APPENDIX. 



AN ACID TEST OF CREAM. 



EXTRACTS FROM ILLINOIS EXPERIMENT STATION "BULLE- 

 TIN NO. 32," BY E. H. FARRINGTON, M. S. 



The sourness of cream is one of the things considered by 

 many dairymen in making butter. They may not agree on 

 the amount of acidity that cream should have when it is 

 ready for churning, but many base their judgment on the 

 taste or appearance of the cream. 



The first record of a measurement of the acidity of cream 

 before churning, so far as known to the writer, was reported 

 in 1887 by John Sebelein, in "Versuchs-Stationen," XXXIV, 

 p. 94. He used an alkaline liquid of known strength (one- 

 tenth normal) and by adding a few drops of a liquid indicator, 

 phenolphtalein, to a measured quantity of cream (50 c. c., or 

 about one- tenth of a pint,) the amount of acid in the cream 

 was estimated by measuring the quantity of the alkaline 

 liquid that it was necessary to add to the 50 c. c. of cream in 

 order to produce a pink color in the cream tested. The in- 

 dicator, phenolphtalein, has the property of causing a pink 

 color in some alkaline liquids, but does not change the color 

 of acid solutions. This gives a means of measuring the 

 amount of acid in milk or cream by noting the quantity of an 

 alkaline liquid of known strength that will produce this pink 

 color in a measured amount of cream. The strength of the 

 alkaline liquid and the amount of cream taken for each test 

 are constant, known quantities, always the same in compara- 

 tive trials of different lots of cream. The amount of acid in 

 the measured quantity of cream is unknown until, by testing 

 it, it is observed how much of the standard alkaline liquid it 

 17 (257) 



