Manchester Memoirs, Vol. xliii. ( 1 899), No. 4. 15 



helium were distinctly visible. To the new gas we gave 

 the name " Neon," signifying " new " ; and our next 

 endeavour was to free it from the admixed helium. 

 Inasmuch as neither of these gases is liquefiable with the 

 means at our disposal, it was necessary to contrive a 

 method by which they could be separated from each 

 other. It was found in the solubility of both gases in 

 liquid oxygen. The mixture of gases was accordingly 

 mixed with enough oxygen to cause the whole to liquefy, 

 when exposed to the lowest temperature we could reach 

 with liquid air, boiling under low pressure ; and the 

 lightest fraction was, as before, collected separately. Its 

 spectrum showed the helium lines much more brilliantly 

 than before, and the residue less brilliantly. But it 

 showed, at the same time, the spectrum of argon. Hence 

 a new fractionation was attempted, in which the gas was 

 divided into three portions, the lowest-boiling of which 

 was still rich in helium ; the middle portion showed 

 helium and argon feebly, and neon brilliantly ; while the 

 last portion showed merely a trace of helium, but the 

 argon lines were fairly strong, among those of neon. Up 

 till now, we have not succeeded in preparing perfectly 

 pure neon, and we are still engaged in effecting a com- 

 plete separation. Let any organic chemist imagine that 

 he has to separate a mixture of pentane, hexane, and 

 octane from each other, by fractional distillation, and he 

 will realise the difficulties of the task. Still, there can be 

 no doubt that a fair separation has already been effected, 

 and the density of the purest specimen, I0"04, and iO'i9 

 in two experiments leaves little doubt of the final result ; 

 for it may be safely assumed that the higher density of 

 argon will balance to some extent the lower density of 

 helium, and that the true density of neon will not lie far 

 from lO'O. A determination of the ratio between the 



