196 W. D. HALLIBURTON. 



ties. It was heated to 100° C. in a water oven, and again 

 examined. It had lost but a slight amount of weight. It was 

 rather more insoluble in warm water than previously, but the 

 spectroscopic properties, and the form of the crystals obtained 

 from the solution, remained as before. This confirms the obser- 

 vation previously made by Hoppe-Seyler that dry haemoglobin 

 is not decomposed by a temperature of 100° C. It was again 

 heated in the water oven at 100° C. until there was no further 

 loss of weight. It was then heated to 120° C. in an air-bath, 

 and again examined. It was found to have lost considerably 

 in weight, to have lost its crystalline lustre, to be brown in 

 colour (hsematin) and to be insoluble in water. That is, it 

 parts with its water of crystallisation at a temperature which 

 decomposes it, with the formation of haematin, the proteid 

 matter becoming at the same time coagulated and insoluble. 



Experiments were then tried with the object of ascertaining 

 whether a lower temperature will remove the water of crystal- 

 lisation in a Torricellian vacuum. This I did by means of a 

 Pfliiger's mercurial air-pump. The action of the vacuum alone 

 converted the dried haemoglobin, at any rate partially, into the 

 conditions of methaemoglobin. The water of crystallisation 

 seemed to be completely lost at a temperature of 50° — 60° C, 

 as subsequent heating to 120° C. produced no further loss of 

 weight. But this temperature was also sufficiently high to 

 decompose the haemoglobin in such a way as to render it 

 insoluble, or almost so, in water, and therefore no crystals could 

 be subsequently obtained from it. 



The next method adopted was to convert the haemoglobin by 

 various reagents into methaemoglobin ; then by reducing agents 

 to form once more haemoglobin, and then obtain crystals of 

 this. But the reducing agents used were found to hinder the 

 formation of crystals. 



The third and simplest method was to repeatedly recrystallise 

 the haemoglobin, when it was found after three or four re- 

 crystallisations that no six-sided crystals were obtained, but a 

 mixture of rhombic needles and tetrahedra, and in some cases 

 the latter were absent. This is interesting; in connection with 



