MODERN METHODS OF TESTING MILK 



Requirements for bottles. In the selection of 

 cream-testing bottles, certain points should be kept in 

 mind, such as (i) accuracy of reading, (2) ease of 

 reading, (3) convenience of handling and (4) dura- 

 bility. 



1 i ) Accuracy of reading. The accuracy with which 

 the percentage of fat can be read depends upon (a) 

 the diameter of the neck, (b) the length of the neck 



and (c) the amount of cream used 

 (9 or 1 8 grams). The larger the dia- 

 meter of the neck, other conditions 

 being uniform, the greater is the per- 

 centage represented by each division 

 of the scale, and, consequently the less 

 the accuracy of reading. The longer 

 the neck, other conditions being the 

 same, the smaller is the percentage of 

 fat represented by each division and, 

 therefore, the greater the correctness 

 of the reading. The length and dia- 

 meter of neck being the same, a bottle 

 with neck graduated on the basis of 

 using a 9-gram sample of cream per- 

 mits more accurate reading than when 

 based on 18 grams. For accurate 

 work, no bottle should be used in 

 cream-testing in which the finest divi- 

 sion of the graduated scale represents 

 more than 0.5 per cent. 



(2) Ease of reading. This depends mainly upon 

 the diameter of the neck; the greater the diameter, 

 other conditions being the same, the more difficult is 



FIG. 290 



STRAIGHT-NECKED 



CREAM-BOTTLE 



