MANUAL OF GENEKAL AGEICULTUEE. 107 



79. TESTING THE ACIDITY OR SOURNESS OF 



MILK AND CREAM. 



Materials: Samples of milk and cream, 50 c.c. bu- 

 rette* provided with stopcock, 17.6 c.c. pipette, a tin, 

 porcelain or glass cup, % gallon neutralizer, indicator. 



With a 17.6 c.c. pipette measure into a clean cup this 

 amount of milk and add a few drops of indicator. Attach 

 the burette to a ring stand and fill with the alkali solu- 

 tion nearly to zero mark. Eead accurately the top of 

 the column. Next cautiously add the neutralizer from 

 the burette. By constant stirring during the operation 

 it will be noticed that the pink color formed by the addi- 

 tion of even a drop of alkali will at first entirely dis- 

 appear, but as more and more of the acid in the sample 

 becomes neutralized, the color will disappear more slowly, 

 until finally a point is reached when the pink color re- 

 mains permanent for a time. No more alkali should be 

 added after the first appearance of a uniform pink color 

 in the sample. Take a second reading of the column. 

 Ascertain the amount of alkali solution used by subtract- 

 ing the readings of the scale on the burette. The per 

 cent of acidity may be obtained by dividing the number 

 of c.c. used by 20. The result will be the per cent of 

 acidity in tenths. For example if 17.6 c.c. of milk re- 

 quired 3 c.c. of alkali solution to give a pink color the 

 per cent of acid is 8-^20= .4%. 



80. CALCULATION OF THE PERCENTAGE OF 



MILK SOLIDS. 



Materials : One or two pint samples of milk, cylinder, 

 lacometer, Babcock tester and accompanying materials. 



The calculation of milk solids can be easily done by 

 using the following formulas : 



Per cent of Solids not fat=%L+.2f. 



Per cent of Total Solids=H4L+1.2f. 



*In the Marshall Acid Test the per cent acidity can be read 

 directly. If no burette is at hand the outfit for this test had 

 better be purchased. 



