In 1890 Dr. S. M. Babcock of the Wisconsin Experiment Station invented a wonderful little machine that quickly and cheaply measures the fat in milk. Few machines are more useful. So desirous was Dr. Babcock of helping the farmers that he would not add to the cost of his machine by taking out a patent on his invention. His only reward has been the fame won by the invention of the machine, which bears his name. This most useful tester is now made in various sizes so that every handler of milk may buy one suited to his needs and do his own testing at very little cost.
The operation of the machine is very simple. Suppose that the members of the class studying this book have been asked to take a Babcock machine and test the milk of a small herd of cows. They can readily do so by following these directions:
While the milk is still warm from the first cow to be tested, mix it thoroughly by pouring it at least four times from one vessel to another. A few ounces of this mixed milk is then taken for a sample, and carefully marked with the name of the cow. A number is also put on the sample, and both the cow's name and the number entered in a notebook. A small glass instrument, called a pipette, comes with each machine. Put one end of the pipette into the milk sample and the other end into the mouth. Suck milk into the pipette until the milk comes up to the mark on the side of the pipette. As soon as the mark is reached, withdraw the pipette from the mouth and quickly press the forefinger on the mouth end. The pressure of the finger will keep the milk from running out. Then put the lower end of the pipette into one of the small long-necked bottles of the machine, and, lifting the finger, allow the milk to flow gently into the bottle. Expel all the milk by blowing through the pipette.
The next step is to add a strong, biting acid known as sulphuric acid to the test-bottle into which you have just put the milk. A glass marked to show just how much acid to use also comes with the machine. Fill this glass measure to the mark. Then pour the acid carefully into the test-bottle. Be sure not to drop any of the acid on your hands or your clothes. As the acid is heavier than the milk, it will sink to the bottom of the bottle. With a gentle whirling motion, shake the bottle until the two fluids are thoroughly mixed. The mixture will turn a dark brown and become very warm.