40 CHEMICAL STATICS 



tides,* and it neutralizes, to phenolphthalein and to litmus, exactly 

 the quantities of alkali determined by Soldner (41), Lacquer and 

 Sackur (15) and Van Slyke and Hart (45). 



Casein which has been carefully prepared in the manner out- 

 lined above, floats upon the top of and is not readily wetted by 

 water or watery solutions of bases; if, however, it contains a 

 mere trace of moisture, it is readily wetted by all save the most 

 alkaline solutions. In order to successfully and completely dis- 

 solve perfectly anhydrous casein it is necessary to first add to it 

 a very little of the solution in which it is to be dissolved, rub it 

 up into a paste, and then add, while stirring, the remainder of 

 the solution. 



If casein which is readily wetted by water be desired (34) it is 

 necessary to omit the desiccation over H 2 SO4. For this purpose 

 CaCl 2 should be employed as the desiccating agent, and desic- 

 cation should be continued for 12 hours at about 30 C. Casein 

 prepared in this way readily sinks in and is wetted by water and 

 aqueous solutions; it contains, however, not very significant traces 

 of moisture and a considerable amount of adherent ether. 



3. * Insoluble" Serum Globulin. There appear to be at 

 least two globulins in serum, the one insoluble in distilled water, 

 which is precipitated on dialysis of the serum, or dilution and the 

 subsequent addition of a weak acid; the other soluble in water, 

 precipitable by saturation with magnesium sulphate after the 

 removal of the insoluble fraction (16) (5) (27). 



According to Hardy these globulins differ markedly in their 

 phosphorus content, the insoluble globulin containing from 0.07 

 to 0.08 per cent phosphorus; the soluble globulin only a trace 

 (about 0.009 per cent) of phosphorus (9). 



According to Hammarsten (7) the individuality of these pro- 

 teins, and the freedom of any given preparation of the one from 

 an admixture of the other is open to serious doubt. Moreover, 

 as Taylor has shown (44), the "insoluble" globulin is readily 

 converted, by hydrolysis, into the "soluble" form. The relation- 

 ship between the various serum globulins would therefore appear 

 to be somewhat analogous to that between the various members 

 of the paranuclein group. . 



* So that when litmus paper is dipped into a suspension of casein particles 

 in distilled water the paper is reddened where it is touched by the undissolved 

 particles, while the fluid which bathes them remains clear and neutral (30). 



