188 H. B. TAYLOK. 



It will be seen from the following table that temperature 

 plays a large part in the rate at which the H ion concen- 

 tration of the milk increases, 



Table IX. 



Hours old. H ion at 30° C. H ion at 25° C. 



7*0 6*80 6*80 



11*0 6*60 6'65 



14*0 6*40 6*60 



17*5 5*30 5*50 



19'0 5*10 5*45 



21*0 4*80 5*35 



23*0 4*65 4'80 



24*5 4*65 4*70 



25*5 4*65 4*70 



30*5 4*65 4*65 



102*5 4*65 4*65 



At a temperature of 30° O. the maximum value for the 

 H ion was reached in 23 hours, at the temperature of 25°0. 

 it took 7*5 hour longer to gain the same figure. The period 

 lapsing between the time of milking the cow and the time 

 when acid began to be produced was on an average, at a 

 temperature of 30° C, about seven hours, and the form- 

 ation of acid continues until enough acid is formed to inhibit 

 the growth of the bacteria present, as shown by the constant 

 figure for the H ion at the bottom of the above table. 



Figure three gives a graphical representation of the 

 increase of the H ion along with the time in one sample 

 of milk. 



In the seventeen samples which were examined, the 

 average value for the H ion concentration of the fresh 

 sample was 6*83, one sample gave a value of 7*1 the 

 remainder varying from 6'7 to 6*9, these figures show that 

 in the majority of cases milk as received from the cow is 

 very slightly acid, this acidity being due to a slight excess 



