TESTING MILK AND OREAM. 35 



sidered most accurate. The use of the 50 per cent 

 six inch cream test bottle should be avoided. Buy 

 only first class bottles, as these are most accurate, 

 but all bottles should be tested for correctness of 

 calibration. Even bottles which are guaranteed cor- 

 rectly calibrated cannot alvs^ays be depended upon 

 as accurate. 



Note: For further information regarding the 

 reading of cream tests, comparison of cream test 

 bottles, and mathematical calculations involved in 

 testing cream, consult Book II, Chapter V 



42. Using colored alcohol for reading cream tests. 

 Butter fat has a specific gravity of about .90. Al- 

 cohol has a specific gravity of about .816, and amyl 

 alcohol has a specific gravity of .8294. It is advis- 

 able to be sure to get the properly colored amyl 

 alcohol for this use. 



The adding of the colored alcohol must be done 

 carefully, so that the fat and alcohol do not mix, 

 and so that the alcohol does not run down between 

 the fat column and the neck of the bottle. 



Some of the colored liquids on the market seem 

 to mix very readily with the butter fat and those 

 which do this are likely to cause considerable 

 trouble. An experienced cream tester can read the 

 tests more quickly and accurately without the ad- 

 dition of the colored alcohol. With some of the 

 colored liquids now used, the upper line of the fat 

 column had an upward curve, which made the exact 

 reading more difficult than when no colored liquid 

 was used. Therefore, I wish to warn the inexperi- 

 enced operator against the use of a colored liquid 

 unless he is sure that it is reliable. 



