130 



Report of Schimmel s Co. April 1913. 



the required water was placed within the still itself. The distillates obtained were 

 fractionated with a Glinski apparatus. The results were as follow: — 



Distillation with water: 



Oil driven off di 8 ,5o 



104,0 cc. 0,7824 



103,8 „ 0,7826 



Distillation without water: 

 Oil driven off di 8 , 5 o 



103.4 cc. 0,7864 



103.5 „ 0,7865 



Fractionation of the distillate: 

 B. p. 105 to 125° 125 to 140° 

 22,9 p. c. 25,6 p. c. 



22,5 „ 23,8 „ 



Fractionation of the distillate: 

 B.p. 108 to 125° 125 to 140° 

 15,8 p. c. 19,8 p. c. 



17,1 „ 20,3 „ 



It would appear to us that the theoretical foundation, namely the generalisation 

 of Margules' formula, does not appear to be quite correct, but we do not desire to 

 make further observations on the matter in this place, because it is our intention, 

 when an opportunity offers, to deal experimentally with the subject in question. 



On p. 133 of our last October Report we discussed a method which has been 

 worked out by E. Deussen for testing the purity of optically active substances. In a 

 second communication on the same subject, Deussen 1 ) publishes further experimental 

 results. Of particular importance in his method is the accurate determination of the 

 optical rotation, as an error of even a hundredth part of a degree very considerably 

 affects the value of the specific rotation, hence it is necessary to read off 8 or 10 times. 

 Shortly after the publication of Deussen's second article, L. Tchugaeff-) published 

 certain notes on Deussen's work. Tchugaeff has ascertained that Deussen in his 

 careful investigation of the literature on the subject has overlooked precisely the work 

 of those authors 3 ) who since the year 1896 have been engaged in the study of the 

 conditions of rotation of coloured compounds and of compounds showing abnormal 

 rotatory dispersion generally. Tchugaeff further specially points out that about 18 months 

 ago 4 ) he himself proposed a method by which it is possible to utilise the rotatory 

 dispersion for the analysis of optically active mixtures to a far wider extent than can 

 be done by Deussen's method. In conclusion, Tchugaeff points out that the mono- 

 chromatic mercury light used by Deussen cannot have a wave-length of 491 pp, as 

 stated by Deussen, but of 546/'/'. Herein Deussen 5 ) agrees with Tchugaeff, but 

 he also observes that in his experiments he made use of a solution of potassium 

 bichromate, Guinea-green-B-extra and aesculin, which, according to a reference in the 

 book by Plotnikoff {Photochem. Yersuclistechnile, Leipzig 1912, p. 20) ought to give a light 

 of 491,6/'// wave-length, but which actually probably only allows of the penetration 

 of a light of 546/'//. Deussen nevertheless remains convinced that in the testing of 

 the purity of optically active bodies he has gone a step in advance of Tchugaeff, since 

 he has pointed out how it is possible to recognise the absolute purity of an optically 

 active substance. 



Finally there remains to be mentioned a rejoinder by Plotnikoff ) to Deussen's 

 statement. Plotnikoff points out that any colouring material, given a sufficiently weak 



x ) Joum. f. prate. Chem. II. 86 (1912), 425. — 2 ) Ibidem 545. — 3 ) Tchugaeff here quotes 18 literary 

 references. — 4 ) Zeitschr. f. physik. chem. 76 (1911), 469. — Berl. Berirhte 45 (1912), 1293. - 5 ) Journ. f. 

 prakt. Chem. II. 87 (1913), 96. — a ) Ibidem 236. 



