PRELIMINARY AND MINOR PAPERS 



STUDIES IN THE EXPANSION OF MILK AND CREAM 



By H. W. Bearce,' 

 Assistant Physicist, Bureau of Standards, Dep'artynent of Commerce 



[A report on a series of experiments conducted for the Dairy Division, Bureau of Animal Industry! 



INTRODUCTION 



On May 27, 191 3, the Dairy Division of the Bureau of Animal 

 Industry requested the Bureau of Standards to determine the coefficient 

 of expansion of market milk, single cream, and double cream. It was 

 thought that the examination of a few samples of each would be suffi- 

 cient to serve the purpose. Subsequent observations, however, showed 

 that this was not the case. The wide variation of the rate of expansion 

 of the samples first examined made it apparent that a much greater 

 number of samples would be required than had been anticipated. The 

 results here published are therefore the outgrowth of what was originally 

 expected to be only a very few determinations. 



OBJECT OF THE WORK 



The principal object in undertaking the work was to determine the 

 change in volume which occurs when the temperature of a given volume 

 of milk or cream is changed and from the rate of change of volume to 

 construct a table of relative volumes of milk and cream at various 

 temperatures. For example, when milk is pasteurized and put into 

 containers at a high temperature, it is sometimes desirable to know 

 what volume of milk must be measured out at that temperature, in order 

 that it may occupy a required volume at some standard temperature. 



In the enforcement of the pure food and drugs laws by the Bureau 

 of Chemistry it is held that a container shall have its full nominal capacity 

 at 20° C. (68° F.) — that is, a container labeled as holding i gallon must 

 hold 231 cubic inches at 20° C. For the sake of uniformity and also 

 because 20° C. is a reasonable and convenient temperature, it has been 

 chosen as the basis of the table of volumes of milk and cream published 

 herewith. The samples of cream submitted by the Dairy Division 

 were prepared from mixed herd milk produced at the Dairy Division 

 Experiment Farm, Beltsville, Md. The percentage of fat was deter- 

 mined in each case by the Babcock test, and the samples are believed 

 to be normal cream for the stated percentages of fat.^ 



METHOD OF DETERMINATION 



The principle employed in determining the rate of expansion was to 

 measure the change of density with change of temperature and from 

 that to calculate the change in volume. 



* Tlie author would acknowledge his indebtedness to Miss Alice Purinton, formerly of the Bureau of 

 Standards, and to Mr. E. L. Pe^er for assistance rendered in the work. 



' These samples were prepared and the fat determinations made by Mr. R. H. Shaw, of the Dairy 

 Division. 



.Toumal of Afn-iruUiual Research, Vol. III. No. 



Dept. of AKricuIture, Washington, D. C. Dec. is. 1914 



(251) A-ii 



