SOME PHYSICO-CHEMICAL MEASUREMENTS ON MILK. 177 



The close agreement in the majority of cases between 

 observed and calculated results, shows, that a relation does 

 exist between the viscosity and the solids of a milk, and 

 that this relation is a function of the fat aud of the solids 

 not fat, rather than of the total solids. 



Change of Viscosity with Increase of Temperature. 



On heating, the viscosity of a milk rapidly decreases* 

 such decrease being approximately 4*5 per cent, between 

 20° and 30° C. In order to obtain a relationship between 

 the viscosity and the temperature, the viscosities given in 

 Table III were obtained for a sample of milk. 



Table III. 

 Temperature ° 0. Viscosity. 



20 2*100 



25 2*034 



30 1*987 



By substituting these values for n and nt in Poiseuille's 

 formula, 



_ n 



1H ~ 1 + at + /3t 2 

 where n is the viscosity at 0° O.and m the viscosity at t°, 

 the values of the constants a and /3 were found to be 

 « = '00723 p = - '000156 



In Table IV are given the values, for a number of milks 



at a temperature of 40° 0., of the observed viscosities and 



also of the viscosities calculated by means of the above 



formula. 



Table IV. 



tt- -j. oa° r\ Viscosity 40° C. Viscosity 40° C. 

 Viscosity 20 C. . , . Jx / i i * j\ 



J (observed). (calculated). 



2*006 1-853 1*853 



2-029 1*870 1-875 



1*951 1-800 1-802 



1*984 1*834 1*833 



1*992 1*845 1*840 



L— November 5, 1913. 



