54 



NA TURE 



[Novem!;i-;r 17, il 



where abed axe any monovalent radical not containing an asym- 

 metric carbon atom, while R is a dextro-rotatory bivalent 

 radical. The first molecule formed, according to equation (i), 

 will have the underlined C dextro or laevo, being determined by 

 R being dextro. 



When this decomposes according to equation (2) the C^will 



G/,H ~ 



still be active, and one active molecule of I will have been 



CabH 

 produced. ~ 



But RH., is reproduced, and is consequently capable of repeat- 

 ing this action indefinitely, and of making an indefinite number 



CAH 

 of I molecules with activity of the same sign. 

 Cain 



Furthermore, this action is scarcely to be distinguished in 

 principle from the reactions brought about by unorganised 

 ferments or enzymes. W. M. Strong. 



Helstonleigh, Champion Park, Denmark Hill, S.E., 



November I. 



It appears to me that Prof. Kipping and Mr. Pope unin- 

 tentionally attribute to me opinions which I have never 

 expressed, and which I do not hold. I never for a moment 

 imagined that in each separate eryslallisalioii—e\\.hex of 

 molecularly symmetric substances which, like sodium chlorate, 

 may form either right-handed or left-handed crystals, or of the 

 externally compensated mixture of dextro- and laevo-rotatory 

 sodium ammonium tartrates, in which the asymmetry is 

 molecular — equal amounts of the two kinds of crystals would 

 necessarily be deposited. I never thought of this equality as 

 holding good, except as the mean of a great number of experi- 

 ments. In my address, when referring to Messrs. Kipping and 

 Pope's results obtained with sodium chlorate, I therefore used 

 the expression "on the average." Besides, I was acquainted 

 with Landolt's experiments on the subject, which prove the 

 same thing. In the case of the dextro- and laevo-rotatory 

 sodium ammonium tartrates, the Pasteur-Gernez method of 

 separating these by starting the crystallisation with a crystal of 

 one of the two kinds, and Jungfleisch's experiments, to which I 

 will refer more fully later on, were sufficient to make me aware 

 of the influence of initial bias on crystallisation, and to prevent 

 me from expecting equality, except as a mean result. 



In fact, in these crystallisations everything depends on this 

 initial bias ; and in this respect, Landolt's experiments are 

 especially instructive. His method (Be>: d. deiitseh. ehem. Ges., 

 1896, p. 2410) consists in precipitating aqueous solutions of 

 sodium chlorate by addition of alcohol. \ magma of minute 

 crystals is thus obtained, each of which must be either right- 

 handed or left-handed. The crystals are then separated and 

 ground to a fine powder ; and this powder, suspended in a 

 mixture of alcohol and carbon disulphide, is examined in the 

 polarimeter. II both enanliomorphous forms are present in 

 equal quantity, there will be no rotatory effect ; whereas a 

 preponderance of either form will be indicated by a rotation in 

 the corresponding sense. 



Landolt found that if the precipitation was rapidly effected by 

 the sudden addition of alcohol, the powder was either inactive, 

 or had a very feeble rotation. On the other hand, if the alcohol 

 was gradually added, so as to produce slow precipitation, the 

 powder displayed a marked rotation, which was in some cases 

 right-handed, in others left-handed. The reason is obvious. 

 In the former case, the crystallisation starts .simultaneously from 

 a vast number of independent centres ; the chances are equal in 

 favour of each centre being right-handed or left-handed; each 

 centre will propagate its own kind ; and thus the ratio of right- 

 handed to left-handed forms will not difler very appreciably 

 from unity. In the latter case, as' Landolt points out, the 

 crystallisation starts from only a few centres ; in these, 

 therefore, either the right-handed or the left-handed form may 

 predominate, and, as suflicient time is given, the dominant form 

 will influence the course of the crystallisation. 



In Messrs. Kipping and Pope's slow crystallisations, every 

 opportunity is afforded for any initial asymmetric bias to 

 exercise its influence ; and I should have been greatly surprised 

 if the authors had obtained a result other than that w hich the) 

 describe. 



