ALBUMENS AND OTHER ORGANIC SUBSTANCES.^ — CREIGHTON. 68 



componnds are unstable and the albumen may be recovered by 

 treatment with acids, when it is precipitated and the metal 

 goes into solution. 



Physiologists have long divided iron compounds into two 

 classes; those which contain ''organic" iron, and those which 

 contain "inorganic" iron. Macallum^ has shown that haem- 

 atoyxlin may be used to distingiiish between these two classes 

 of compounds; and in the experiments which follow I have 

 employed this reagent to demonstrate the condition of the iron. 



The terms "bound" and "unbound", as used by Prof. Fraser 

 Harris are, I think, to be |)referred to the more ambiguous 

 "organic" and "inorganic". As even better than "bound" and 

 "unbound", however, I would suggest the use of the terms 

 "non-ionic" and "ionic' ; for inorganic or unbound denotes the 

 simple ionic state, while organic or bound denotes a condition 

 which is not elementary, but often quite complex. A compound 

 containing "ionic" iron would be one in which the iron exists 

 as a cation ; and in a compound containing "non-ionic" iron the 

 iron would not be present as a simple ion, but Avould exist as 

 part of a complex ion, usually as part of the anion. This classi- 

 fication is justified by experiment, for compounds such as ferric 

 chloride, ferrous sulphate, ferric acetate, and potassium ferri- 

 ferrocyanide (soluble Prussian blue), all of which contain a 

 simple iron cation, give a deep blue black or violet black 

 colouration with haematoxylin ; while, on the other hand, com- 

 pounds such as potassium ferricyanide or potassium ferro- 

 cyanide, in which the iron is not present as a simple ion, but 

 as part of a complex anion, give no reaction with haematoxylin. 



11. ExPERIMEiN"TAL. 



Albumen: A lofc white of egg solution, a 10;?^ solution of 

 Merck's "Egg Albumen granular", and a 10^ solution of 

 Merck's "Serum Albumen" were used in the following experi- 

 ments. The egg and serum albumen were dissolved in very 



1. Macallum, A. B. : J. Physiol, 22, 92, (1897-1898). 



