642 



NATURE 



[July 22, 1920 



sary quality and are then put on the market, it appears 

 that there will not be any great risk of foreign com- 

 petition in the. matter of price. Indeed, according to 

 several correspondents, there is little to be feared at 

 the present time. But opinions are not in agreement. 

 There should be no objection to " manutacturers' 

 associations," provided that their object is to obtain 

 the advantage of more economical methods of manu- 

 facture, as by uniformity of standards and larg:e-scale 

 production, rather than the maintenance of high 

 prices. 



The cost of all research work, whether paid for by 

 Government grants or otherwise, is greatly increased 

 by inferior apparatus. At the present prices of mate- 

 rials, a single biochemical preparation may cost 4L or 

 5Z. or more. This may be lost by breakage at the 

 final stage. The question naturally arises whether 

 economy would not be effected by allowing free im- 

 port, even at the cost of subventions to British makers. 

 With reference to Mr. Watson Baker's statement 

 (Nature, June 24, p. 518) that there are j2,ooo 

 German binoculars in London, I confess that I had 

 chiefly in mind the use of apparatus in teaching and 

 research. The sale for general use certainly raises a 

 difficulty. As to losses incurred by work done for 

 Government Departments during the war, so far as 

 my information goes payment for these did not err 

 on the side of economy. Liability for excess-profit 

 duty surely implies that the profit has been made. 



The statement by Mr. C. Baker (Nature, May 20, 

 p. 356) that capitalists will not put money into the 

 business raises another question. It may well be 

 that British makers do not find it profitable to 

 undertake the supply of fine chemicals and special 

 apparatus used only in small amount, even apart from 

 foreign competition. If so, why not give up the trade 

 to those who make a profit on the sale? 



The desire of the British industry for prohibition 

 of import appears to rest chiefly on the fear of com- 

 petition by Germany. I am not one of those who 

 imagine that because an instrument is of German 

 origin it is necessarily superior to all others. Indeed, 

 I have heard of instruments verified at Charlotten- 

 burg being found inaccurate. It would certainly be 

 less obstructive than total prohibition if the restric- 

 tion applied to German goods only. But there are 

 other considerations to be remembered here, such as 

 the importance of giving an opportunity to that country 

 to restore its credit. However this may be, the large 

 profits of their chemical industries referred to above 

 raise some doubt as to the real cause of the present 

 unsatisfactory conditions in Germany. 



The point raised by Mr. Dunkerly that American 

 microscopes and lenses are being sold here, although 

 the rate of exchange is against us, suggests that the 

 source of the trouble is not the low value of the 

 German mark. This view is confirmed by other cor- 

 respondents. If it is correct, there would be no 

 real gain in a mere prohibition of import. Improve- 

 ments in modes of manufacture are needed, and we 

 come back again to the necessity for more scientific 

 research. 



I note that the British Optical Instrument 

 Manufacturers' Association (Nature, May 20, 

 P- 3SS) considers that a tariff might have the 

 result of removing the inducement to improve quality, 

 but I foresee so many difficulties in the wav of 

 convincing a Government official that a particular 

 piece of apparatus could not be obtained in England 

 that I am unable to accept the suggestion of import 

 by permit as a satisfactory alternative. If, however, 

 it were possible for every scientific worker to obtain 

 without difficulty a general permit for the import of 

 NO. 2647, VOL'. 105] 



any • apparatus at any time the situation would be 

 different. 



There seems, to be much doubt as to whether it is 

 really possible to obtain foreign apparatus at a price 

 much lower than the British. Should this be the 

 case, the payment of a subsidy might be considered 

 where there is actual underselling. The test would 

 then become one of quality. 



The importance of the subject may, I think, serve 

 as an excuse for this lengthy letter. Scientific workers 

 have every desire to assist the development of ths 

 industry, but they feel that they are not justified in 

 wasting time and money where it could be avoided. 

 And if this correspondence has brought out the fact 

 that satisfaction has not yet been given in the matter 

 of quality, especially in the case of certain goods, it 

 will have been of some value. It is possible that 

 users have not sufficiently made known their difficul- 

 ties to the makers, and have been sometimes content 

 with the purchase of foreign material when further: 

 inquiry and discussion might have enabled British 

 goods to be forthcoming. W. M. Bayliss. 



University College, London. 



The Separation of the Isotopes of Chlorine. 



Mr. D. L. Chapman's argument appears essentially 

 to be similar to that already developed from a quite 

 different point of view by Lindemann {Phil. Mag., 

 1919, vol. xxxvii., p. 523; vol. xxxviii., p. 173), that 

 because isotopes are (theoretically) separable by 

 physical means, they must also be chemically se|>ar- 

 able according to thermo-dynamical reasoning. The 

 fact that the particular mode of separation by semi- 

 permeable membranes (assumption (3), Nature, 

 July 15, p. 611) is highly fanciful need not obscure 

 the nature of the argument. Lindemann 's conclusion 

 that, though isotopes cannot be identical chemically,, 

 the difference may be reduced to an unmeasurable on© 

 of the second order of magnitude by suitable assump- 

 tions as to the " Nullpunktenergie," seems to indicate 

 the more hopeful line of advance. The chemical non- 

 separability of isotopes, of which there is an accumu- 

 lated mass of experimental evidence, seems to call for 

 consequent adjustments in thermo-dynamic theory 

 rather than the reverse. 



The following considerations mav throw light on 

 the matter. I have stated (Nature," June 24, p. 516) 

 that, on the assumption of the chemical identity of 

 the isotopes, the distribution given by probability con- 

 siderations of the two kinds of atoms among the 

 three kinds of molecules is 



CI, :C1', :'C1.C1': :n^:(i-n)^:2n(i-n) . (i) 

 where n and (i — n) are the fractional proportions of 

 the CI and CI' atoms respectively. This leads to the 

 equilibrium condition 



[CL][C1',] = J[C1.C1']=' .... (ii) 

 Now if one applies in the conventional manner this 

 result to the reversible reaction * 



CL+C1',^2C1.C1', 

 denoting by fej and fe, the coefficients of velocity of the 

 direct and the inverse reactions, one gets 



k,n'ii-nY = k,{2nii-n)y 

 or 



fel=4fe2. 



This, to say the least, is unexpected, because if co- 

 efficients of velocity of reaction have any physical 

 significance at all, one would expect them to be the 

 same for substances assumed to be chemically iden- 

 tical. The result is clearlv due to a loose method of 