There is, therefore, a marked difference between tb4 

 formation of enanliomorphous crystals and of enantiomorpha 

 molecules respectively, under symmetric conditions : namely *1 

 that the crystals propagate their own asymmetry, whilst tlie 

 molecules, as I pointed out in my reply to Prof. K.arl Pearsor, 

 do not — at least, so far as experiment informs us 



In the crystallisation of the externally compensated mixtnie 

 of dextro- and laevo-rotatory sodium ammonium tartrates, or- 

 would expect a .similar state of things to prevail, modifiel 

 however by the circumstance that in this case, the two opposite 

 asymmetries of the molecules themselves are pre-existent in the 

 solution and must influence the result. One would expec' 

 variations, within limits, of the relative quantities of dextro- an.l I 

 laevo-salts deposited ; but according to our present views, Ihc 

 mean variations should oeciir equally in opposite directions. 



It is therefore with great surprise that I learn that in the ten 

 experiments which Messrs. Kipping and I'ope have hitherti^ 

 made on this point they obtained in every case a strongly 

 dextro-ro'atory deposit. It is true that Jungfleisch (compare 

 Chem. News, vol. 40, p. 231) published, in 1SS4, similar 

 results. Jungfleisch's procedure was somewhat different from 

 that of >iessrs. Kipping and I'ope. In.stead of allowing the 

 solution to crystallise spontaneously, he introduced simul 

 taneously into the supersaturated solution, at opposite sides or 

 the crystallising dish, a crystal of the dextro-rotatory and onv 

 of the laevo-rotatory salt. In all his experiments the former 

 crystal increased in weight, and the mother liquor contained ^ ' 

 corresponding excess of the laevo-salt. I confess that I hav 

 always attributed Jungfleisch's results to mere coincidence. I 

 will doubtless be within Prof. Kipping's recollection that in 

 April last I wrote to him calling his attention to these results, 

 in connection with his joint work with Mr. Pope. Proi 

 Kipping replied (I quote from memory), that Jungfleisch - 

 results were opposed to all that was known of the behavioui 

 of enantiomorphs ; that he (Prof. Kipping) did not regard then 

 as conclusive ; and that he proposed to repeat them. This h^ 

 and Mr. Pope have now done ; but from what I have just said, 

 it is evident that the outcome of this repetition must have 

 been as great a surprise to him as it is to me. I am glad to 

 find, however, that the authors put forward their results withlj 

 reserve, and that they contemplate the possibility of discoveringl 

 some disturbing influence. If no such influence is at work, it I 

 is not merely the small matter of my particular application ofl 

 the principles of molecular asymmetry that will have to go : it I 

 is these principles themselves. But I do not anticipate anyll 

 such catastrophe. The vast accumulation of verified prediction ' 

 of which the science of stereochemistry can boast, does no; 

 point to premises so unsound. 



I will wait, therefore, for further light on Messrs. Kipping 

 and Pope's later experiments before drawing any conclusion 

 from them. As regards the experiments with sodium chlorate. 

 I am at a loss to understand in what way they militate against ■, 

 my views. I no more expect equal numbers of right and left jj 

 crystals to separate in any given crystallisation of sodium chlo- 1 

 rate than I expect an unvarying alternation of heads and tails • 

 in tossing a coin. Nor do I perceive the application of the 

 experiment in which they obtained none but right-handed 

 crystals of the chlorate ; inasmuch as, if they go on repeating 

 it, they will obtain, just as often, none but left-handed crystals. 

 The process will not constantly yield the same form. 



I must also rejieat that I do not regard the s(K>ntaneou- 

 formation of "optically active mother liquors," or other partial 

 separations of enantiomorphs, especially when the separation 

 may occur in either direction, as a solution of (he problem. The 

 separation of enantiomorphs in the living world is, in the over- 

 whelming majority of cases, as I have pointed out in a previous 

 reply, not partial but total ; and it occurs constantly in one 

 direction —only one form survives. This is another case wher> 

 the word "constantly " applies — a word quoted by the author-^, 

 but otherwise ignored by them, excejit where they are discus? 

 ing experiments which they themselves regard as requirini; 

 confirmation. 



I think, moreover, that my critics might in justice take int" 

 account the disadvantage under which I laboured in having t 

 compress into the limits of a brief address an account of a su! 

 ject so vast and intricate. Many of my statements of imiwrtar. 

 points were necessarily somewhat summary- and inadequate 

 and most of the misunderstandings into which my variou- 

 critics have fallen are, I am aware, due to this circumstance. 



The University, Aberdeen, November 10. F. R. J.^rr. 



NO. I 5 16, VOL. 59I 



