Royal Society. 391 



who perhaps in most cases have neither time nor inclination to 

 devote much attention to the study of chemistry for its own sake, 

 it would be unfair to charge upon it as a fault that it follows the 

 most commonly received system of instruction in the science, even 

 although we may be of opinion that that system is not the best 

 possible. 



We have exceedingly little to say in the way of adverse criticism 

 on the details of this work. Here and there, possibly, are signs of 

 somewhat hasty composition or correction : to this cause, for instance, 

 we attribute the occurrence of such an expression as " oil of vitriol 

 plus its own bulk of water " on page 77, an expression which is much 

 less pleasant than " oil of vitriol diluted with its own bulk of water," 

 which we find on the following page. Again, on page 17 we are 

 told that solutions of silver yield " a buff precipitate with hydrate of 

 soda," where for hydrate we are doubtless intended to read carbonate. 

 The method of preparing absolute alcohol, recommended on page 13, 

 might likewise be improved; for alcohol can be more completely and 

 easily dehydrated by using a sufficient quantity of good quicldime 

 than by either carbonate of potash or sulphate of copper. 



In conclusion, we have again to express our conviction that Mr. 

 Church has produced a book well qualified to be of use to those to 

 whom it is addressed ; and if we have suggested a plan by which, 

 without increasing the size of the book, its utility might, in our 

 opinion, be made still greater, it is by no means because we con- 

 sider its value small in its present shape. 



XLIX. Proceedings of Learned Societies. 



ROYAL SOCIETY. 

 [Continued from p. 320.] 

 June 16, 1864. — Major-General Sabine, President, in the Chair. 



THE following communication was read : — 

 " On the Reduction and Oxidation of the Colouring Matter 

 of the Blood." By G. G. Stokes, M.A., Sec. R.S., &c, 



1 . Some time ago my attention was called to a paper by Pro- 

 fessor Hoppe*, in which he has pointed out the remarkable spec- 

 trum produced by the absorption of light by a very dilute solution 

 of blood, and applied the observation to elucidate the chemical nature 

 of the colouring matter. I had no sooner looked at the spectrum, 

 than the extreme sharpness and beauty of the absorption-bands of 

 blood excited a lively interest in my mind, and I proceeded to try 

 the effect of various reagents. The observation is perfectly simple, 

 since nothing more is required than to place the solution to be tried, 

 which may be contained in a test-tube, behind a slit, and view it 

 through a prism applied to the eye. In this way it is easy to verify 

 Hoppe' s statement, that the colouring matter (as may be presumed 

 at least from the retention of its peculiar spectrum) is unaffected by 



* Virchow's Archiv, vol. xxiii. p. 446 (1802). 



