HEAT, LIGHT AND PRESSURE 305 



coagulation have been discussed at some length in Chap. VI, and 

 it has been pointed out in that chapter, and incidentally, in 

 Section 1 of this chapter that the application of heat to proteins 

 in solution results, probably, not only in the abstraction of the 

 elements of water from the protein, with the formation of anhyd- 

 rides, but also in its polymerization. 



Under definite conditions of concentration, reaction and salt- 

 content of its solution, etc., the coagulation-temperature of * a 

 protein is tolerably constant, and Fredericque (27), Halliburton 

 (29) and others have utilized this, property very extensively in 

 the endeavor to separate and characterize different proteins. 



The concentration of protein, and especially the presence of 

 other substances in the solution, very markedly modifies the 

 coagulation-temperature, however. The influence of inorganic 

 salts, upon the "temperature of coagulation" has been inci- 

 dentally discussed in Chap. VI. The influence of a variety 

 of salts in acid and alkaline solutions upon the coagulation- 

 temperature of proteins has been very extensively studied by 

 Pauli and his pupils (32), and found to be in satisfactory accord- 

 ance with the view that heat-coagulation, like salt- or alcohol- 

 coagulation is accomplished through the dehydration of the 

 protein molecules. 



The very important observation has been made by Chick 

 and Martin (17) that the heat-coagulation of haemoglobin and 

 egg albumin (in solutions of crystallized preparations of these 

 substances) is not an instantaneous process, but that it proceeds 

 with a definite velocity which decreases as the protein becomes 

 coagulated and increases very markedly with rise in temperature. 

 The relation between time of exposure to a temperature suffi- 

 cient to bring about coagulation and the quantity of protein 

 coagulated is, for haemoglobin, that which is characteristic for 

 the occurrence of a monomolecular chemical reaction, namely: 



log ^ = Ktt 



Lt 



where C is the initial concentration of the substance (protein), 

 C t its concentration at time t and K is a constant (the velocity- 

 constant of the reaction). The following are illustrative of their 

 results : 



