70 PHYSIOLOGICAL CHEMISTRY. 



HUFNER as 1.582 c. c. (at C. and 760 m.m. Hg). The ability 

 of haemoglobin to take up oxygen seems to be a function of the iron 

 it contains, and when this is calculated as about 0.33-0.40$, then 

 1 atom of iron in the haemoglobin corresponds to about 2 atoms = 1 

 molecule of oxygen. The combination of haemoglobin with oxygen 

 is, as has been stated, loose and dissociatable, and the quantity 

 of oxygen taken up by a haemoglobin solution depends upon the 

 pressure of the oxygen at that temperature. If this latter be 

 decreased by means of a vacuum, especially on gently heating or 

 by passing some indifferent gas through the solution, all of the 

 oxygen may be expelled from an oxyhaemoglobin solution so that 

 only haemoglobin remains. The reverse of this is true of a haemo- 

 globin solution which by its remarkable attraction for oxygen may 

 be converted into oxyhaemoglobin. Oxyhaemoglobin is generally 

 considered as a weak acid. 



Oxyhaemoglobin has been obtained in crystals from several 

 varieties of blood. These crystals, first observed by REICHERT 

 and FUNKE, are blood-red, transparent, silky, and may be 2-3 m.m. 

 long. The oxyhaemoglobin from squirrel's blood crystallizes in six- 

 sided plates of the hexagonal system; the other varieties of blood 

 yield needles, prisms, tetrahedra, or plates which belong to the 

 rhombic system. The quantity of water of crystallization varies 

 between 3-10$ for the different oxyhaemoglobins. When com- 

 pletely dried at a low temperature over sulphuric acid the crys- 

 tals may be heated to 110-115 C. without decomposing. At 

 higher temperatures, somewhat above 160 C., they decompose, 

 giving an odor of burnt horn, and leave, after complete combus- 

 tion, an ash consisting of oxide of iron. The oxyhaemoglobin 

 crystals from difncultly-crystallizable kinds of blood, for exam- 

 ple from such as ox's, human, and pig's blood, are easily soluble in 

 water. The oxyhaemoglobin from easily- crystallizable blood, as 

 from that of the horse, dog, squirrel, and guinea-pig, are soluble 

 with difficulty in the order above given. The oxyhaemoglobin 

 dissolves more easily in a very dilute solution of alkali carbonate 

 than in pure water, and this solution may be kept. The presence 

 of a little too much alkali causes the oxyhaemoglobin to quickly 

 decompose. The crystals are insoluble without decolorization 

 in absolute alcohol. According to NENCKI, it is converted 



