Cream Testing. 77 



The figures in the table show plainly the variations in 

 the specific gravity of cream of different richness and 

 the error of making tests of cream by measuring it with 

 a 17.6 cc. pipette, especially if the pipette is not rinsed 

 and the washings added to the test bottle; if the cream 

 to be sampled is fresh separator cream testing over 30 

 per cent, less than 17.0 grams of cream will be delivered 

 into the test bottle, and the results of the reading will 

 be at least one-eighteenth too low, or about 1.4 per cent, 

 on a 25 per cent, cream. If the cream is sour, the error 

 will of course be still greater. 



It should be remembered that the specific gravities of 

 the cream given in the table refer to fresh separator 

 cream only. Considerable air is incorporated during the 

 separation, and cream of this kind is therefore lighter 

 than gravity cream of corresponding fat contents. 



88. Avoiding errors of measuring cream. The preced- 

 ing table shows that a 17.6 cc. pipette in case of cream 

 containing less than 25 per cent, of fat and fresh from 

 the separator, will deliver only about 17.2 grams of 

 cream; it is therefore evident that the pipette to deliver 

 cream for the Babcock test must be made larger than the 

 17.6 cc. pipette used in testing milk. Quite satisfactory 

 results may be obtained in testing such cream by using 

 an 18 cc. measuring pipette; to avoid the expense and 

 trouble of using two different pipettes, one for milk and 

 one for cream, a pipette with two marks on the stem, at 

 17.6 cc. and 18 cc., has been placed on the market, the 

 former mark being used when milk is tested, and the 

 latter for cream. 1 



i Professor Spillman, in Bull. 32 of Washington experiment station, 

 recommends the use of a 17.6 cc. pipette for testing cream, the results ob- 

 tained being corrected by a certain per cent., as shown in a table given in 

 the bulletin. The table is based on the figures given on p. 76 of this book, 

 and is therefore only applicable to fresh separator cream. 



