350 



NA TURE 



[February 7, 1895 



a mix'ure of 5 cc. of air with 7 c.c. of oxygfn was sparked for 

 Ij hours, ihe residue was o"47 c.c, and ader removal of oxygen 

 oxj6 c.c Several rcpetiiiiins having given similar result*, it 

 became clear that the final residue did not depend upon any- 

 thing that might happen when sparks passed through a greatly 

 reduced volume, /■«/ ■aias in {rofortion to the amount oj air 

 operat.J upon. 



No satisfactory examination of the residue which refused to 

 be oxidised could he made without the accumulation of a larger 

 quantity. This, however, was difficult of attainment at the time 

 in question. It was thought that the cause probahly lay in the 

 solubility of the gas in water, a suspicion since confirmed. At 

 leng'h, however, a sufficiency was cllecled to allow of spark- 

 ing in a specially constructed tu'-e, when a comparison with the 

 air spectium, taken under similar conditions, proved that, at 

 any rate, the gas was not nitrogen. .\t first scarcely a trace of 

 the principal nitrogen lines could be seen, but after standing 

 over water for an hour or two these lines became apparent. 



V. Early Expiiments on ll'it/idrawal of Nitrogen front Air ly 

 means of RcJIiot Afagnoiiim. 

 A preliminary experiment carried out by Mr. Percy Williams 

 on the absorption of atmospheric nitrogen, freed from oxygen 

 by means of red-hot copper, in which the gas was not passed 

 over, but simpiv allowed to remain in contact with the metal. 

 gave a residue of density I4"88. This result, although not con- 

 clusive, was encouraging ; and an attempt was made, on a 

 larger scale, by passing atmospheric nitrogen backwards and 

 forwards over redho! magnesium from one large gas-holder 

 to another to obtain a consideraKle quantiiy of the hcnvier gas. 

 In the course of ten days, about 1500 c.c. were collected and 

 transferred gradually to a mercury gas-holder, from which the 

 gas was passed over soda lime, phosphoric anhydride, mag- 

 nesium at a red-heat, copper oxide, soda-lime, and phosphoric 

 anhydride into a second mrrcury gas-holder. After some days 

 the gas was reduced in volume to ahoui 200 c.c, and iis density 

 was found to be l6-|. After further absorption, in which the 

 volume uas still further reduced, the density of the residue was 

 increased to iQ'og. 



On passing sparks for several hours through a mixture of a 

 small quantity of this gas with oxygen, its volume was still 

 further reduced. Assuming that this reduction w.is due to the 

 further elimination of nitrogen, the density of the remaining 

 gas was calculated to be 200. 



The spectrum of the gas of density 1909, though showing 

 nitrogen bands, showed many othrr lines wbich were not recog- 

 ■isable as belonging to any known element. 



VI. Proof of the Presence of Argon in Air by means of 

 Atmolysis. 



It has already (§ II.) been suggested that if "atmospheric 

 nitrogen" contains two gases of different densities, it should 

 lie possible to obtain direct evidence of the fact by the 

 method of atmolysis. The present section contains an account 

 of carefully conducted experimen's directed to this end. 



The atmilyser was prepared (after (Jrnham by combining a 

 number of "churchwarden" tobacco pipes. At first twelve 

 pipes were used in three group', each group including four 

 pipes conneced iu scries. The three groups were then con- 

 nected in parallel, and placed in a large glass tube closed in 

 such a way that a partial vacuum could be maintained in Ihe 

 space outside the pipes by a water pump. One end of the 

 combination of pipes was open to the atmosphere ; the other 

 end was connected to a boitle aspirator, initially full of water, 

 and so arranged as to draw about 2 per cent, of the air which 

 entered the other end of the pipes. The gas collected was 

 thus a vety small proponiun of ihal which leaked through the 

 pores of the pipes, and should be ri-laiively rich in the heavier 

 constituents of the atmosphere. The flow of water from the 

 aspirator could not be maiiaiined very constant, but the rate of 

 2 per cent, was never much exceeded. 



The air thu« obtained was treated exactly as ordinary air had 

 been trealeil in determinations of the density of atmospheric 

 nitrogen. 0<)gen was removed by red hot copper, followed 

 by cupric oxide, ammonia by sulphuric .icid, moisture and car- 

 bonic acid by po'aih and phosphoric anhydride. 



In a total weight of approximately 23 grams the excess of 

 weight of the diffused nitrogen over oniina'y atmospheric nilro- 

 jjen was in four experimei t<, 00049. 00014, 00027, 00015. 



The mean exce»s of the lour dcicrminations is 0'00262 gram, 



NO. 1319, VOL. 51] 



I 

 or, if we omit the first, which depended upon a vacuum weighs 

 ing of two months old, 0001S7 gram. 



