316 THE BLOOD. 



that is, amounts which could scarcely be owing to technical 

 errors. 



Serum-albumin. Serum-albumin is found in the plasma, the 

 serum, the lymph, in exudates and transudates, and under certain 

 pathological conditions also in the urine, where it usually occurs in 

 association with serum-globulin. It is most conveniently obtained 

 from blood-serum after removal of the serum-globulin by saturation 

 with magnesium sulphate at a temperature of 30 C. The filtrate is 

 saturated with sodium sulphate or ammonium sulphate at 40 C., or 

 treated with acetic acid, so that the solution contains about 1 per 

 cent. In either case the precipitated serum -albumin is filtered off, 

 pressed between layers of filter-paper, dissolved in water (the reac- 

 tion should be neutral), and separated from the remaining salt by 

 dialysis. From its aqueous solutions it is finally obtained by 

 evaporation at a low temperature or by precipitation with alcohol, 

 which must be rapidly removed, however, as otherwise it will cause 

 coagulation of the albumin. 



In the dry state serum-albumin is a transparent, gum-like, brittle, 

 hygroscopic mass, or a white powder, which can be heated to 100 C. 

 without undergoing decomposition. Solutions of the pure substance 

 in distilled w^ater coagulate at 50 C., while in the presence of salts 

 a higher temperature is necessary. This varies with the amount of 

 salt present, as also with the concentration of the albumin. A 1 

 to 2 per cent, solution containing 5 per cent, of sodium chloride 

 coagulates between 75 and 90 C. From its salt solutions serum- 

 alhumin may be obtained in crystalline form. Its specific rotation 

 in distilled water varies between 62.6 'and 64.6 a [D], 



According to Halliburton, the serum-albumin of mammalian 

 blood-serum is not a single substance, but consists of three distinct 

 albumins, which he terms -, /9-, and ^-serum-albumin. They are 

 said to coagulate at 73 C., 77 C., and 84 C., respectively. In 

 cold-blooded animals, -serum-albumin only is said to occur. 



Separation of the Albumins of the Blood-plasma from Each 

 Other. To isolate the fibrinogen, the plasma is treated with an 

 equal volume of a saturated solution of sodium chloride. The result- 

 ing precipitate is filtered off and purified as described. The filtrate 

 contains serum-globulin and serum-albumin. The globulin is pre- 

 cipitated by saturation with magnesium sulphate, filtered off, and 

 likewise purified. The filtrate contains only the serum-albumin, 

 which may be obtained, as just described, by saturation with sodium 

 or ammonium sulphate. 



Quantitative Estimation of the Total Albumin of the Plasma. 

 The albumins are most conveniently estimated by treating a care- 

 fully measured and weighed amount of the plasma, after neutraliza- 

 tion with acetic acid, with five times its volume of alcohol. After 

 standing for twenty-four hours the solution is boiled for several 

 minutes, and the resulting precipitate collected on a weighed filter, 

 washed with, hot alcohol, then with ether, dried at 115 C., weighed, 



