192 H. B. TAYLOR. 



necessity for all vessels containing milk to be kept covered, 

 as pathogenic bacteria carried around on the dust particles 

 are just as likely to fall into milk as the harmless bacilli 

 producing lactic acid. 



Summary. 



1. The viscosity of milk is related to the percentage of 

 fat and to the solids other than fat in the milk. A formula 

 was derived which permitted the calculation of "solids not 

 fat" from a determination of the viscosity, and the fat of 

 milk. The viscosity of milk decreases with rise of tem- 

 perature in a regular way from 20 to 40° O. which can be 

 expressed by means of the usual equation 



_ no 



^ ~ 1 + at + fit 2 * 



Apart from the general decrease in viscosity, milk which 

 has been heated from 20° O. to any temperature up to 60°C. 

 is found to have decreased in viscosity, when brought back 

 to the origiuai temperature 20° O. Milk heated to 70° O. 

 and recooled is found to have increased in viscosity. 



2. The electrical conductivity of milk is due to the solids 

 other than fat, the action of the fat globules being to lower 

 the conductivity. 



3. The H ion concentration of normal fresh milk is 10~ 6 " 8 

 and after the milk has soured the concentration is 10~ 4 ' 65 ; 

 these values did not vary to any great extent from one 

 cow to another in a considerable number of samples. 



4. It is shown that the decomposition of milk which has 

 stood 24 hours is most rapid on the days when the operation 

 of milking has been conducted with a strong dusty wind 

 blowing. 



These investigations were carried out in the Chemical 

 Laboratory of the University of Sydney, and I wish to 

 express my thanks to Professor Fawsitt for his advice 

 throughout the work. 



