17 



Notes. 



1. Always make sure that the pipettes and test bottles are clean 

 before using. 



2. Be very careful to measure th^ exact amount of milk for a test. 

 A 17.6 c.c. pipette will delivpr about 17.5 c.c. of milk. This measure- 

 ment of milk of average quality will weigh about 18 grams. 



3. A partially churned sample of milk may be prepared for samp- 

 ling by heating it to about 110 degrees F.. and pouring it from one 

 v^essel to another, to mix it thoroughly. When it is thus prepared, 

 take a sample as quickly as possible, and cool to about 60 degrees F. 

 before adding the acid. 



4. In sampling frozen milk it is necessary that both the liquid 

 and the frozen part be warmed and mixed thoroughly. The unfrozen 

 part is richer in fat and solids than the frozen. 



5. A sample of milk that has soured and thickened may be pre- 

 pared for sampling by adding a small amount of some alkali to neutral- 

 ize the lactic acid, and cause the curd to redissoive. A small amount 

 of powdered concentrated lye is very suitable. Add just <i small amount 

 of lye at a time, and pour the milk from one vessel to another, to mix 

 the lye with the milk, which causes the casein to become dissolved. 



6. The amount of acid used must be varied to suit its strength. 

 The right amount is being used when the fat presents a bright golden 

 appearance. Acid that is much too strong or too weak should be dis- 

 carded, as satisfactory results cannot be obtained from its use. Acid 

 a little weak is to be preferred to very strong acid. Carboys or bottles 

 containing acid should be kept well corked, to prevent the contents 

 from becoming weakened by absorbing moisture from the atmosphere. 



7. Avoid pouring the acid directly on the milk. The test bottle 

 should be held at an angle so as to cause the acid to follow the side 

 of the bottle and go directly underneath the milk. After the addition 

 of the acid to the test bottle the milk and acid should De in two dis- 

 tinct layers without any charred matter between them. A thorough 

 mixing by means of a gentle rotary motion should be given at once. 



8. If using a hand tester in a room at a low temperature, it may 

 be necessary to keep sufficient hot water in the machines to maintain 

 a temperature of from 120 to 140 degrees F in the test bottles. 



9. The water added to the test bottles should be soft or distilled. 

 If hard water is used, add a little sulphuric acid (half an acid measure, 

 or a little more to a gallon of water) to soften it; this will prevent 

 foam above the fat. 



10. If there are several readings to take, ahvays set the samples 

 in hot water (120 to 140 degrees F.) extending to the top of the fat be- 

 fore reading. 



11. It is well to use a pair of dividers or compas.>,es for measur- 

 ing the column of fat. The points of the dividers should be placed at 

 the upper and lower limits of the fat column ; then if one point be plac- 

 ed at the zero mark of the scale, the division at which tne other point 

 touches will show the percentage of fat in the sample tested. 



3— BULL. 143 



