2 14 



NA rURE 



\_yune 27, 1889 



with those of oxygen and capable of taking up vibrations of the 

 sanie period. At least we must conclude that little, if any, of 

 the oxygen of these and other compounds is ever out of the 

 influence of the other components. 



The authors have re-examined the absorption-spectrum of N.JO4 

 at various temperatures, and agree with the conclusions of Bell 

 {Amer. Chcm. Journ., vol. vii. ]). 32), that N2O4, whether liquid 

 ■or gaseous, effects only a general absorption at either end of the 

 •spectrum, and that the selective absorptions observed with it are 

 due to the presence of NO2. 



In order to obtain pure ^Si^, the tube in which the liquid was 

 ■sealed was placed in a freezing mixture, and a large part of the 

 liquid frozen ; the remaining liquid was then drained as com- 

 pletely as possible into the other end of the tube, and sealed off. 

 It should be observed that the crystals of N2O4 appear colour- 

 less, and that when they are melted the liquid and superincumbent 

 -vapour are of a very pale yellow colour. As the temperature rises, 

 both liquid and vapour become, as is well known, of a deep 

 orange, and finally of a dark, reddish-brown colour. The authors 

 -examined the spectra produced by two thicknesses of liquid and 

 vapour — (i) by that contained in a narrow tube about i mm. in 

 <liameter, and (2) by that in a tube about i cm. in diameter. 

 At 15° to 20° the vapour in the narrow as well as in the wider 

 tube showed the well-known absorption-spectrum of fine, dark 

 lines ; no absorption by the liquid in the narrow tube could be 

 detected, and the liquid in the wide tube showed no fine lines, 

 but several faint, very diffuse bands, unresolvable into lines with 

 a spectroscope of three prisms. These bands had their maxima 

 in places where the fine lines of the vapour were most intense 

 and most closely set, so that it might be inferred that they were 

 due to similar molecules in both cases, but that in the liquid the 

 vibrations of these molecules were no longer sharply defined, but 

 modified by the constraint arising from the liquid state. Some 

 parts, however, of the spectrum of the vapour, where the lines 

 were closely set, did not appear to be represented by any 

 definite bands in the liquid. The liquid absorbed a good deal of 

 blue light in a continuous manner, while the vapour only absorbed 

 it selectively. At the red end the limit of the visible spectrum 

 was lower for the liquid than for the gas — that is, there was more 

 absorption of red light by the vapour than by the liquid, so 

 much so that below a certain point the absorption by the vapour 

 appearted continuous. 



The narrow tube was next immersed in a wider tube full of 

 glycerine, which was gradually heated. As the temperature 

 rose, the colour of both liquid and vapour deepened, the absorp- 

 tions of the vapour were stronger, and the liquid gave the same 

 bands as had been before observed with the greater thickness. 

 At still higher temperature the absorption of blue light, both by 

 liquid and vapour, diminished sensibly, until at 85° the groups of 

 lines in the blue bad pretty well disappeared from the spectrum 

 •of the vapour. In fact, at 85° there was no sensible difference 

 between the actions of liquid and vapour on blue light, it seemed 

 •only some continuous absorption. At the red end the difference 

 between the liquid and vapour remained quite as strongly marked 

 as at lower temperatures — if anything, more so ; and the ab- 

 sorptions in the orange, yellow, and green were unaltered. At 

 90° the lines of the vapour in the green began to fade, and at 

 100° they were very faint ; but those in the orange, as well as 

 the corresponding diffuse bands in the liquid, were as strong as 

 before. There was still considerably more absorption of red 

 light by the vapour than by the liquid, as if there were a strong 

 absorption-band in the red of the vapour which was absent in 

 the liquid. 



As the temperature rose to 110° all the lines in the vapour had 

 become faint, and at 115° they were no longer discernible, and 

 there was no difference between the spectra of liquid and vapour 

 except in the red, and even here the difference was less marked 

 than at lower temperatures. At 130° no distinction was observ- 

 able between the spectra of liquid and vapour ; there were no 

 lines or bands in either, but a good deal of general absorption. 

 Liquid and vapour were dark, and appeared much of a colour, 

 but the meniscus at the junction was quite evident. The tube 

 was further heated to 155", but no further change was noticed in 

 the spectrum. On gradually cooling the tube, at ir2° the least 

 refrangible band in the orange was seen coming in both in vapour 

 and liquid, diffuse in both. At 100'' the usual lines were well 

 seen in the orange, yellow, and citron of the vapour, faint lines 

 in the green, and none in the blue ; and subsequently the 

 appearances presented on heating followed in the reverse order. 

 A solution of NjO^ in carbon bisulphide gave, in a thickness 



of 7 or 8 cm., diffuse absorption-bands in the green and citron, 

 ill-defined as in liquid N2O4 and in corresponding positions. In 

 a thickness of I cm. these bands were no longer visible. 



