TRUE AVERAGE TEST OF CREAM 321 



the fat into the neck, and also to insure separating the water 

 from the column of fat. 



The Use of a " Reader." — It will he noted, as shown in 

 figure 110, that the depression or concave portion on the top of 

 the fat column, in the case of cream, amounts to considerable. 

 The quantity of fat which would be necessary to fill up this 

 concave area, or meniscus, is altogether greater than the amount 

 of fat which remains in the bulb of the bottle; consequently 

 allowance must be made for the depression. Or better still, 

 some substance like amyl alcohol, colored red with some dye, or a 

 lightweight machine oil, as glymol, may be added to flatten the 

 surface. It has been the experience of the writer that the oil 

 obtainable varies considerably in weight and is less reliable than 

 the alcohol. The substance usually sold by creamery supply 

 companies is mostly amyl alcohol colored with a dye. 



Reading the Sample. — The reading is done the same as in 

 the case of the milk. It is a little more important, however, that 

 a temperature of at least 130 to 140 degrees be maintained, 

 since the fat column is so long. The reading should be made 

 from the extreme bottom to the flat surface shown between the 

 red reader and the fat, or in the case no " reader " is used the 

 upper part of the dividers should be made to divide the distance 

 occupied by the meniscus about equally (Fig. 111). 



It is impossible to test cream to the same point of accuracy 

 as that reached in the case of milk. This is due to the wide neck 

 in the bottle which it is necessary to use. Therefore it is found 

 that a variation of one-half per cent in duplicate samples of 

 sour cream is not at all uncommon and would almost be expected. 



Calculating the Fat in Cream. — A ten-gallon can will hold 

 about 84 pounds of ordinary cream. If this is shown to test 34.5 

 per cent, the quantity of fat in the can is found by multiplying 

 84 by 0.345 ; thus 84 times 0.345 equals 28.98 pounds of fat. An 

 eight-gallon can will hold about 67 pounds of ordinary cream. 

 If the test shows this to contain say 26.5 per cent fat there will 

 be contained in it a quantity of fat found by multiplying 64 by 

 0.265, or 17.80 pounds of fat. 



True Average Test of Cream. — The chief reason why it is 

 21 



