13 



TABLE OP CORRECTIONS. 



In carrying out this test the following sources of error should 

 be avoided : (1) Sour cream ; (2) use of wet pipettes or flasks 

 when first measuring out the cream ; (3) careless mixing, where- 

 by air bubbles are drawn into the pipette along with the 

 cream ; (4) drawing the cream too far above the mark in the 

 pipette ; (5) loss of fat when adding water for dilution ; (6) im- 

 perfect mixing of the diluted cream ; (7) fine particles of fat left 

 on the pipette when the diluted cream is run into the test bottle ; 

 (8) reading the results at too low or too high a temperature. 



CLEANING THE TEST BOTTLES. 



A capable manager may often be known by the state in which 

 he leaves the testing room after the day's work : his bottles are 

 carefully washed and put away, every piece of apparatus is 

 clean and in its proper place, his working bench is free from 

 dirt or from liquids spilt during testing, and the centrifuge is 

 cleaned and carefully wiped dry. On the other hand, the 

 manager who leaves everything uncleaned or in a half-cleaned 

 condition, bottles greasy, corks unwashed or wet, reagents out 

 of place and the bench sloppy, is utterly unworthy of his posi- 

 tion, and it is not possible that the milk suppliers can receive 

 justice if they are paid on his figures. 



Test bottles, to be thoroughly cleaned, should be emptied 

 while the contents are hot, and to secure this they should be 

 kept, stopper end up, in the hot-water bath after reading at the 

 close of a test. Before emptying they should be vigorously 

 shaken so as to loosen the white deposit under the stopper. 



