230 



ities advise, after whirling the bottles Ave minutes, to add or 

 to fill the bottles with hot water up to the neck ; whirl them 

 one minute ; then fill with hot water up to the point 7 and 

 whirl again for one minute. After the last whirling take out 

 the bottles, stand them in hot water, read and record the per- 

 centages of fat. The per cent, of fat is indicated by the 

 length of the column of liquid fat in the graduated neck of 

 the milk tube. In measuring the length of the fat column 

 the reading should be taken from the lower end to the 

 extreme upper limit of the fat. 



The color of the fat will indicate to some extent the strength 

 of the acid used : if the fat is quite dark the acid is too strong ; 

 if white, undissolved material collects at the bottom of the 

 fat ; or the fat is very light in color, the acid is too weak ; if 

 the fat has a golden yellow color the acid has the proper 

 strength. 



The following precautions should be used in making the 

 Babcock test: 



1. Secure a fair or average sample of the milk. The Scovell 

 sample tube or the "milk thief" may be used in procuring 

 samples from a large dairy can. 



2. Secure acid of proper strength; acid having 1.82 specific 

 gravity is usually the best. If the milk is very rich 20 to 21 

 c. c. of the acid may be used. 



3. Be careful to pour the acid into the bottle so that it will 

 follow the inside surface of the bottle to the bottom. This 

 can be accomplished by slightly inclining the neck of the test 

 bottle. 



4. Carefully, slowly and thoroughly mix the acid and milk 

 in the bottle. 



5. In adding hot water to the bottles to bring the column 

 of fat up into the graduated neck, use soft, rain, or distilled 

 water ; never use hard water. 



6. Be careful in measuring the fat ; it must be kept hot by 

 standing the bottle in hot water, in order to measure it cor- 

 rectly. 



7. Keep the acid tightly corked with a rubber or glass stop- 

 per, because it will quickly absorb moisture from the air and 



