FARMERS' INSTITUTES. ]51 



GET A GOOD MACHINE. 



Do not buy a cheap machine. It does not pay. Get a good one while 

 you are about it, and buy of a reliable manufacturer. A good machine 

 should have a pan or jacket surrounding the head and bottles. This helps 

 retain the heat and also protects the operator in case of an accident from 

 a broken glass bottle full of hot acid. 



The pockets around the head should be suspended by a hinge joint so 

 that the bottles may assume a vertical position when at rest, and a nearly 

 horizontal position when under full speed. This is necessary in order 

 to secure perfect separation of the fat by centrifugal force, and also that 

 none of the contents of the bottles may be spilled when the machine is 

 suddenly stopped. 



Be sure that all the bottles selected are accurately calibrated. The 

 leading manufacturers of dairy and creamery supplies furnish bottles 

 guaranteed to be accurate. There are thousands of whole milk bottles 

 sent out that vary as much as 0.3 of one per cent in their calibrated neck 

 capacity from to 10. This space in the neck contains, in a perfect bot- 

 tle, exactly two cubic centimeters. 



The milk pipette should be so calibrated that it contains exactly 17.fi 

 cubic centimeters up to the mark above the bulb. The sulphuric acid 

 graduate should be marked to contain 17.5 cubic centimeters. 



TAKING A SAMPLE FOR TESTING. 



Be very careful to secure a fair sample for making a test. If you are 

 testing whole milk see that the sample taken rej)resents as nearly as pos- 

 sible the whole lot of milk taken from the cow to be tested, if an individ- 

 ual test. It is more satisfactory to test the sample while warm from the 

 cow, but just as good results may be obtained after waiting some time, 

 if the precaution is taken to thoroughly mix the milk so that the cream is 

 broken up and the whole mixture appears homogeneous. 



Samples that are fresh, or nearly so, may be well mixed by pouring two 

 or three times from one vessel to another. It is more diflScult to secure 

 a correct sample when the cream has coagulated or become dried, and too 

 much pouring or stirring when in this condition is liable to churn the 

 cream. 



As soon as possible after mixing the sample the pipette should be 

 inserted and the milk be drawn up into the tube above the mark by suck- 

 ing. Quickly remove the pipette from the mouth and firmly press the 

 index finger of the right hand over the upper end of the tube to exclude 

 the air. 



Now comes a particular job. Have the test bottle ready and hold the 

 pipette up in an upright position with the mark on a level with the eyes. 

 See that your finger end and also the end of the pipette is dry, in order 

 that you may prevent too much air getting into the tube when you 

 slightly raise your finger to let the upper surface of the milk lower to the 

 mark on the tube. Be sure that you have just the right amount of milk 

 in the pipette when the lower end of the pipette is inserted in the neck of 

 the test bottle. 



