348 



NA TURE 



[February 7, 1895 



degree obviated hy passing the gas over hot metals. For the 

 filliops of tune 6. 9, and 13 ihe ga* pas-ed ihroi'gh a ^ho^t 

 leag'h of I u^e containing coi>pei"in the lorm of fine "ire hraied 

 by a flat Bun'en burner, then through ihe fomace over red hot 

 iron, and batk over copper oxide. On Jure 19 the furnace 

 tubes were omitted, the gas being trealert with red hnt copper 

 only. The mean result, reduced so as to correspond with those 

 above quoted, is 2 29S5. 



Without u.'.ing heat, it has not been found possible to prevent 

 the corrosion (■! the mercur)'. Kven whtn no una is employed, 

 and air simply bubbled through, the hypoliromiie siduiion is 

 allowed 10 pass with constant shaking over mercury contained 

 in a y lute, ihe surface of the meial «a«soon fouled. 



Although the results relating to urea nilrogen are interesting 

 for compaii-on with that obtained from other nitrogen com- 

 pounds, the original object was not attained on account of the 

 necessiiy of reaming the treatment with hot me'als. \Ve have 

 found, however, ihit nitrogen from ammonium nitrite may be 

 prepared without the employment of hot tules whose wcijjht 

 agrees wiih that above quoted. It is true that the gas smells 

 slightly of ammonia, easily removable by sulphuric acid, and 

 apparently also of oxides of nitrogen. The mean lesull from 

 three fil ings is 2 29S7. 



It will l)e seen that, in spite of the slight nitrous smell, there 

 is no appreciable difference in ihe densities of gas prepared 

 from ammonium nitrite with and without the treatment by hot 

 metals. The result is interesting as showing that the agree- 

 ment of numbers obtained for chemic.il nitrogen does not 

 depend upon the use of a red heat in the process of puri6ca- 

 tion. 



The five results obtained in more or less distinct ways for 

 chemicil nitrogen stand thus : — 



From nitric o»ide 2"300I 



From nitrous oxide ... ... ... ... 2'2990 



From am nonium nitrite purified at a red heat 22987 

 From urea ... ... ... ... ... 2 2985 



From ammonium nitrite purified in the cold 2 2987 



Mean ... ... ... 2*2990 



These numbers, as well as those above quoted for "atmo- 

 spheric nitrogen, " are subject to a deduction o( o 0006 for the 

 shrinkage of the globe when exhaus'ed.' If they are then 

 multiplied in the ratio of 2 310S : I 2572, ihey will express the 

 weights of the gas in grams per litre. Thus, as regards Ihe 

 mean numbers, we find ts the weight per litre under standard 

 conditions of chemical nitrogen 1 '2505, that of atmospheiic 

 nitrogen being I 2572. 



It i-. of interest to compare the density of nitrogen obtained 

 from chemical compoumis with that of oxygen. We have 

 N, : O, = 2*2984 : 26276 = o 87471 ; so that if 0„ = 16, 

 Mj = ■3'9954. Thus, when the comparison is with chemical 

 nitrogen, the ratio is very nearly that of 16 : 14 ; but if " atmo- 

 spheric nitrogen" be substituted, the ratio of small integers is 

 widely departed from. 



To the above list may he added nitrogen prepared in yet an- 

 other manner, who«e weight has been determined sub-trqucnily 

 to the isolation of the new dense constituent of the atmosphere. 

 In this case nitrogen was actually extracted from air by means 

 of magnesium. The niirogen thus srparated was then con- 

 verted into ammonia by action of water up in the magnesium 

 nitride, ami aft'-rwards liberated in the free stale by means of 

 cilcrum hy|>ochlorilc. The purification was conducted in the 

 usual way, and included passige over red hot copper and copper 

 oxide. The following was the result : — 



Globe empty, October 30, November 5 ... 2 823 13 

 Globe lull, October 31 o'Si395 



Weight of gas . ... ... 229918 



It difffrs inappreciably from the mean of other results, viz. 

 3°a990, and i> of special interest as relating to gas which at one 

 •tage of its history formed part of the atmosphere. 



Another determination, with a different apparatus, of Ihe 

 density of "chemical" nitrogen from the same source, mag- 

 neiium nitride, which had been prepared by passing "atmo- 

 spheric" nitrogen over ignited magt.e^ium, may here be 

 recorded. The sample differed f'om that prcviowly mentioned, 

 inasmuch as it had not been subjected to treatment with red- 



' Raylrigh, " On ihe Dcntitiei of the Principal Cuct," Roy. Soc. free. 

 %o). liti. p. Ill, rR)). 



