August i, 1895] 



NA TURE 



•40S : I 632 



The wave-kiigth of sound was determineil with this sample of 

 gas in a tube i metre in length and 9 mm. internal diameter ; 

 the vibrating rod was 580 mm. long. We found it exceedingly- 

 difficult to procure a tube in which really good sound*waves 

 could be shown with helium ; indeed, we were on several 

 occasions nearly despairing of gaining our object. But at last 

 perfect waves, easily read and easily counted, were produced, 

 and measurements were taken with the following results. 



Scries I. II. III. IV. V. VI. VII. 



"length ""/^^'^ 5^'^ 97-6 98-3 loo-o 986 979 mm. 

 Mean of all, 98 '8 mm. at iS'9°. 

 In air, a similar series gave the numbers 



Series ... I. II. III. IV. V. 



Half wave-length ... 36'00 3603 3611 3589 3616 

 Mean, 36'04 mm. at 20'I° 



The ratio of the specific heat at constant volume to that at 

 constant pressure for air is i 408 ; that for helium is — 



(36-04)'x( 273+i8-9)xi4-479 . (a8-Si=x-n8 

 273 + 201 



This sample of gas was again circulated over very hot magne- 

 sium and copper oxide for seven hours ; the magnesium had no 

 smell of ammonia when breathed on, nor did it turn red litmus 

 paper blue until after long standing. The magnesium was 

 mostly volatilised out of the hot part of the tube. 



The density of this sample of gas was determined. 



\'olume of bulb ... ... ... 162*843 c.c. 



Temperature.. ... ... ... 19S' 



Pressure (corr.) ... 7300mm. 



Weight 00278 gram 



Den.sity ... ... ... ... 2'I33 



The wavelength of sound was re-determined in the same tube 

 as before. The figures are 



Series... I. II. III. IV. V. VI. VII. VIII. 



Half \ 



wave- 1027 1007 1016 1007 I02'6 1016 1009 loi'i mm. 

 length. J 



Mean of all, 1015 mm. 



The ratio of the specific heats of helium, calculated from 

 the.se numbers as before, is I '652, a sufficiently close approxima- 

 tion to the theoretical number I 66. In the case of argon, the 

 purest specimen obtained gave for the ratio i'659: and as 

 remarked (in the Philosophical Transactions, 1895, 5-)> not 

 much dependence can be placed on the accuracy of the last 

 ligure. 



The result of these experiments goes to prove that the density 

 of the gas named helium is not less than 2'I3, and that it has 

 the same claim to be considered a monatomic gas as mercury 

 gas ; or if it is a mixture, it must be a mixture of monatomic 

 gases. 



As hydrogen was often evolved along with helium from 

 minerals, it occurred to us that if a definite ratio could be found 

 between the heliimi and the hydrogen evolved by the action of 

 acid, some idea might be gained a.s to the valency of helium. It 

 would be as if, for example, hydrogen and chlorine were evolved 

 separately from salt by .sulphuric acid, instead of in combination ; 

 by mea.suring each, the deduction could be drawn that chlorine 

 was univalent. Kxperiments made to this end showed, however, 

 that from some minerals no hydrogen is evolved. Cias, from a 

 sample of uraninile sent by Dr. Hillebrand, contained no trace 

 of hydrogen. It is, of course, possible, and, indeed, not unlikely, 

 that all hydrogen is absorbed in reducing the uranic oxide to 

 uranous oxide. The |irobIem then becomes a complicated one ; 

 but we hope to solve it by future experiments. 



As yet but few experiments have been made with the object of 

 inducing helium to enter into combination. Like argon, it is not 

 attacked by oxygen in presence of caustic stxla under the action 

 of the electric discharge ; indeed, this forms a good method of 

 removing all impurities other than argon. .Vgain, like argon, 

 it is not affected by red-hot magnesium, and it is not oxidised by 

 COp|x:r oxide at a red heat. 



As helium is evolved from cleveite and similar minerals at a 

 red heat, an attempt was made to reabsorb it by heating the 

 powdered mineral to redness in cimtacl with the gas, but not to 

 so high a temperature as that which had served to cause it to be 



NO. 



1344, VOL. 52] 



evolved. But the attempt was fruitless ; no gas was absorbed. 

