Il62 



Rural School Leaflet 



Place the bottles in the machine so that each one will have another 

 directly opposite, in order to keep the machine in balance. Whirl the 



bottles five minutes at the proper speed for 

 the machine in use (Fig. 6). Then stop it 

 and, with the pipette or other convenient 

 means, add hot water to each bottle until the 

 „ »flni contents come up to the bottom of the neck. 

 Whirl two minutes. Add enough hot water 

 to bring the top of the fat nearly to the top 

 of the graduations on the neck of the bottles. 

 Whirl one minute. The fat should then form 

 a clear column in the neck of the bottle. 



Reading the percentage. — Keep the fat 

 in a fluid con- 



Fig. 4. — Mixing milk and acid. 

 A rotary motion, with the bottle 

 not pointed toward the face 



warm so that it will be 



dition. Hold the bottle by the upper end 



of the neck, letting it hang in a perpen- 

 dicular position, on a level with the eye. 



Read the marks, or graduations, at the 



extreme top and bottom of the fat column. 



The difference between these is the percent- 

 age of fat in the milk. Some test-bottles 



are made to read as high as 10 per cent, 



while others read only to 8 per cent. Each 



percentage has its number marked on the 



glass, and on the 10-per-cent bottles there 



are five small spaces each representing 



.2 per cent between these principal marks. Thus, if the top of the 



fat column is even with the third short mark above 

 the 7 mark, the top reading would be 7.6; and if 

 the bottom is halfway between the first and second 

 short marks above the 3 mark, the bottom read- 

 ing would be 3.3; the difference is 4.3, which is 

 the percentage of fat or the number of pounds of 

 fat in 100 pounds of the milk tested. On the 

 8-per-cent bottles there are ten small spaces be- 

 tween each percentage mark, and each space 

 represents one tenth of one per cent. 



Fig. 5. — Putting the milk in- 

 to the test-bottle. The pipette 

 is held at an angle with the 

 test-bottle, with its point against 

 the inside of the neck 



Fig. 6.— Whirling the Notes 



One cc. means 1 cubic centimeter, or about 20 drops. 



If the fat column is clouded with white specks, probably the acid was not 



strong enough, or not enough was used, or the heat was not high enough. 



