On the Proteid Reaction of Adanikiewicz, &c. 



21 



extent, determinate, if we combine with the general theorem the condi- 

 tions of continuity of state of the dielectric on the two sides of the 

 aperture. The determination is practically complete when the medium 

 •©n the nearer side is the dielectric plate of a condenser, in which 

 ^electric vibrations are taking place ; and the result can be applied to 

 determine the rate of decay of the vibrations due to transference of 

 the energy to the external dielectric. The example of a condenser, 

 with concentric spherical conducting surfaces, the outer conducting 

 sheet being perforated by a small circular aperture, is worked out in 

 detail ; and the results suggest that the maintenance of the vibrations 

 depends on the screening action of the outer conductor rather than 

 ©n the largeness of the capacity of the condenser ; in fact, the vibra- 

 tions of the spherical condenser are much more slowly clamped when 

 the capacity of the condenser is small than when it is large, the outer 

 conductor and the aperture remaining the same. 



f* On the Proteicl Eeaction of Adanikiewicz, with Contributions to 

 the Chemistry of Glyoxylic Acid." By F. Gowland 

 Hopkins, M.A., M.B., University Lecturer in Chemical 

 Physiology, and Sydney W. Cole, B.A., Trinity College. 

 (From the Physiological Laboratories, Cambridge.) Commu- 

 nicated by Dr. Langley, F.E.S. Eeceivecl January 7, — Eeacl 

 February 7, 1901. 



In 1874 Adamkiewicz* described the now familiar reaction which 

 results in the production of a violet colour when strong sulphuric acid 

 is added to the solution of a proteid in glacial acetic acid. Adani- 

 kiewicz did not apparently look upon the employment of the acetic 

 acid as introducing anything beyond a certain modification of the 

 action of sulphuric acid. His original communication opens with a 

 description of the colour phenomena seen when egg-white is dissolved 

 in strong sulphuric acid : and he begins the description of this reac- 

 tion, since associated with his name, by speaking of " a special influence 

 which the presence of glacial acetic acid has upon the colour' of the 

 sulphuric acid proteid solution." The view has since been generally 

 held that the coloured product of the reaction arises entirely from the 

 proteid molecule itself, as the result of an interaction between pre- 

 cursors liberated under the influence of the strong acids employed. 



Y. Udranszkyf believed that the colour change which occurs is, as a 

 matter of fact, to be classed as a furfurol reaction. It is therefore to 

 be compared with the result of such a procedure as that of Molisch's 



* ' PMger's Archiv/ 1874, toI. 9, p. 156. 



f ' Zeitsch. f. physiol. Chem.,' 1888, toI. 12, p. 395. 



