164 



NATURE 



[December 13, 1900 



"The Heavens at a Glance," 1901.— This handy 

 little publication (now in its fifth year of issue) is practically 

 a card calendar devoted to astronomical particulars, and is 

 designed to serve as a handy remembrancer as to the phenomena 

 * predicted for any period, any further details required being 

 obtained from a more bulky volume of reference. Besides the 

 daily phenom ena of importance, monthly summaries of the 

 aspects of constellations, sun's declination, moon's phases, and 

 positions of planets are given. This occupies about half of the 

 sheet. The remainder is devoted to a series of useful descrip- 

 tive notes and statistics of various celestial objects, including 

 special features on the moon's terminator during the lunation, 

 elongations and oppositions of the planets, data for eclipses, 

 meteor shower radiants, and the coordinates of a selection of 

 the brightest stars. This card should be especially useful to 

 amateurs who find the larger reference books too cumbersome. 

 It may be obtained from the compiler, Mr. Arthur Mee, 

 F. R.A.S., Tremynfa, Llanishen, near Cardiff. 



"Companion to the Observatory" for 1901. — This 

 useful contribution to the astronomer's library has recently been 

 issued, and will doubtless be accorded its usual welcome. The 

 contents, occupying 36 pages, have from experience been so 

 condensed as to leave out no information likely to be wanted 

 by the general worker that little or no alteration has been 

 made in the arrangement. Beginning with particulars of the 

 sun's times of rising, setting, its declination, mean and sidereal 

 time, and phases of the moon for every week, there follows a 

 calendar showing the times of rising, southing and setting of 

 the moon, and the longitude of the terminator for each day of 

 the year ; a list of the principal radiant points of meteors, com- 

 piled by Mr. Denning ; ephemerides for all the planets, 

 including the minor planets Ceres, Pallas and Vesta ; and 

 times of elongation, stationary points, &c. ; solar and lunar 

 eclipses, occupations ; phenomena of the satellites of Mars, 

 Jupiter, Saturn, Uranus and Neptune ; ephemeris containing 

 data for physical observations of the sun ; mean places of 

 variable stars, with epochs of maxima and minima ; particulars 

 of 115 double stars. 



ARGON AND ITS COMPANIONS} 



'T*HE discovery of krypton and neon was announced to the 

 Royal Society in the early summer of 1898 ; and subse- 

 quently atmospheric air was found to contain a heavier gas to 

 which the name of xenon was applied. Mr. Baly, in the autumn 

 of the same year, called attention to the presence of helium 

 lines in the spectrum of neon, an observation which confirms 

 that made by Prof. Kayser, of Bonn, and by Dr. Friedlander, 

 of Berlin. 



At the same time we imagined that we had obtained a gas with 

 a spectrum differing from that of argon and yet of approximately 

 the same density ; to this gas we gave the name metargon. It 

 has now been found that the presence of the so-called metargon 

 is to be accounted for by the fact that in removing oxygen from 

 the mixture of these gases, which was' then in our hands, 

 phosphorus containing carbon was employed ; this mixture 

 when burned in oxygen yields a spectrum to some extent 

 identical with that furnished by carbon monoxide, but differing 

 from it inasmuch as lines of cyanogen are also present. We 

 have no doubt that the so-called metargon, the spectrum of 

 which is visible only at high pressure, and only when impure 

 phosphorus has been employed to remove oxygen, must be 

 attributed to some carbon compound. In spite of numerous 

 experiments we have not yet succeeded in producing any gas in 

 quantity which yields this composite spectrum. It is only to be 

 obtained by a mixture of carbon monoxide with cyanogen. 



To obtain the heavier gases krypton and xenon, a large 

 amount of air was allowed to evaporate quietly ; the residue 

 was freed from oxygen and nitrogen, and then consisted of a 

 mixture of krypton, xenon and argon, the last forming by far 

 the largest portion of the gas ; this mixture was liquefied by 

 causing it to flow into a bulb immersed in liquid air, and the 

 bulk of the argon was removed as soon as the temperature rose, 

 the krypton and the xenon being left behind. By many 

 repetitions of this process we were finally successful in separating 

 these three gases from each other. While krypton has a 

 considerable vapour-pressure at the temperature of boiling air, 



1 A paper by Prof. William Ramsay, F.R.S., and Dr. Morris W. 

 Travers. Read at the Royal Society on November 15. 



NO. 1624, VOL. 63] 



the vapour-pressure of xenon is hardly appreciable, and this 

 afforded a means of finally separating these two gases from one 

 another ; in the complete paper the operations necessary to 

 separate them are fully described. 



For neon the process of preparation was different. The air 

 liquefier furnished a supply of liquid air ; the gas escaping from 

 the liquefier consisted largely of nitrogen ; this mixture was 

 liquefied in a bulb immersed in the liquid air which the machine 

 was making. When the bulb had been filled with liquid 

 nitrogen a current of air was blown through the liquid until some 

 of the gas had evaporated. That gas was collected separately, 

 and deprived of oxygen by passage over red-hot copper ; it 

 contained the main portion of the neon and the helium present 

 in the air. The remainder of the nitrogen was added to the 

 liquid air used for cooling the bulb in which the nitrogen was 

 condensed. Having obtained a considerable quantity of this 

 light nitrogen it was purified from that gas in the usual manner, 

 and the argon containing helium and neon was liquefied. By 

 fractional distillation it was possible to remove the greater 

 portion of the helium and neon from this mixture of gases, 

 leaving the argon behind. Many attempts were made to 

 separate the helium from the neon. Among these was 

 fractional solution in oxygen, followed by a systematic diffusion 

 of the two gases ; but it was not found possible to raise the 

 density of the neon beyond the number 9 '16, and its spectrum 

 still showed helium lines. It was not until liquid hydrogen, made 

 by an apparatus designed and built by one of us (M. W, T.), 

 had been produced in quantity, that the separation was effected %. 

 the neon was liquefied or perhaps solidified at a temperature of 

 boiling (hydrogen, while the helium remained gaseous. A few 

 fractionations serve to produce pure neon ; we did not attempt 

 to separate the helium in a pure state from this mixture. 



That these are all monatomic gases was proved by determina- 

 tion of the ratio of their specific heats by Kundt's method ; the 

 physical properties which we have determined are the refrac- 

 tivities, the densities and the compressibilities at two tempera- 

 tures, and of argon, krypton and xenon the vapour-pressures 

 and the volumes of the liquids at their boiling points. 



The results are as follows : — 



The compressibilities of these gases also show interesting 

 features. They were measured at two temperatures — 11-2° and 

 237-3'' J the value of P.V. for an ideal and perfect gas at 11-2'^ 

 is 17,710 metre-cubic-centimetres, and at 237-3° to 31,800. This 

 is, of course, on the assumption that the product remains 

 constant whatever be the variation in pressure. Now with 

 hydrogen at 11 '2° C. the product increases with the rise of 

 pressure ; with nitrogen, according to Amagat, it first decreases 

 slightly and then increases slightly. With helium the increase 

 is more rapid than with hydrogen ; with argon there is first a 

 considerable decrease followed at very high pressures by a 

 gentle increase, although the product does not reach the 

 theoretical value at 100 atmospheres pressure ; with krypton 

 the change with rise of pressure is a still more marked decrease, 

 and with xenon the decrease is very sudden. At the higher 



