68 A Ne^' Dairy Industry. 



In sterilizing by steam it is necessary that all air 

 be driven out of the apparatus, because a mixture of 

 air and steam gives very unsatisfactory results ; the 

 apparatus should, therefore, be fitted with an escape 

 pipe, through which all air may be driven out and a 

 sufficient amount of steam may also continuously es- 

 cape during the entire duration of sterilization, so as 

 to maintain a circulating movement of the steam in- 

 side of the apparatus ; this is essential to equalize the 

 temperature in all parts of the apparatus, for, with- 

 out such movement of the steam, either the bottles 

 nearest to the entrance of the steam will be over- 

 heated or those more remote not attain the desired 

 degrees of heat. We have seen that a thermometer 

 is attached to the hood of the apparatus to indicate 

 the heat of the steam as it fills the inside, enabling 

 the operator to regulate the flow in such a manner as 

 to secure a steady rising of the temperature not ex- 

 ceeding f> F. in every minute. But the tempera- 

 ture of the steam in the apparatus is no indication of 

 the temperature of the milk in the bottles to be steri- 

 lized, and to know which is of the greatest import- 

 ance. For this reason it is necessary to fix a second 

 thermometer in the hood of the apparatus, exposing 

 the scale of degrees outside, whilst the quicksilver 

 bulb reaches down and dips into the milk in one of 

 the bottles inside. This bottle, or rather a bottle 

 with the neck trimmed off, so as to offer a wider 

 mouthed opening for the thermometer bulb to dip 

 into, is so fixed on a bracket that the thermometer de- 



