372 



Testing Milk and Cream. 



[SEPT., 



than they had previously obtained from the same measure under 

 the whole milk system. 



Emphasis is laid in the Report on the necessity for obtaining 

 a sample of uniform composition, and also of weighing rather 

 than measuring the sample used for the test bottle, but the 

 most interesting feature of the work is an examination of the 

 effect of the curved surface of the fat, or meniscus, as it is 

 termed, in bottles of different diameters. A series of thirteen 

 bottles were selected, ranging in diameter of neck from '23 

 of an inch to nearly "59 of an inch. The bottles were filled 

 with water to some point in the lower part of the neck, and 

 then 1 grain (representing 5*55 per cent.) of pure butter-fat 

 was weighed into the neck. The bottles were whirled in a hand 

 tester and read at 120 degrees F. Readings from the extreme 

 top to the bottom of the fat column were carefully made, 

 and the depth of meniscus measured. The result showed that 

 the 10 per cent, milk bottles, having a diameter of neck of about 

 a quarter of an inch, gave a reading of 570 and 5*80 respectively, 

 while the 50 per cent. 6-in. cream bottles, having a diameter 

 of over half an inch, gave a reading of from 7 to 7*40 per cent., 

 the depth of the meniscus in the latter case being ten times 

 as great as in the former. It will be seen that the 10 per cent, 

 milk bottles read more than the true amount, whereas in 

 general practice the reading of these bottles is supposed to 

 indicate the amount exactly. In ordinary milk testing it is 

 estimated that about two-tenths of 1 per cent, adheres to the 

 inside of the bottle below the neck, and that the total length 

 of the fat column will give a correct reading. In these experi- 

 ments, however, the fat was weighed into the neck of the 

 bottle, and was, therefore, known to be all in the neck, so that 

 the effect of measuring the whole of the curved surface seems 

 as apparent in the case of the 10 per cent, bottles as with 

 the others. The excess over the true amount and the depth 

 of the meniscus was found to increase regularly as the necks 

 of the bottles increased in diameter, and it was evident that 

 the true reading would fall somewhere between the reading of the 

 top and the reading at the bottom of the curved surface of the 

 fat. A careful inspection showed that if from the total length 

 of the fat column there were deducted four-fifths of the depth 



