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Cream test-bottles are graduated to read 30, 40, or oO per cent, 

 fat, and differ from whole milk bottles only in the diameter of the 

 neck. The intermediate size is usually the most satisfactory for 

 factory work. The scale on the neck of the ordinary luiik or cream 

 test bottle is graduated to read directly the per cent, of fat, only when 

 18 grams are used in the test, i.e., the fat extending- over one of the 

 larger divisions of the scale weighs one per cent., or the one-hundredth 

 part of 18 grams. This fact will explain the various i iles for deter- 

 mining the per cent, of fat when 18 grams cannot be u ;a in a test — 

 as in the case of cream and cheese, in which the per jent. of fat is 

 high. 



Rule. To find the per cent, of fat when less than 18 grams has 

 been used ; multiply the reading obtained by 18 and diviae by the num- 

 ber of grams used. 



This weight may be most accurately obtained by means of a deli- 

 cate balance, but in the hands of the average dairyman it is a ques- 

 tion if the use of a balance would result in greater accuracy than a 

 pipette for sampling cream in a normal condition. The specific grav- 

 ity of average cream (25 to 30 per cent.) being nearly one, the weight 

 delivered by an 18 cc. pipette would be approximately the required 

 amount, viz., 18 grams. 



During the process of cream ripening, however, more or less gas 

 is usually formed which tends to reduce the specific giavity and thus 

 lessen the weight of a given volume of the cream. It will thus be seen 

 that sour cream sampled with a pipette would tend to give readings 

 slightly lower than* sweet cream. The difference in the test would 

 scarcely be perceptible at a low per cent, of acid, but would be more 

 marked at a high, sharp, acidy condition. 



The use of a pipette for sampling in creamery work piaces a slight 

 premium on sweet cream, thus affording a pertinent means of discrim- 

 inating against overripe and otherwise objectionable grades of cream. 



A sample containing an unusual amount of air or gas may be more 

 accurately sampled if warmed to a temperature of about 110 degrees 

 F. and after the necessary mixing, cooled to about 60 degrees F. 



Notes. 



1. A pipette graduated to read both 17.6 cc. and 18 -cc. is a 

 convenience, the former measurement beinc" required for whole milk, 

 skim milk, butter milk, and whey, and the latter for cream. 



2. When sampling viscous cream the pipette should be rinsed with 

 about one-third measure of warm water, which should be added to the 

 test bottle. 



3. The addition of a small amount of caustic soda ur concentrated 

 lye to viscous or lumpy samples renders sampling moie speedy and 

 accurate. 



4. Composite samples of cream may be cared for and treated in 

 the same manner as outlined for milk under the beading, "Composite 

 Samples." Page J 8. 



