 

 It doubtless comes off the glass tubes in which the powdered minerals 

 were heated, or it may have adhered to the surface of the powdered 

 mineral. I think it may be safely assumed that nitrogen is not a 

 normal constituent of these minerals. There was always a consider- 

 able amount of carbon dioxide evolved, and, as the carbon spectrum 

 persisted even after the gas had been passed through soda-lime, 

 probably a hydrocarbon, but this only in minute amount. 



§ 2. The yield from these sources was very variable. Whereas 

 1 gram of cleveite yielded 7*2 c.c. of helium, 1 gram of broggerite 

 yielded somewhat less than 1 c.c. of helium ; the yield from samarskite 

 was still less, about 6 c.c. per gram ; and from fergusonite 1*1 c.c. 

 per gram, the last by heating alone ; with the other minerals, the 

 residue after heating was fused with hydrogen potassium sulphate. 

 There can be no doubt that cleveite is far the best source of the gas, 

 but unfortunately it is very scarce. 



§ 3. Dr. Collie, to whom I owe thanks for helping to extract these 

 gases, was so good as to analyse the gas obtained from fergusonite on 

 heating. It contained 



Hydrogen 54*7 per cent. 



Carbon dioxide 13*9 „ 



Helium 31-2 



99-8 „ 



No hydrocarbons were present, for, after explosion with oxygen, no 

 contraction occurred on admitting potash ; the residue gave a spectrum 

 free from nitrogen flutings even when the pressure was compara- 

 tively high. 



The carbon dioxide was absorbed by soda-lime, and the remaining 

 mixture was then circulated over the usual purifiers — red-hot copper 

 oxide, soda-lime, phosphoric anhydride, and red-hot magnesium. 

 Although no nitrogen was present, magnesium was introduced as a 

 precautionary measure. 



§ 4. The density of the gas extracted from broggerite was first 

 determined. The precautions taken and the methods of weighing 

 were similar to those described in the paper on argon, in the ' Phil. 

 Trans.' for 1895. The bolb, of capacity 162'843 c.c, was counter- 

 poised by one nearly equal to it in volume and weight, and the 



