352 



NATURE 



[February 7, 1895' 



green lines occurs orxt, besides a number of less intensity. Of 

 the group of five, the second, which is perhaps the most bril- 

 liant, has the wave-length 56100. There is next a blue or 

 blue violet line of wave-length 4702 ; and last, in the less easily 

 visible part of the spectrum, there are five strong violet lines, of 

 which the fourth, which is the most brilliant, has the wave- 

 length of 420'0. 



Unfortunately, the red lines, which are not to be mistaken 

 for those of any othtr suhstancc, are not easily seen when a 

 jar discharge is passed through argon at atmospheric pressure. 

 The spectrum seen under these -conditions has been examined 

 by Prof. SchuNier. The most characteristic lines are perhaps 

 those in the neighbourhood of 1-", and are very easily seen if 

 there be not too much nitrogen, in spite of the presence of 

 some oxygen and water vapour. The approximate wave- 

 lengths are — 



blrong. 



F. 



Not quite so strong. 



Strong. 



Fairly strong charac- 

 teristic triplet. 



4S7 91 

 [48607]... 



4S4 7> - 

 480 52 .. 

 476-50 ... 



473 5^ - 

 472 56 ... 



It is necessary to anticipate Mr. Crookes' communication, 

 and to stale that when the current is passed from the induction 

 coil in one direction, that end of the capillary tube next the 

 positive pole appears of a redder, and that next the negative 

 pole of a bluer hue. There are, in effect, two spectra, which 

 Mr. Crookes h.is succeeded in separating to a considerable 

 extent. Mr. E. C. Baly, who has noticed a similar 

 phenomenon,' attributes it to the presence of two ga.ses. The 

 conclu-inn would fdUow that what we have termed "argon" 

 is in reality a mix'ure of two gases which have as yet not been 

 separated. This conclusion, if true, is of great importance, and 

 experiments are now in progress to test it by the use of other 

 physical methods. Ihe full bearing of this possibility will 

 appear latrr. 



The presence of a small quantity of nitrogen interferes 

 greatly wi'h the argon spectrum. But we have found that in a 

 tube «ih platinum ekclrodcs, after the discharge has been 

 passed fir f lur hours, the spectrum of ni'rogen disappears, and 

 the argon spectrum manifests ilself in full purity. A specially 

 constructed tube wiih magnesium electrodes, which we hoped 

 would yield good results, removed all traces of nitrogen, it is 

 true; but hydrogen was evolved from the magnesium, and 

 showed its characierisiic bnes very strongly. However, these 

 are easily identified The gas evolved on heating magnesium 

 in vacuo, as proved by a separate experiment, consists entirely 

 of hydrogen. 



Mr. Cro'ikes has proved Ihe identity of the chief lines of the 

 spectrum of gas separated from air-nilrogen by aid of magnesium 

 with that remaii'ing after sparking the air-nitrogen with oxygen 

 in presence of caustic soda solution. 



I'rof. .Schust r also has found the principal lines identical in 

 the spectra of the two gases, as observed by the jar discharge 

 at atmospheric pressure. 



XII. Solubility of Argon in H'a'.cr. 



Uelerminaiions of the solubility in water of argon, prepared 

 by sparking, gave 3 94 volumes per too of water at 12'. The 

 solubility of gi« prepared by means of magnesium was found to 

 be 4*05 vidumes per 100 at ijg". The gas is therefore about 

 2^ liiuct as solul>le as iiiiri>gcn, and possesses approximately 

 (be same s>ilu>>ility as oxygen. 



The fact that argon is more soluble than nitrogen would lead 

 us to expect it in increa-ed proportion in the dissolved gases of 

 rain naier, Experiment ha< confirmed this anticipation. 

 "Nitiogrn" prepircd frrim the dissolved gases of water 

 supplied fiom a r.iin-water cislern w.is wei^^hed upon two 

 occasions. The wci,;hi«, corresponding to those recorded in 

 ( I- , were 2'322I and 2 3227, showing an excess of 24 milligrams 

 above the weight of t>ue nitrogen. .Since ihe corresponding 

 excess (or " atmospheric nitrogen " is 11 inilligiam<, we con- 

 clude thai ihc water " nitrogen " is relatively more than twice 

 as rich in argon. 



On the other band, gas evolved from Ihe hot spring at Bath, 



• rri>i. f'liyt S»c-, i8>3, p. 147. He Myt :— " When an electric current 

 tk pa«««d thr u4^ ■ •i4iiiire of iwotaMff, one it tc|mratcd from itic other 

 and a^pcariin ilie negative hIow." 



