MILK 235 



Preserving Samples. If it is necessary to keep the milk samples 

 several hours or days before testing, a preservative should be added 

 to prevent curdling, and the bottles kept tightly stoppered. The 

 preservative most commonly used 15 corrosive sublimate (a poison). 

 This is sold in the form of tablets, in boxes containing 100 or 1,000. 

 Each tablet also contains some pink coloring matter, so that every- 

 one may know that the milk, so colored, contains poison, is unfit to 

 drink, and must not be fed to stock. One small preservative tablet 

 should be dropped into each bottle of milk and shaken until dis- 

 solved. The box containing the tablets should be kept out of the 

 reach of children. Borax and bichromate of potash are other pre- 

 servatives which may be used instead of the tablets. 



Filling the Pipette. The milk test bottle and pipette are cleaned 

 with hot water and washing powder or soap, if necessary, and thor- 

 oughly rinsed with clean water before using. For the Bafocock test 

 17.6 cc. of milk (18 grams) is measured with the pipette and trans- 

 ferred to the test bottle without loss. 



It should be remembered that cream is always rising in milk, 

 whether it can be seen or not. Before taking any milk out of the 

 small sample bottle with the pipette the sample bottle should be well 

 shaken, so as to mix the cream all through the milk. If lumps of 

 butter fat appear on the surface of the milk, warm the bottle and 

 contents to about 100 degrees and shake again. Immediately put 

 the narrow tip of the pipette into the milk (while it is still in motion) 

 and with the mouth, suck the air out until the milk rises in the 

 pipette, above the mark on the neck. Quickly place the forefinger 

 over the upper end of the pipette, before the milk runs down below 

 the mark. If the finger is dry it is easy, by changing the pressure 

 on the end of the tube, to let the milk run down slowly and to stop 

 it exactly at the mark. 



Filling the Test Bottle. The tip of the pipette is next placed in 

 the top of a test bottle, held in an inclined position and the milk is 

 allowed to run down one side of the neck of the 'bottle, without filling 

 the neck completely, or preventing the escape of air. In this way 

 exactly 18 grams (17.6 cc.) of milk is transferred to the test bottle 

 without loss. It is well for a beginner to practice this work with 

 the pipette filled with water until the flow can be readily controlled 

 with the forefinger. If at any time a portion of the milk containing 

 preservative is drawn into the mouth, reject it, and rinse the mouth 

 with clean water. After the samples of milk have been placed in 

 the test bottles, they can be set aside for a day or a week, if neces- 

 sary, and the testing can be finished at any time. 



Adding the Ac id. -Sulphuric acid of specific gravity 1.82 is 

 next added to the milk in the test bottle. It can be obtained at any 

 drug store or of dealers in dairy supplies. The acid is first poured 

 into the little acid cylinder which holds just 17.5 cc. when filled to 

 the mark. The cylinder is then emptied into the test bottle, which 

 is held in an inclined position to permit escape of air, and avoid 

 spilling the acid. Since this acid destroys wood and metals, the bot- 

 tle of acid and the little measuring cylinder should be kept standing 



