HEMTOSIN. 219 



These numbers approach so near those obtained by analyzing 

 isinglass and common collin, that we cannot hesitate to consider 

 it as isomeric with these bodies. 



CHAPTER III. 



OF HEMATOSIN. 



THIS name was given by Chevreul to the colouring matter of 

 blood, which Dr Wells,* as early as 1797, showed to be"an animal 

 substance of a peculiar nature. Vauquelin and Brande pro- 

 posed processes for obtaining it in an isolated state, but they did 

 not succeed in freeing it from the albumen with which, in the 

 crassamentum of blood, it is always united. Berzelius and En- 

 gelhart proposed other processes ; but what these chemists con- 

 sidered as hematosin was in reality a compound of hematosin and 

 albumen. And as the albumen greatly "preponderated in point 

 of quantity, the characters which they assigned to the colouring 

 matter were very nearly those which belonged in reality to al- 

 bumen. . 



M. Lecanu, in his thesis published in 1837, has given the fol- 

 lowing process for obtaining pure hematosin.f Into human 

 blood deprived of its fibrin by agitation with a rod, pour sulphu- 

 ric acid, drop by drop, till the liquor, which assumes a brown 

 colour, coagulates into a thick magma. Dilute this magma with 

 alcohol, which causes it to contract in bulk. Put the whole into 

 a cloth, and subject it to sufficient pressure to squeeze out the al- 

 cohol together with the water formerly contained in the blood. 

 What remains in the cloth has a brown colour. It is to be re- 

 duced to small particles, and treated repeatedly with boiling al- 

 cohol, (the last portions of which must be acidulated,) till the li- 

 quid-ceases to assume a red colour. 



The alcoholic solutions are left at rest till they are quite cold, 

 and then filtered to separate a quantity of albumen which will 

 have precipitated. The filtered liquid must be saturated with 

 ammonia, and then filtered again to get rid of some sulphate of 



* See Phil. %g. xvi. 154. 



f Etudes Chimiques sur le sang humain, p. 28. 



