52 INFLUENCE OF TEMPERATURE 



Instead of measuring the velocity of reaction by 

 means of determinations at arbitrary stages of the 

 reaction, we may also determine it by evaluating 

 the time which is necessary for reaching a certain 

 point of the process, for instance that at which 50 

 per cent of the original substance is transformed. It 

 is also sometimes possible to decide how long the 

 process takes to reach practically its end-value, as 

 is, for instance, done in the measurement on the 

 time of fermentation by JODLBAUER (cf. p. 60). 

 This method has also been used in MADSEN'S ex- 

 periments on the digestion of gelatine, where he 

 determined how long it took for a certain quantity 

 of pepsin or trypsin or another proteolytic ferment 

 to liquefy the jelly. An analogous case is also the 

 observation of the time necessary for clotting milk 

 by means of rennet. In the same manner we 

 determine the time for total haemolysis or total 

 bacteriolysis, when all bacteria are killed. 



In these cases the velocity of reaction is inversely 

 proportional to the time necessary for the reaction. 

 In this manner GROS determined the time necessary 

 for total haemolysis in hot water at different temper- 

 atures. His determinations give a value /I = 63,700. 

 I have repeated these determinations over a greater 

 interval of temperature. I found the following 

 values : 



Temperature ( C.) . 50-6 54-3 58-2 



Time (minutes) . 570 188 57 ^=64,200. 



The logarithms of these times are plotted in the 

 following diagram (Fig. n), which gives a very 



