READING 311 



required force is being developed. Continue even, strong turn- 

 ing for four minutes, when the machine should be permitted to 

 stop of its own accord, or gently retarded by hand. 



Adding Water. — Clean, soft water, just below the boiling 

 point in temperature, is to be added, at this point in the process, 

 to each bottle in amount sufficient only to bring the contents up 

 to the bottom of the neck. This enables any curdy matter 

 which may be floating on the heavy acid mixture to settle and 

 not clog the neck. 



Second Whirling — Again the machine is to be strongly 

 turned as before, for three minutes, and then gently stopped. 



Finish Adding Water. — At this point more hot water should 

 be added, sufficient to bring the top of the fat column to within 

 about one inch of the top of the bottle, care being taken not to 

 run it over. 



Third Whirling — Again the machine should be run two 

 minutes strongly at full speed. This last whirling is particu- 

 larly necessary in removing or squeezing the water out of the fat 

 column in the neck of the bottle. 



Reading. — Test bottles are graduated to agree with the 

 expansion of the fat when at a temperature of 130 to 140 degrees 

 (Fig. 106). In hand machines there is a constant danger that 

 the fat will be read at so low a temperature that it will not in- 

 dicate as high a fat percentage as necessary to secure correct 

 results. Furthermore, the fat column should be read from the 

 bottom of the bottom meniscus to the extreme top as indicated 

 in the figure. Although there is a depression, called the menis- 

 cus, on the top of the fat column it has been shown that the 

 quantity of fat which would be required to fill this depression 

 is equalled by the amount of fat which regularly remains in the 

 bulb of a good test bottle, and never enters into the fat column. 

 The amount of fat in the column is determined by spreading the 

 dividers from the bottom to the extreme top of the fat column, 

 then by placing the lower point at zero and noting the place 

 indicated by the upper point. The distances between the fine 



