go MODERN METHODS OF TESTING MILK 



be used at higher temperatures and more at lower 

 (P. 43). 



It is the custom of many, when using less than 18 

 grams of cream, to add enough water to make the 

 volume about 18 cc., mixing well before adding the 

 acid. This calls for a larger amount of acid, of course, 

 than when no water is added to the cream, because the 

 water weakens the acid. 



Addition of water after whirling. A cleaner col- 

 umn of fat is usually obtained by adding water twice 

 after the first whirling, as in the case of testing milk 

 (p. 64). With a single addition of water, the lower 

 line of the fat-column is cloudy-looking and uneven 

 and indistinct, while the liquid below is milky. This 

 condition may often be remedied by placing the bottles 

 in water at 130 to 140 F. for 15 or 20 minutes be- 

 fore a final whirling, or, if this fails, the fat can be 

 solidified by placing the bottles in cold water after the 

 last whirling and then heated to 130 or 140 F. be- 

 fore reading. 



Control of -meniscus in reading fat-column, There 

 has been much inaccuracy introduced into the testing 

 of cream by the variable factor of the meniscus in the 

 fat-column ; the details of the trouble need not be dis- 

 cussed here. The only reliable method of removing 

 this source of inaccuracy is to get rid of the meniscus, 

 changing the upper curved surface of the fat-column 

 into a flat surface. This can be accomplished by the 

 use of several agents, among which are (i) glymol, 

 (2) amyl alcohol and (3) alcohol saturated with fat. 

 When any one of these solutions is placed on top of the 

 fat-column, it keeps separated from the fat but re- 