 When all the gas in the tubes had t)een pum])ed out, after they 

 were cold, heating failed to cause the evolution of more gas. 



X further experiment was made, in which metallic uranium 

 was heated to bright redness with a blow-pipe in contact with a 

 mixture of helium and oxygen, the latter gas being greatly in 

 excess. But, curiously, the oxidation of the uranium was very 

 slow, and all the helium was recovered, none having been 

 absorbed. The conditions have yet to be discovered under 

 which helium can be made to combine with o.xides of uranium, 

 so as to reproduce the natural product. 



The Solitbilily of Helitim. 



Helium is verj' sixiringly soluble in water. A determination 

 made by the method previously described for argon {Phil. 

 Trans, h, 1895, 37) gave 00073 ^^ ''^ coefficient at l8'2^ 

 The tuf)e contained i62'3 arbitrary divisions, of which 26'0 

 were occupied liy helium and I36'3 by water. After shaking, 

 the volume of the helium was reduced to 25 'O dixisions, and 

 that of the water was increased to 137 '3. -As 1 37 '3 absorb 

 I o, I volume of water absorbs 00073 volume. The whole 

 apparatus was jacketed with running water during this experi- 

 ment. 



This is the lowest solubility hitherto recorded. Generally 

 speaking, the solubility of a gas is related to the temperature at 

 which it condenses to a liquid, and the sparing solubility of 

 helium points to its having a very low boiling point. Prof. 

 Olszew'ski has kindly undertaken to make experiments on the 

 temperature of liquefaction of helium, and it will be interesting 

 to find whether its boiling point does not lie below, or, at least, 

 as low as that of hydrogen ; for their molecular weights are not 

 very different, and helium is a monatomic gas, a condition which 

 appears to lower the boiling point. 



Helium is totally insolufjle in absolute alcohol and in benzene. 



The Spectrum of Helium. 



Mr. Crookes is making an exhaustive study of the siwctntm of 

 helium, and will shortly publish an account of his work. But, 

 as some of the deductions to be drawn later depend on the lines 

 observed, it is necessary' here to add a few words. In general 

 terms, the spectrum has already been described. The particular 

 point to which attention is neces.sary here is that at least two of 

 the lines in the spectnnn of helium, seen with a wide dispersion 

 prism, are coincident with two of the argon lines. These occur 

 in the red, and comprise one of each of the two pairs of 

 characteristic argon lines. This observation has been frequently 

 repeated, using for the purpose spectroscoiies of different dis- 

 persive jx)wer, and throwing into the field lx)ih spectra at the 

 same time, with an exceedingly narrow slit : and we may say 

 that if not absolutely identical, the lines are so near that it is not 

 possible with the means at our disposal to recognise any differ- 

 ence in position. But the relative brilliancy is by no means the 

 same. One of the argon lines, rather faint, is coincident with 

 the prominent red of the helium spectrum, .and one of the strong 

 red argon lines is coincident with a faint red line in the helium 

 spectrum. 



Besides the.se two, there is a liae in the orange-red, which 

 though perhaps not identical, yel9^ very clo.se. This line is 

 faint in helium, but moderately sm)ng in argon. It is much 

 more easily visible with helium in the " negative glow" than in 

 the capillary tulie. 



It may also f)e of interest to state that, according to Runge's ob- 

 .servation, the brilliant yellow line of helium is undoubtedly a 

 doublet. This was frequently observed by us with a grating of 

 14,000 lines to the inch in the spectrum of the third order. But it 

 must also be noted that one of the lines is very faint ; the other, 

 more refrangible, is immensely lirighter. The distance, judged by 

 eye, appears to be aliout l/50th part of that between the lines D, 

 and D, of sodium, .\ccurate information on this l.-ust point may 

 be looke<l for from Mr. Crookes, Mr. Lockyer, and from many 

 others who are interested in the probable occurrence of this 

 element in the sun.' 



III. General Conclusions, 



It cannot be dotdjted that a close analogy exists between 

 argon and helium. Both resist sparking with oxygen in 

 presence of caustic soda ; both are unattacked by red.-hot 

 magnesium ; and if we draw the usual inference from the ratio 



» Prof. Hale and Dr. Huggins have recently observed that the solar line 

 Dj is also a doublet. (\V. R., July 20)* 



