284 REPORTS ON THE STATE OP SCIENCE. 



HC1, and a diminution of acidity results which will obviously be pro- 

 gressive. The acidity due to the dissociated carboxyl groups will also 

 diminish as the concentration of protein diminishes. 



Effect of neutral salts upon rate of denaturation. 



Experiments on the influence of neutral salts, NaCl + Am 2 So 4 , 

 upon the velocity with which denaturation takes place were made by 

 the method described above. 



The concentration of salts in the solution varied between -^ and 

 three times normal. The residual albumen after different times at 

 71° C. was determined in the various solutions and plotted against 

 time. Smooth curves were drawn through the observational points. 

 From the curves it appears that in a concentration of NaCl 

 equal to normal the rate was about -Jff an d m twice normal about ? |- - 

 of that in the control. The effect of Am 2 So 4 was somewhat less. 



The second phase of heat coagulation ; agglutination of the 

 denaturated particles. 



Unless the content of a protein solution as regards salts and acid be 

 adjusted within certain definite limits, before boiling, the denaturated 

 protein cannot be separated by filtration through paper. The solution 

 assumes a milky or opalescent appearance, but the particles exhibit 

 little or no tendency to agglutinate. Every grade of dispersion may be 

 prepared by suitable manipulation of acid and salt. For reasons which 

 will appear in the sequel, denaturated serum proteins aggregate less 

 readily than egg proteins. 



The effect of various acids on the aggregation of particles of 

 denaturated serum proteins. 



Known volumes of solutions containing about 0'3 per cent, of serum 



N 

 proteins and varying amounts of y— z hydrochloric, acetic, or butyric 



acid were boiled and filtered through paper. In the event of any pre- 

 cipitate being caught by the paper this was washed, dried, and weighed. 

 By this means the amount of denaturated protein sufficiently aggre- 

 gated to be removed by a filter-paper was ascertained. 



The results showed that until a particular addition of acid (which 

 was the same for the three), had been made, no protein was held 

 back by the filter-paper. At a higher concentration of all three acids 

 complete agglutination occurred so that the filtrate was proteid free. 

 Complete agglutination was also maintained in those samples to which 

 a little more acid had been added, but was partial or did not occur in 

 the samples to which still more acid had been added. There was a 

 striking difference in the maximal amounts of the different acids after 

 the addition of which complete separation of the protein could be 

 effected. Excess of hydrochloric suspended agglutination more readily 

 than excess of acetic, and excess of acetic acid more readily than excess 

 of butyric. 



