ON MILK AND MILK-TESTING 35 



6. There should be means of ventilation for 

 temperature control. 



7. Bearings should be so placed that heat from 

 the steam will not affect them. 



8. Means should be provided for using a heavy- 

 oil where the bearings may become heated from 

 the steam. 



9. The bearings should be protected so that 

 acid cannot come in contact with them when bot- 

 tles break in the machine. 



How should the milk test bottles be constructed? 



1. The graduated portion of the neck should be 

 accurate. 



2. The bottles should hold about 50 c. c. and be 

 made of tough glass of even thickness throughout, 

 and strong enough to stand pressure and sudden 

 changes of temperature. 



3. The top of the body of the bottle should 

 slant toward its center at an angle not greater than 

 40 degrees, so that all the fat may rise in the neck. 



4. The bottom should be perfectly flat, so that 

 all points will be supported evenly while being 

 whirled in the machine. 



5. The diameter of the neck should be neither 

 too large nor too small, and should be the same as 

 other bottles in the set used. 



6. The top should be strong, well annealed, and 

 flaring, to readily admit the pipette and assist in 

 preventing loss when milk is introduced. 



How is the scale on the neck of the bottle divided? 



Each cubic centimeter of space is divided into 



five equal parts, each part equaling i per cent. 



