CHAP. II.] THE BLOOD. 117 



for the complete precipitation of the crystals and the solution of 

 the proteids. The whole mixture is then poured into a large beaker 

 and treated with many times its volume of water and set aside for 

 many days. The magma of crystals which has then fallen to the 

 bottom is washed many times in succession with water, and boiled 

 with strong acetic acid, as long as the crystals appear to be mixed 

 with masses of proteid matter ; they are then washed with water, and 

 collected on a filter and treated, first with alcohol, and then with 

 ether. Haemin crystals may also be obtained by adding water and 

 NaCl to a solution of haematin in alcohol which has been acidified 

 with sulphuric acid and then heating. A method has been suggested 

 by Gosdew for recrystallizing haemin, but it is not recommended by 

 Hoppe-Seyler, as he found it to yield a mixture of haemin with 

 haematin. 



Haematoporphyrin. 



Mode of When haematin is thoroughly mixed with concentrated 



preparation. sulphuric acid, the substance dissolves, and, after filtering 

 through asbestos, a clear and beautifully purple-red solution is obtained. 

 When this solution is treated with a large quantity of water, the greater 

 part of the dissolved coloured body is precipitated in the form of a brown 

 flocculent precipitate, the quantity of which increases if alkalies be added so 

 as fully to neutralize the acid. In this operation the acid separates the 

 whole of the iron from the haematin, and it is found in the solution in the 

 state of a ferrous salt. In the process of decomposition of haematin by 

 sulphuric acid there is no evolution of hydrogen gas. 



Properties. The precipitate which is thrown down by water from 



the sulphuric acid solution is insoluble in concentrated solution of potassium 

 sulphate, but soluble in water, and the watery solution possesses the same 

 optical properties as the solution in sulphuric acid. It is also soluble in 

 alkaline leys, yielding solutions possessed of a reddish-brown colour ; in 

 undergoing solution the substance appears to undergo some decomposition. 



Both the original sulphuric acid solution and the dilute alkaline solu- 

 tions of the body precipitated by water from it, possess characteristic and 

 different spectra. 



The first (solution in strong sulphuric acid) exhibits a pretty dark 

 band immediately below D, and a very sharply defined band nearly inter- 

 mediate between D and E. 



The second (.solution of precipitated body in alkaline leys) presents a 

 four-banded spectrum : to wit a weak band midway between C and D, an 

 equally weak band between D and E but nearer to the former, a more strongly 

 marked band nearer to E, and lastly a fourth band, darkest of all, which 

 is not however very sharply defined, and extends through. -fths of the 

 space beween b and F. 



To this iron-free body, obtained from haematin by the action of strong 

 sulphuric acid, Hoppe-Seyler attaches provisionally the term of Haemato- 

 porphyrin, and ascribes the formula C^H^NgO^. 



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