March 17, 1921] 



NATURE 



n 



origin of the substance, nothing more; "carbamide" 

 is suggestive of a particular structure, of a view 

 which, so long as I can remember, has not been in 

 accordance with the facts and is now, I suppose, 

 fairly generally abandoned, though the error is still 

 perpetuated in the text-books — but one of the main 

 purposes text-books serve is the perpetuation of error. 

 Other cases might be quoted; time was when "con- 

 stitutions " were settled on paper and not a few 

 names are survivals of the practice. 



In a course of Cantor lectures on " Food Problems " 

 which I gave in May, 19 19, I suggested the use of 

 the term " advitant " in place of " vitamine." A word 

 of good clang, its meaning is clear and will be 

 obvious to most ; the substances it is intended to 

 cover are necessary to life and we may as well say 

 so, though we have not the faintest idea what they 

 are. Henry E, Armstrong. 



Relativity and the Velocity of Light. 



Mr. Bartrum's excellent letter on p. 42 of Nature 

 of March 10 has done good service in extracting an 

 explanation from Dr. Jeans, but the latter will for- 

 give my saying that his position is not clear yet, at 

 least not clear to me. Briefly thus : 



(a) If we are able to compare the velocities of two 

 single light journeys, one of which may be under 

 normal conditions and therefore known, surely we 

 have determined the other. 



(b) I cannot see that Majorana's interesting experi- 

 ments prove more than that the propagation of light 

 has the characteristics of wave, and not projectile, 

 motion. 



(c) I admit Dr. Jeans's equations (i), (2), and (3), 

 but I can see no merit in afterwards introducing v. 

 If they are true for all reasonable values of it, what 

 more is gained by writing ii-Vv instead of tt? Are they 

 not the same thing? Oliver Lodge. 



The Peltier Effect and Low-temperature Research. 



From certain considerations emphasised by me in 

 the PMl. Mag. for December (Supplement), 1876, 

 especially § 33, ser. v., vol. ii., p. 538, about true 

 contact e.m.f., I concluded that such forces are inti- 

 mately connected with electrical resistance ; good con- 

 ductors fail to get a grip on the electricity so as to 

 propel it effectively, while the grip of insulators is 

 tremendous. Consequently it is probable that at any 

 temperature at which electric resistance ceases, the 

 Peltier effect will cease also. Oliver Lodge. 



The Nature of the Emulsoid Colloid State. 



The publication in the Transactions of the Chemical 

 Society for December last of the latest of the ex- 

 tremely valuable and interesting investigations by 

 Prof. J. W. McBain and his collaborators on soap 

 solutions leads me to direct attention to a hypothesis 

 as to the nature of the emulsoid colloid state which 

 I have briefly indicated in a technological paper on 

 "Colloidal Fuels" {Journ. Itid. Eng. Chem., vol. xiii.. 

 p. 37, 192 1 ). The stabilising colloids used in thesft 

 fuels belong to a class of bodies forming emulsoid 

 sols and gels in non-aqueous systems, e.g. ia hydro- 

 carbon oils. The parallelism between certain such 

 non-aqueous systems and aqueous emulsoids has 

 struck many observers (notably M. Fischer) and caused 

 considerable doubt as to the validity of the applica- 

 tion of ionisation theories to the emulsoid colloids. 

 Certainly it would appear that any theory of the 



NO.. 2681, VOL. 107] 



emulsoid systems must explain why sodium oleate 

 forms sols and gels with water, whereas aluminium 

 oleate does so with benzene. 



The theory of micellar orientation supported by 

 McBain appears to suffer in this respect, that the 

 "micelle" postulated is already a micro-colloid 

 system, and the colloid properties are already present 

 in the "micelle." A consistent theory of emulsoids 

 must not only be in agreement both with the physical 

 properties (viscosity of sols, gelation, elasticity of 

 gels, hysteresis, etc.) and with the facts as to chemical 

 constitution (polysaccharide character of starches and 

 celluloses, polypeptide character of proteins, fatty 

 acid salts for soaps, etc.), hut it should also show 

 the physical properties developing from the chemical 

 composition and constitution. If colour and selective 

 absorption flow from chemical composition and con- 

 stitution, there appears no reason why cohesion and 

 selective adsorption should not do so also. The sug- 

 gestion which I put forward was stated as follows {loc. 

 cif.,p. 42) : — "Such gels — (heat reversible) not coagula 

 — may be imagined as very tenuous web-works, or 

 foams, the mesh or walls of which are very probably 

 sub-molecular in dimensions, or the whole mass of 

 the colloids forms one ' molecule ' uniformly dispersed 

 through and partially dissolving the solvent. By 

 partially I inean that only part of the * molecule ' of 

 the emulsoid is consolute with the solvent or dis- 

 pergent, while the other part of it is insoluble, and 

 its atoms tend to unite, forming a semi-rigid frame- 

 work." 



The hypothesis proposed does not regard micellar 

 orientation (and attraction) as primarily responsible 

 for emulsoid sols and gels, but rather sub-molecular 

 (or transmolecular) orientation of definite atom-groups, 

 entirely in the sense of the theory of molecular 

 orientation due to structure proposed for surface and 

 interfacial tension phenomena by W. B. Hardy (Proc. 

 Roy. Soc, vol. Ixxxvi., A, p. 610, 1912), J. Langmuir 

 (Journ. Amer. Chem. Soc, vol. xxxviii., p. 2221, 1916; 

 ibid., vol. xxxix., p. 1848, 1917), and W. Harkins 

 (Journ. Amer. Chem. Soc, vol. xxxix., pp. 354 and 



541. 1917)- 



The genesis of a micelle, as plurimolecular unit of 

 a colloid system, may be regarded as a consequence 

 of equilibrium, usually incomplete, between homo- 

 chemical solution forces and heterochemical forces, 

 the former tending to dissociate and decompose the 

 chemical molecule, the latter resisting decomposition. 

 In the case of proteins the most probable general 

 type of linkage, according to H. A. Plimmer 

 ("Chemical Constitution of the Proteins," part ii., 

 p. 2), is of the form 



NH.^CHR.CO.(NH.CHR.CO),..NH.CHR 



GOGH 



where n refers to the degree of polypeptide condensa- 

 tion and R is an alkyl or other substituent group. 

 On the hypothesis suggested here we may, imper- 

 fectly, represent the redistribution of this in the 

 presence of water for the polypeptide chain by 



Aqueous 



O 

 C- 



H 



-> 



-N- 



HOH 



6 

 -C- 



H 



• N 



HOH 



O 



\/ 





<- 



CHR (CHR) CHR (CHR) CHR 

 Lipoid \ ,/ / 