NO. I3I9, VOL. 51] 



hot copper. After treating the nitride with water, the resulting 

 ammonia was distilled off, and collected in hydmchloric acid; 

 the solution was evaporated by dei.rc-es, the dry ammonium 

 chloride was dissolved in water, and its conon rated ."olutioB 

 added to a freshly- prepared solutim of so ium hypobiomite. 

 The nitr-'gen was collected in a gasholder over water which 

 had previou-ly been boilet, so as, at all events, partially to 

 expel air. The nitrogen passed into the vacuous gl .1 e through 

 a solution of potassium hydn xi ie, and through two dr\ing- 

 tubes, one containing soda-lime, and the otticr phosphoric 

 anhydride. 



At 1838° C. and 754 '4 mm. pressure, 162 S43 c.c. of this 

 nitrogen weighed 0*18963 gram. Ilf-nce, 



Weight of I litre at o" C and 760 mm. pressure = I •2521 

 gram. 



'Ihe mean result of the weight of i li're of "chemical" 

 nitrogen has been found to equal I 2505. It is therefore 

 seen that "chemical" nitrogen, derived noin " atmospheric" 

 nitrogen, without any exposure to red hot copper, possesses the 

 usual densi y. 



Experiments were also made, which had for their object to 

 prove that the ammonia produced (rom the magresium liitride 

 is identical with ordinary ammonia, and contains no other com- 

 pound of a basic character. For this purpose the ammonia 

 was converted into amminiiim chloride, and the percentage of 

 chl->rine determined by tiira'ion with a solution of silver nitrate 

 which had been standardised by limiting a specimen of pure 

 sublimed ammonium chloride. The silver solution was of such 

 a strength that I c.c. precipitated the cliloiine from 0001701 

 gram of ammonium chloride. 



(1) Ammonium ch oride from orange-coloured .sample of 

 magnesium nitride contained 66 35 per cent, ot chlorine. 



(2) Ammonium chloride from bl.icki»h magnesium nitride 

 contained 66 35 per cent, of chlorine. 



(3) Ammonium chloride from nitride containing a large 

 amount of unaltackcd magnesium contained 66 '30 per cent, of 

 chlorine. 



Taking for the atomic weii;hls of hidrogen II = i"oo32, of 

 nitrogen N = 1404, and of chlorine CI = 35 46, the theo- 

 retical amount of chlorine in ammonium chluiidc is66'27 per 

 cent. 



From these results — !hat niirogen prepared from magnesium 

 nitride, obt.tined by passing "atmospheric" niirogen over ted- 

 hot magnesium has the density of "chemical " nitrogen, and 

 that ammonium chloride, prepared (rom magnesium nitride, 

 contains practically the same percentage of chlorine as pure 

 ammonium chloride — it may be c<mcluded that red-hot mag- 

 nesium with^lraws Irom "atmospheric nitrogen" no substance 

 other than nitrogen capable of forming a basic compound with 

 hydrogen. 



II. Reasotis for susfeeting a hitherto Undiscovered Con- 

 stituent in Atr. 



When the discrepancy of weights was first encountered, 

 attempts were naturally made to explain it by contamination 

 wiih known impurities. Of these the in 1st liki^ly appeared to be 

 hydrogen, present in the lighter cas in spite of the p.tssage over 

 red-hot cupric oxide. Hut inasmuch .is the intentional introduc- 

 tion of hydrogen into the hcivi r i;as, nfter>vatds treated in Ihe 

 same w.iy with cupric oxide, ha 1 no ■ ffect upon its weight, this 

 explanation had to be abandoned, and finally it became clear 

 that the dilT. rcncc could not be accounted lor by the presence 

 of anv known impurity. At this stage it seemed not improb- 

 able that the lightness of the gas extracted from chemical 

 compounds was to be explained by partial dissociation of 

 nirogrn molecules N. into detachcii atoms. In order to test 

 this suggestion both kimls of gas were submitleil to the action 

 of the silent electric discharge-, with the result that boih retained 

 their weights un.-iltered. This was discouraging, and a lurthcr 

 experiment pointed still more markedly in the negative direc- 

 lion. The chemical behaviour of nitrogen is such as to suggest 

 that ilissocialcd atoms would possess a high degree of .ictivity, 

 and that even though tliey might be formci in the first instance 

 their lilc would probably be short. On sianding iliey might be 

 exprc cil to ilisappear, in partial analogy wiih the known 

 liehivioiir of ozone. With this idea in view, a sample of 

 chemically prepared nitrogen was stored lor eight months. But 

 al the end of this time the dci.sity showed no sign of increase, 

 remaining exactly as at first.' 



' Key. Stc. Prjc. vol. Iv., p. 344, iB<t4. 