These observations bear out the supposition that pure N2O4 is 

 without selective absorption of the visible rays, and that the ab- 

 sorption observed is due to NO5, both in the vapour and liquid, 

 this absorption being modified in the liquid by the state of 

 solution in which the molecules have much less freedom. As 

 the temperature rises, the proportion of NOj increases, and at 

 the same time the density of the vapour increases and the free- 

 dom of motion of the molecules is diminished, they are less able 

 to assume the more rapid vibrations, and those which they do 

 as'^ume become less sharply defined, so that the lines fade into 

 bands and ultimately into a general absorption. 



Chemical Society, June 4. —Dr. W, J. Russell, F.R.S., 

 President, in the chair. — Prof. Mendeleeff's Faraday Lec- 

 ture on the periodic law of the chemical elements, was read 

 by the Secretary, owing to the enforced absence of the lecturer. 

 At the conclusion of the lecture, a vote of thanks to Prof 

 Mendeleeff was moved by Prof. Frankland, and seconded by 

 Sir F. A. Abel. The Faraday Medal and a purse were then 

 presented by the President to Mr. Anderson, by who n it was 

 received on behalf of Prof. Mendeleeff. 



June 6. — Dr. W. J. Russell, President, in the chair. — The 

 following papers were read ; — Experimental i-esearches on the 

 periodic law. Part I., by Dr. B. Brauner. The author gives a 

 detailed account of his attempts to determine the atomic weight 

 of tellurium by as many different methods as possible ; in all, 

 eleven were adopted, but each gave a different reult, varying 

 from 125-140. He eventually succeeded, but with great 

 difficulty, in preparing what appeared to be pure tellurium 

 telrabromide, and on most carefully analyzing this, obtained the 

 value Te= 1 27 '64 (0 = l6). This number, however, is incom- 

 patible with the position of tellurium in the periodic system, and 

 having satisfied himself that there were no experimental errors 

 which could account for the discrepancy, the author was forced 

 to conclude that what had hitherto been regarded as pure 

 tellurium contained foreign elements. By submitting tellurium 

 solutions to a systematic fractional precipitation, he has, in fact, 

 succeeded in obtaining a variety of substances, some of which 

 are undoubtedly novel elements. One of these it is proposed to 

 call Austriacum {Austriuni). In all probability this is the Dvi- 

 tcllurium (212), the probable existence of which was pointed 

 out for the first time by Mendeleeff in his recent Faraday Lecture. 

 From analyses made with material the uniformity of which is not 

 yet quite established, the author is satisfied that the atomic 

 weight of the element in question approaches very closely to 

 that indicated by Mendeleeff. In addition, there is at least one 

 other novel constituent, and this appears to be more or less 

 closely allied to arsenic and antimony. It follows that true 

 tellurium has yet to be discovered, and that its atonic weight 

 and properties remain to be determined. — The amylo-dextrin of 

 W. Nageli, and its relation to soluble starch, by Mr. H. T. 

 Brown and Dr. G. H. Morris. Amylo-dextrin, described by 

 \V. Nageli in 1874, is prepared by the long-continued action of 

 cold dilute acids on intact starch granules ; when purified by 

 dissolution in water and precipitation with alcohol, it forms 

 crystalline spherules, cbsely resembling those of inulin. The 

 authors consider amylo-dextrin to be analogous in composition to 

 the malto-dextrin previously described by them (Chem. Soc. 

 Trans., 1885, 528), and assign to it the formula CjoHooOn -f 

 (C]oH2o0^j)g ; i.e. it may be regarded as constituted of one amylon 

 or maltose group in combination with six amylin or dextrin groups. 

 Soluble starch, with which amylo-dextrin has frequently been 

 confused, is converted into a mixture of maltose and dextrin 

 on treatment with diastase, whilst amylo-dextrin yields maltose ex- 

 clusively ; moreover it is shown that soluble starch is the first 

 product of the action of cold dilute acids on starch, and that this 

 is slowly hydrolyzed to amylo-dextrin, a portion cf the starch 

 substance at the same time going into solution as dextrose. — The 

 determination of the molecular weights of the carbohydrates 

 Part II., by the same. As determined by Raoult's method, 

 galactose and malto-dextrin are found to have molecular 

 weights corresponding with the formula CgHijOg and 

 Ci^Hg.jOji . (C].jH2(,Oi„)2 respectively. For inulin the formula 

 2(C3(jH(.203i) is deduced, and in view of the great similarity in 

 physical properties between inulin and amylo-dextrin the authors 

 are inclined to regard the two substances as closely analogous in 

 composition, representing inulin by the formula (012^22011)2 "^ 



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