90 PROPERTIES OF OXY-HAEMOGLOB1N. [BOOK I. 



oxy-haemoglobin of the- guinea-pig crystallizes in the form of tetra- 

 hedra or of tetrahedra with truncated edges and angles, which were 

 at one time supposed to belong to the regular system ; they have been 

 proved by Lang 1 to belong to the rhombic system. 



Crystals of oxy-haemoglobin, of whatever form, are doubly re- 

 fracting and pleochromatic ; when examined in polarized light the 

 crystals, according to the position of their axes in reference to the 

 observer, appear of a dark reddish-blue or of a bright scarlet 

 colour. 



Certain Oxy-haemoglobin, as obtained by any of the pro- 



chemical cesses above described, presents when moist the appear- 



reactions of ance of a pasty mass of a cinnabar-red colour ; it may be 

 oxy-haemo- dried in vacuo over sulphuric acid at temperatures 

 giobin. below C. without undergoing decomposition, and the 



dried crystals thus obtained are found to be perfectly soluble in 

 water, yielding a solution which presents the optical properties after- 

 wards to be described. The crystals of oxy-haemoglobin dried in 

 vacuo still retain 3 or 4 per cent, of water of crystallization, which is 

 driven off by heating to 110 or 120 C. If the crystals of oxy-haemo- 

 globin have been thoroughly dried at a temperature below C., the 

 dried substance may be heated to 100 without undergoing decom- 

 position; the slightest trace of moisture suffices, however, to effect 

 decomposition at much lower temperatures a decomposition evidenced 

 by the assumption of a brown colour, by the substance becoming in- 

 completely soluble in water, and by a modification of the optical pro- 

 perties (formation of methaemoglobin). 



Solutions of oxy-haemoglobin in distilled water if sealed in vessels 

 with no perceptible air-space may be kept for many months, or perhaps 

 years, without undergoing any further change than the reduction or 

 loss of oxygen to be afterwards referred to. The fact is one of 

 importance practically, as enabling standard solutions of haemoglobin 

 to be preserved almost indefinitely 2 . 



Oxy-haemoglobin obtained from different animals differs in its 

 solubility. That obtained from the guinea-pig is comparatively little 

 soluble, whilst that of bullock's and pig's blood is very soluble. 

 Gautier gives the following order of solubility of the haemoglobin 

 obtained from several animals cat, dog, horse, man : the degree of 

 solubility increasing according to the order named. 



Haemoglobin is readily soluble without decomposition in very 

 weak solutions of the caustic alkalies or of the corresponding 

 carbonates; an excess of alkali, however, very readily induces de- 

 composition. 



All acids and salts having an acid reaction decompose haemoglobin 

 with the formation of haematin. 



1 Sitzungsber. d. Wiener Akad. Vol. XLVI., p. 85. 



a Hoppe-Seyler, " Weitere Mittheilungen iiber die Eigenschaften des Blutfarbstoffs. 

 2. Ueber die Fahigkeit des Hamoglobins der Faulniss sowie der Einwirkung des 

 Pankreasferments zu widerstehen. " Zei tschrift f. physiol. Chem., p. 125, et seq. 



