168 MARKET DAIRYING 



this needs to be done is, of course, dependent upon the 

 amount and character of the impurity in the water. Boilers 

 are kept clean in three different ways, (i) by blowing 

 off at low pressure, (2) by cleaning through manhole, 

 and (3) by using boiler compounds. 



(i). By blowing the boiler off at low pressure most 

 of the mud will be blown out. But care must be taken 

 that the pressure is not above ten pounds and that there is 

 no more fire in the fire box, otherwise the mud, instead 

 of flowing out with the water, will bake on and form 

 scale. 



(2). A good way of removing mud is to allow the 

 boiler to cool off and then run a rubber hose through the 

 manhole. By working the hose and forcing water 

 through it the sediment can be removed. 



(3) Boiler compounds are used to -keep boilers free 

 from scale. The kind of compound to be used is deter- 

 mined by the character of the impurities of the water. 

 Most dairies use well water for the boiler and the chief 

 impurity in this is lime. The best compound for water 

 of this kind is soda. Well water contains the lime in 

 widely different proportions. In order, therefore, to as- 

 certain the proportion of soda to feed water the following 

 method is recommended by Hawkins: 



"i. Add one sixteenth part of an ounce of soda to a 

 gallon of the feed water and boil it. 2. When the sedi- 

 ment thrown down by the boiling has settled to the bottom 

 of the kettle, pour the clear water off and add one-half 

 drachm of soda to this. Now, if the water remains clear, 

 the soda which was put in has removed the lime. But 

 if it becomes muddy, the second addition of soda is neces- 

 sary." In this way the amount of soda to be added to 

 the feed water can be calculated with sufificient accuracy. 