The gas from prepared air was thus in every case denser than 

 from unprepared air, and to an extent much beyond the possible 

 errors of experiment. The excess was, however, less th.in had 

 been expected, and it was thought that the arrangement of the 

 pipes could he improved. The final delivery of gas fiom each 

 o.' the gioups in larallel being so small in compaiison with the 

 whole streams concerned, it seemed possible that each group 

 was not contributing its proper share, and even ihat there might 

 be a flow in the wrong direction at the delivery end of one or 

 two of them. To meet this objection, the arrangement in 

 parallel had to be abandoned, and for the remaining experi- 

 ments eight pipes were connected in simple series. The porous 

 surface in operation was thus reduced, but this was p.irtly com- 

 pensated for by an improved vacuum. Two experiments were 

 made under the new conditions, in which the excess was 

 I., 00037 ; II., o'oo33. 



The excess being larger than before is doubtless due to the- 

 greattr efficiency of the atmolysing apparatus. It should be 

 mentioned that the above recorded experiments include all that 

 have been tried, and the conclusion seems inevii.ible that 

 "atmospheric nitrogen" is a mixture, and not a simple body. 



It was hoped that the concentration of the heaviei constituent 

 would be sufficient to facilitate its preparation in a pure state by 

 the use of prepared air in substitution for ordiimy air in the 

 oxygen apparatus. The advance of 3! milligrams on the II 

 milligrams, by which atmospheric niirogen is heavier than 

 chemical nitrogen, is indeed not to be despised, and the use of 

 prepared air would be convenient if the diffusiim apparatus 

 could be set up on a large scale and bs made thoroughly self- 

 acting. 



VII. Negative Experiments to firoTe t/'ial Argon is not JeriveiC 

 from Nitrogen from Chemical Sources. 



.\Ithough the evidence of the existence of argon in the atmo- 

 sphere, deiived from ihe comparison of densities of atmospheric 

 and chimical nitrogen and from the ditTusion experiments 

 (§ VI.), appeared ovcr» helming, we have thought it undesirable 

 to shrink from any labour that would tend to complete the 

 verification. Wiih this object in view, an experiment was 

 undertaken and carried to a Conclusion on N'ovemher 13, in 

 which 3 litres of chemical nitrogen, prepared from ammonium 

 nitrite, were treated wiih oxygen in precisely the manner in 

 which atmospheric nitrogen had been found to yiclil a residue 

 of argon. The gas remaining at the close of the large scale 

 opeiations was worked up as usual with batteiy and coil until 

 the spectrum showed only slight traces of the niirogen lines. 

 When cold, the residue measured 4 c.c. This was transferred, 

 and after treatment with alkaline pyrogallalc to remove oxygen, 

 measured 33 c c. If atmospheric nitrogen had been employed, 

 the final residue should have been about 30 c.c. Of the 3'3c.c. 

 .ictually left, a part is account! d lir by an acciileni, and the 

 result of the cxpcrimi nt is to show that argon is not formed by 

 sparking a mixture of oxygen and chemical niirogen. 



In a second ixpenmini of thesamc kind 5660 c.c. of nitrogen 

 from ammonium nitrite was treated with ox)gcn. The final 

 residue was 35 c.c. and was found to consist mainly of argon. 



The source of the residual aigon i^ to be sought in the water 

 used for the manipulation of the large quantities of gas (1 litres 

 of nitrogen and II litresof oxygen) employed. When carbonic 

 acid was collected in a similar manner and subsequently ab- 

 sorhuil by potash, it was fiund to have acquired n contaiuinalion 

 consistent with this explanation. 



Negative experiments were also carried out, absorbing nitro- 

 gen by means o( magnesium. In one instance 3 litres of nitrogen 

 prepared from ammonium chloride an<l bleaching-powder was 

 reduced in volume to 45 c. c , and on sjiarking with oxygen its 

 volume was further reduced to about 3 c.c. The residue ap- 

 peared lo consist of argon. Another cxpctimmt, in which 15 

 litres of nitrogen from ammonium nitiite was absorbed, gave a 

 final residue o( 35 c.c. Atmospheric nitrogen, in the latter 

 ca.se, would have yirlded 150 c.c, hence less than ^„\\\ of the 

 noimal ({uantity was obtained. It should be mentioned that 

 leakage occurred at <ine stage, by which perhaps 200 c.c of air 

 entered the apparatus ; and liesides, the nitrogen was collected 

 over water from which it tloublless acquired .some argon, 

 tjuantitative negative experiments of this nauiie are exceedingly 

 diflicull, and require a long lime to cany them 10 a successful 

 conclusion. 



I 



