612 EXPERIMENT STATION RECORD. 



analysis yielded glucose, levnlose, and arabinose 7.42 per cent, saccharose 

 2.93 per cent, galactan, araban, etc., soluble in 0.06 per cent NaOH, 3.73 per 

 cent, free organic acids 0.67 per cent, compounds of an acid nature, as salts, 

 8.43 per cent, and galactan, araban, etc., insoluble in alkali but bydrolizable by 

 dilute sulphuric acid (by difference), 23.2 per cent. 



On the heat coag'ulation of proteins, Harriet Chick and C. J. Martin 

 {Jour. Physiol., J,0 (1910), No. 5, pp. ^-.^30, figs. 7).— "The process of 'heat 

 coagulation ' has been studied with solutions of crystallized hemoglobin and 

 crystallized egg albumin. The complete solubility of both protelds after ex- 

 posure to dry heat at high tempei-atures (110 to 130° C. ) indicates that 'heat 

 coagulation ' of protein solutions is not a pure temperature effect, but a reaction 

 lietween water and protein. In the case of solutions of hemoglobin the rate of 

 coagulation at any moment is proportional to the concentration of residual 

 hemoglobin, i. e., it is a reaction of the first order. Coagulation of solutions of 

 egg albumin crystals is also an orderly time process, but the rate decreases 

 more i-apidly as coagulation proceeds than can be accounted for by the decrease 

 In concentration of uncoagulated protein. The explanation of this increased com- 

 plexity is attributed to want of homogeneity in the composition of egg albumin 

 crystals, and to the changing conditions due to the absorption of free acid by the 

 coagulum as formed. 



" The conclusion of Osborne that egg albumin crystals as prepared by Hop- 

 kin's method consist of salts of protein with the acids used in their preparation 

 is confirmed. In the case of 1 per cent solutions of egg albumin, twice recrystal- 

 lized from ammonium sulphate solution, the combined acid was equal to 0.0004 

 etpiivalents per gram of protein and the proportion of acid free was 0.7 per cent 

 of the total (0.0000251 N). On addition of alkali to the original solution most 

 was employed in decomposition of the acid protein salts, and diminution of the 

 free acid was Aery gradual. . . . 



" The effect of acid upon coagulation rare is considerable. The addition to a 

 solution of egg albumin crystals of 4 cc. tenth-normal alkali per gram protein 

 (i. e., the amount necessary to neutralize) reduced the reaction rate to one- 

 sixtieth. The influence of acid in accelerating the coagulation rate of a neutral 

 solution of egg albumin is at first relatively small : with each successive addition 

 of acid its influence becomes disproportionately greater. The mean coagulation 

 rate of egg albumin is not directly jiroportional to the hydrogen ion concentra- 

 tion. The velocity of the reaction increases at first more slowly and subse- 

 quently more quickly than the hydrogen ion content. It is possible, however, 

 that hydrogen ion concentration may be a factor in determining reaction rate. 

 As, however, most of the acid added combines to form salts, it may be that the 

 whole or part of its effect upon reaction rate is due to such salts reacting with 

 water more rapidly than protein itself and the more acid salts more rapidly than 

 the less acid salts. The free acid in a solution of egg albumin crystals dimin- 

 ishes and even disappears as coagulation proceeds. The quantity of free acid 

 fixed by the coagulation of a definite quantity of protein is at first nearly 

 jn'oportional to the concentration of free acid; as this concentration increases, 

 the amount fixed falls more and more short of proportionality. The curve suggests 

 that the phenomenon is one of absorption by the coagulated particles, as protein 

 already coagulated and washed absorbs free acid from solutions in which it is 

 suspended. 



" Coagulation of both proteins is influenced by temperature in accordance 

 with the law of Arrheuius or some similar logarithmic law. The temperature 

 coeflicient is exceedingly high, viz. 1.91 per degi'ee centigrade for egg albumin 

 and 1.3 per degree for hemoglobin." 



