8 



Testing Milk and Its Products. 



Rochelle salts, sodium sulfate and sodium hydroxid. 1 150 cc. of this 

 mixture of salts are dissolved in 1 liter of water. In testing milk, 

 11 cc. of this solution and 0.6 cc. of "sinol" (isobutylalcohol) are 

 added to 10 cc. of milk. After thorough mixing of the milk and 

 solution the test bottles are placed in water of 113 F. for 3-5 

 minutes, when they are shaken till all the curd dissolves. They 

 are then revolved in a centrifuge for 3 minutes and the results read 

 off. By heating the bottles for 1 hour in boiling hot water correct 

 results may be obtained without the use of a centrifuge. The 

 main advantages of the method appear to lie in this fact and in 

 that the use of a corrosive acid is avoided. 



12. The Lactocrite was one of the earliest practical milk 

 tests introduced. It was invented by De Laval in 1886. The 

 acids used in this test are lactic acid (originally, acetic acid) 

 with a mixture of hydrochloric and sulfuric acids. This test is 

 now but rarely met with. 



13. 



FIG. 2. De Laval's butyrometer. 

 In the De Laval butyrometer (fig. 2) the same acid is 



used as in the Babcock test, but the tubes employed and the 

 manipulations of the method differ materially from this test; a 

 smaller sample of milk is taken (only 2 cc.) and a correspond- 

 ingly small quantity of acid used. Where a large number of 



1 Barthel-Goodwin, Methods used In Examination of Milk and Dairy 

 Products, p. 77. 



