ABSORPTION SPECTRA AND CHEMICAL CONSTITUTION. 167 



it does not appear likely that a substance of the character of albumen, 

 ■vyhose mode of vibration, as shown by its absorption spectrum, differs 

 widely from that of the carbohydrates, could affect the latter, while on 

 the other hand it is possible that the intramolecular vibrations of inver- 

 tase and diastase might be communicated to saccharose and stai-ch. That 

 the sugars are highly diactinic substances is quite in character with what 

 we know of their constitution and of the spectra of similarly constituted 

 substances. 



It is of interest to learn that the albuminoid compounds associated 

 with the carbohydrates are evidently different in constitution from those 

 forms of albumen found in the animal organism. The probability pre- 

 sents itself of these albuminoids being derived from the carbohydrates. 



Isomorplious Derivatives of Benzem. — Report of the Committee, con-' 

 sisting of Professor H. A. MiERS (Chairman), Dr. W. P. Wynne. 

 and Dr. H. E. Armstrong (Secretary). {Vraivn up hij the Secre- 

 tary.) 



The existence of morphotropic relationships between the crystalline 

 forms of substances which are not isomorphous in the formal sense of the 

 term has of recent years acquired new importance, the purely geometrical 

 work of Barlow ' and others having demonstrated the superfluity of the 

 old view that the units of the crystalline structure are polymerides of the 

 chemically active fundamental molecule as a means of explaining poly- 

 morphism and kindred crystallographic phenomena, whilst Fock - has 

 shown, from the study of the partition coefficients of two isomorphous 

 substances in equilibrium in a liquid and a solid solution in contact, that 

 in the case of salts, at all events, the molecular weight in the crystalline 

 state may be that of the fundamental molecule. Moreover the work of 

 Paterno •' and others on the cryoscopic behaviour of substances jjossessing 

 constitutions similar to that of the solvent indicates with certainty that 

 isumorphism and morphotropy are phenomena which merge gradually one 

 into the other. 



The consideration of facts such as these leads to the conclusion that 

 moi'photropy and isomorphism have a common cause, and that this is 

 more likely to be discovered by the crystallographic study of substances 

 showing morphotropic relationships than from the examination jnerely of 

 materials likely to exhibit isomorphism. 



The benzene series offers exceptional oppoi-tunities for the study of 

 such questions ; indeed, it is remarkable that the publication of Groth's 

 important memoir,"' calling attention to the existence of morphotropic 

 relationships between benzene derivatives, has not acted as an incentive 

 to really systematic work on the subject. 



The two investigations to be referred to form part of a series which are 

 being carried on in the chemical department of the Central Technical 

 College, South Kensington, in order, as far as possible, to determine the 

 effect on the crystalline form of certain definite changes in the composi- 

 tion. The work will include the determination of the molecular volumes 



' Proc. Jloi/. I)iih. .Soc, 18'J7, viii. 527. -' Xriff.f. A'ri/st., 18!)7, x.xviii. 337. 



» Gazzetta, 1895, xxv. 1, 411. < Po/fff. Ann'., 1870, 141, 31. 



