206 HEMOGLOBIN. 



determining the water of crystallisation of the blood-colouring matter 

 are surpassed by those attending the estimation of its solubility. It is 

 doubtless in some measure due to the difficulty, almost the impossibility, 

 of eliminating every trace of certain of the reagents (especially the 

 alcohol), employed in the preparation of the body, that any attempts 

 to determine with precision the solubility of oxyhsemoglobin have 

 failed. The chief cause of the discrepancies between the observations 

 of different observers is, however, probably that they were unaware 

 of the physical, and perhaps also chemical, changes which haemoglobin 

 undergoes in the process of recrystallisation. 



The oxyhaamoglobin of all birds, of the ox, of the pig, and of man 

 is distinguished by its great solubility, the relative solubility increasing 

 in the above order. Next in order of solubility comes the haemoglobin 

 of the horse, dog, squirrel, guinea-pig, and rat, the latter being certainly 

 the least soluble. 



According to C. Schmidt, 100 grms. of water at 18 C. dissolve 15 '59 grms. 

 of the crystallised oxyhsemoglobin of the dog. From the fact that the oxy- 

 hsemoglobin analysed by C. Schmidt when ignited yielded on an average 0'91 

 per cent, of P 2 5 , we are in a position to state that the body he experimented 

 with was very impure, and consequently that his estimate of its solubility in 

 water possesses no value. Hoppe-Seyler found that 100 c.c. of water at 

 5 C. dissolved 2 grms. of the dry oxyhsemoglobin of the dog. 



Lehmann found that one part of the dry crystallised oxyhsemoglobin of 

 the guinea-pig required 597 parts of water to dissolve it, but the temperature 

 at which the determination was made is not stated ; l moreover, it is more 

 than doubtful whether the substance experimented with was pure. 



The present state of our knowledge permits us, therefore, to state 

 that the oxyheemoglobin of different animals differs in no property so 

 remarkably as in its solubility in water. It appears, further, that oxy- 

 haemoglobin which, according to the more recent researches, contains 

 the same percentage of iron (that of the horse, ox, dog, and pig), and 

 therefore presumably possesses the same molecular weight, and which, 

 further, crystallises in the same manner exhibits marked differences in 

 solubility. As the oxyhaemoglobins of the horse and of the dog seem, 

 in so far as the water of crystallisation is concerned, to be identical, 

 and as the researches of Hiifner and his school have proved the identity 

 of the iron-containing part of the molecule in the haemoglobin from the 

 most different animals, we are, it appears to me, driven to the con- 

 clusion that the difference in solubility must le due to differences in 

 the albuminous residue in the haemoglobin molecule. 



Solubility in liquids other than water. Oxyhaemoglobin is soluble in 

 highly diluted solutions of ammonia, and the other caustic alkalies, and 

 their carbonates. These solutions resist decomposition much longer 

 than aqueous solutions of haemoglobin. 2 Kiihne states that a highly 

 dilute ammoniacal solution of oxyhamioglobin will remain in great part 

 unchanged for several weeks at ordinary temperatures. Stronger 

 solutions of the caustic alkalies or their carbonates induce decom- 



1 W. Preyer, "Die Blutkrystalle, " S. 55. 



2 Based upon these facts is the method, introduced by Hiifner, of diluting blood or 

 solutions of oxyhsemoglobin with solutions containing O'l per cent, of NaOH. Such 

 solutions are much more transparent than purely aqueous solutions, and are therefore 

 most valuable for the purposes of spectroscopic researches. 



