2 o6 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 impossil >ility, 
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 oxyhemoglobin 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 oxyhemoglobin 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 gnus, of water at 18° C. dissolve 15 - 59 grnas. 
of the crystallised oxyhemoglobin of the dog. From the fact that the oxy- 
hemoglobin analysed by C. Schmidt when ignited yielded on an average - 91 
per cent, of P 2 5J 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 oxjdienioglobin of the dog. 
Lehmann found that one part of the dr}^ crystallised oxyhemoglobin of 
the guinea-pig required 597 parts of water to dissolve it, but the temperature 
at which the determination was made is not stated ; 1 moreover, it is more 
than doubtful whether the substance experimented with w r as pure. 
The present state of our knowledge permits us, therefore, to state 
that the oxyhemoglobin of different animals differs in no property so 
remarkably as in its solubility in water. It appears, further, that oxy- 
hemoglobin — 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 hi 
solubility. As the oxyhemoglobins 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 Htifner and his school have proved the identity 
of the iron-containing part of the molecule in the hemoglobin from the 
most different animals, we are, it appears to me, driven to the con- 
clusion that the difference in solubility must he due to differences in 
the albuminous residue in the hemoglobin molecule. 
Solubility in liquids other than water. — Oxyhemoglobin 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 hemoglobin. 2 Kuhne states that a highly 
dilute animoniacal solution of oxyhemoglobin 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 Htifner, of diluting blood or 
solutions of oxyhemoglobin with solutions containing O'l per cent, of XaOH. Such 
solutions are much more transparent than purely aqueous solutions, and are therefore 
most valuable for the purposes of spectroscopic researches. 
