GELATIN 51 



11. Gelatin and Deaminized Gelatin. — The only practicable 

 method of purifying gelatin which has been devised consists in 

 subjecting the best quahties of commercial gelatin to very pro- 

 longed dialysis against running distilled water (4). Deaminized 

 gelatin is prepared by Blasel and Matula (1) by the following 

 method : 



About 200 grams of the best commercial gelatin is dissolved 

 in one litre of warm water. To this solution is added 200 grams 

 of sodium nitrite dissolved in one litre of water. After cooling, 

 140 grams of glacial acetic acid is carefully added. The mix- 

 ture is allowed to stand for twelve hours and then heated on 

 a water-bath for two hours. The deaminized gelatin is then 

 precipitated by the addition of solid ammonium sulphate and 

 purified by prolonged dialysis (2 weeks) against running distilled 

 water. 



12. Globin. — Globin inay best be prepared by the following 

 modification of the method devised by Schuiz (39) (37). 



A thick suspension of ox-corpuscles is obtained by centrif- 

 ugalizing freshly defibrinated ox-blood, the volume of the sus- 

 pension being about one-third that of the blood from which it 

 is derived. 



After pipetting off the supernatant serum the suspension is 

 diluted to the original volume of the blood from which it was 

 derived by the addition of N/Q NaCl solution and the centrif- 

 ugalization is repeated, the supernatant fluid being removed as 

 before. This is repeated six times in order to free the corpuscles 

 from adherent serum. After the last centrifugalization the cor- 

 puscle suspension is not again diluted with NaCl. 



The thick suspension of corpuscles which is thus obtained is 

 diluted to ten times its volume by the addition of distilled water. 

 The corpuscles are thus "laked" and the contained haemoglobin 

 is discharged into the water, forming a clear solution which is 

 allowed to stand in tall glass vessels for twenty-four hours in 

 order to permit the leucocytes to settle. The upper portion of 

 the fluid is then decanted and employed, the lower portion of 

 the fluid being rejected. 



Two and one-half litre portions of this fluid are placed in six- 

 litre bottles, to the contents of each bottle are added 56 cc. of 

 concentrated HCl (sp. gr. 1.18) and the mixture is thoroughly 

 shaken and allowed to stand at room temperature for one hour. 



