282 REPORTS ON THE STATE OF SCIENCE. 



former, the residual protein was determined colorimetrically ; and in 

 the case of the latter, by boiling a definite volume, and collecting, wash- 

 ing, drying, and weighing the precipitate. 



Hcemoglobin 3 per cent, solution. — Experiments were made at five 

 temperatures between 60° and 70°'4 C. From the haemoglobin remain- 

 ing in solution in samples withdrawn after various intervals of time, 

 the velocity constant was calculated on the assumption that the rate of 

 reaction was merely dependent upon the concentration of unchanged 

 protein at any particular moment. 



t -t ( log Co ~ log C ) = lc ' 



In all cases the calculated and observed values were in excellent 

 agreement. There is, therefore, no doubt that in the case of this protein 

 the reaction, although multi-molecular, is one of the first order, and 

 that, water being in excess, it proceeds as if it were a unimolecular one. 



Egg albumen 1 per cent, solution. — Similar experiments with egg 

 albumen at temperatures between 69° and 76° 0. gave results such 

 that when residual concentrations were plotted against time they all 

 lay upon smoothed curves. An examination of the figures, however, 

 showed that the relation of residual concentration to time did not fol- 

 low the same simple logarithmic law as had obtained with haemoglobin. 

 In these experiments the value obtained for k was not constant, but 

 decreased progressively during the course of the experiments. 



A reason for this departure soon became apparent. The reaction 

 rate is sensitive to small changes in the hydrogen-ion concentrations, 

 and as, for reasons which will be discussed later, hydrogen-ion con- 

 centration diminishes during the course of coagulation, the pure effect 

 ."if the concentration of protein upon the reaction rate is obscured. 

 We ultimately eliminated this disturbing factor by conducting the 

 experiments in the presence of excess of a solid acid, which was only 

 slightly ionised in solution. This provided us with a reservoir of acid, 

 and maintained a constant acidity. For the purpose, we employed 

 boracic acid, which, at 56° C, afforded us a degree of acidity with 

 which we could work. 



Under these conditions the reaction proceeded logarithmically. 



Temperature and denaturalion. 



The effect of temperature upon the velocity of this reaction was 

 determined by comparing the velocity constants at various tempera- 

 tures. Only a comparatively small range could be studied (60° to 

 70°'4 for haemoglobin and 60° to 76° C. for egg albumen) owing to the 

 extraordinarily high temperature coefficient possessed by the reactions. 

 The results were in both cases in good agreement with the law of 

 Arrbenius. 



/2T () T„ K<A 

 '' = lT;-T n lo g K J' 