NO. 1319. VOL. 51] 



and collected for us by Dr. A. Richardson, gave a residue afler 

 removal of oxygen and carbonic acid, whose weight was only 

 about midway between that of true and atmospheric nitrogen. 



XIII. Behaviour at Loiv Temperatures.^ 



Prelimin.ary experiments, carried out to liquefy argon at a 

 pressure of about too atmospheres, and at a temperature of 

 — 90', failed. No appearance of liquefaction could be observed. 



Prof. Charles Olszewski, of Cracow, the well-known authority 

 on the constants of liquefied gases at low temperatures, kindly 

 offered to make experiments on the liquefaction of argon. His 

 results are embodied in a sepitaie cominunication, but it is 

 allowable to stale here that the gas has a lower critical tempera- 

 lure ( - 121°) and a lower boilirg point t - 187°) than oxygen, 

 and that he has succeeded in solidifying argon to white crystals, 

 melting at -l89'6". The density of the liquid is approxi- 

 mately 1*5, that of oxygen being 1124, and of nitrogen 0SS5. 

 The sample of gas he experimented with was exceptionally 

 pure, and had been prepared by help of magnesium. It showed 

 no tiace of nitrogen when examined in a vacuum tube. 



XIV. Ratio of Specific Heats. 



In order to decide regarding the elementary or compound 

 nature of argon, experiments were made on the velocity of 

 sound in it. It will be lemeuibered that, from the velocity of 

 sound in a gas, the latio of specific he.it at constant pressure to 

 that at constant volume can be deduced by me.ius of the 

 equation 



when « is the frequency, .\ the wavelength of sound, v its 

 velocity, e the isothermal ol.isticily, li the density, (i -k- at) the 

 temperature correction, C,, the specific heal at constant pres- 

 sure, and C, that at constant volume. In comp.aring two gases 

 at the same temperatuie, each of which obeys Boyle's law with 

 sufficient approximation, and in using the same sound, many of 

 these ttrms disappear, and the ratio of specific heats of one gas 

 may be deduced from that of the other, if known, by means of 

 the proportion 



K-d : K''-d' :: I 41 : x, 



where, for example, A. and d refer to air, <.f which the ratio is 

 l'4i, according to observations by Riintgen, WUIlner, Kayser, 

 and Jamin and Richard. 



Two completely different series of observations, one in a tube 

 of about 2 mm. diameter, and one in one of 8 mm., made with 

 entirely dilTerent samples of gas, gave, the first, I 65 as the 

 ratio, and, the second, I 61. 



Experiments made with the first tube, to test the accuracy of 

 its working, gave for caibon dioxide the ratio 1276, instead of 

 I '288, the mean of all jirevious deter inin.ations ; and the half 

 wave-length of sound in hydrogen w-ts fouml to be 736, 

 insiead of 74 5, the mean of those previously found. The ratio 

 of the specific heats of hydrogen found was i ' j9, instead of 

 I -402. 



There can be no doubt, therefore, that argon gives practi- 



cal'y the ratio of specific heats, viz. i 66, proper to a gas in 



which all the energy is translalional. The only other gas 



which has been found to behave similarly is mercury gas, at a 



I high temperature. 



' -W. .Atlcmfts to induce Chemical Ccmliiiuition. 



Many atlcmpls to induce argon to combine will be described 

 in fiill in ihe complete paper. Suffice it to say here, that all- 

 suih attempts have as yet proved abortive. Argon does not 

 combine with oxygen in presence of alkali under the influence 

 of the electric di^chargc, nor with hydrogen in picseiice of aciti 

 or alkali also when sparked ; nor with chlorine, diy or moist, 

 when sparked ; nor with phosphorus at a bright-red heat, nor 

 with sulphur at bright redness. Tellurium maybe distilled ip 

 a current of the gas; so may sodium and ]o:assium, their 

 metallic lustre remaining unchanged. It is unabsorbed 

 by passing it over fused red hot caustic soda, or sidn-lime 

 healed to bright redness ; it passes unaffected over fused and 

 bright icd-hot potassium nilrale; and red-hot sodium peroxide 

 does not combine with it. Persulphidcs of sodium and calcium 



1 The arraneemcnts for the expnimcnts upon ihis branch of the subject 

 were left cnlircty in ('rof. Rams y\ hnnds. 



' Kundland Warburg, l'«es I"", vol. cxxxv, pp. Jj; and 507. 



