8 



cloths ; then allow the water in the vessel to boil 30 to GO 

 minutes. This will usually keep the milk sweet as long as 

 the bottles are kept closed. During the hot part of last sum- 

 mer I kept milk that had been so sterilized for 6 weeks, and 

 the bottles stood in a window where the sun could shine on 

 them part of the day. As a rule, on account of reasons pre- 

 viously stated, it is not good to sterilize milk at such a high 

 temperature. But drinking water should always be sterili- 

 zed by this method. 



If milk is acid in reaction ( slightly sour ) before steriliza- 

 tion it will coagulate after sterilization, although it may be 

 free of germs. Sometimes the milk is acid when it comes 

 from the udder and this is said to be due to improper feeding 

 of the cow. In order to determine if the milk is appreciably 

 acid before sterilization, put a small strip of blue litmus pa- 

 per into the milk ; if it turns red the milk is acid, but if this 

 produces no change in the blue paper the milk is neutral or 

 alkaline. If the milk is slightly acid it may be made neutral 

 or slightly alkaline by the addition of a sufficient quantity of 

 a saturated solution of bicarbonate of potassium, or com- 

 mon baking soda, to make the red litmus paper turn blue. 

 This may be done without injuring the milk, if practiced 

 with care. . » 



In sterilizing water, always heat it to 212 degrees, F., for 

 30 to 60 minutes. After the water in the sterilizing vessel 

 has become partially cooled, the bottles may be placed on 

 ice, put in cold water or transferred to a bucket that may be 

 hung in the well. 



The only practical method of using the thermometer, when 

 sterilizing milk, is the one suggested by the Bureau of Ani- 

 mal Industry. It is adjusted in the lid so that the bulb is 

 immersed in the water of the vessel. The vessel is filled with 

 water as high as the level of the milk, in the bottles. , 

 When the water reaches the desired temperature ( 160 to 167 

 degrees, F.,) the vessel is removed from the fire,, covered 

 with cloths and allowed to stand 30 to 40 minutes. 



