25 



It is not necessary to use quite the full amount of acid when test- 

 ing whey. 



The ordinary milk bottle is not suitable for testing skim-milk, 

 buttermilk, or whey, as it is almost impossible to make an accurate 

 reading of such a small amount of fat when it is extended over a broad 

 surface. 



The Lactometer and the Detection of Adulterations in Milk. 



The lactometer is an instrument used to determine the specific grav- 

 ity of milk. The term specific gravity means the weight of a certain 

 volume of any substance compared with the weight of the same volume 

 of pure water at a standard temperature. 



There are different kinds of lactometers, but the Quevenne is the 

 most suitable for milk-testing. By means of it we can determine rapidly 

 the relative weight of milk and water. 



The Quevenne lactometer is standardized at a temperature of 60 de- 

 grees ; if the milk to be tested varies from this, corrections may be made 

 according to the following rule.: For each degree in temperature above 

 60, add .1 ( j(7 ) to the lactometer reading, and for each degree below 

 60, subtract .1 ( jj jfrom the lactometer reading. This rule is practical- 

 ly correct, if the temperature is kept within a range of from 50 to 70 

 degrees. It can be readily recalled when we remember that the density 

 of milk increases with a reduction of temperature and decreases with a 

 rise in temperature. The scale on the lactometer is graduated from 15 

 to 40, and indicates a specific gravity of from 1.015 to 1.0-10. 



A^ote. The correct lactometer reading (or L.R. at GO F.)H-1000h- 

 1000 indicates the specific gravity. 



The lactometer reading of whole milk usually ranges from 29 to 34, 

 although it may fall as low as 27, or go as high as 35. The lactometer 

 reading of skim-milk varies from 33 to 38. The reading should be taken 

 soon after placing the instrument in the milk ; if cream be allowed to rise 

 on the milk, the reading wiM be too high, as the bulb of the lactometer 

 will be floating in partially skimmed milk. Milk should be cooled and 

 allowed to stand some time (1 to 3 hours) after being milked before tak- 

 ing the lactometer reading. Otherwise the readings will be too low. 



The composition of milk is about as follows : 



Fat 3.6 per cent. 



Casein 2.5 '' '' ^ solid.s 



Albumen 7 " " {,q l 



Sugar r>.\f I f^^^ 



Ash •■• -7 



Water • S7.5 " " 



100.00 



4— Bull. 143 



