208 CREAMERY BUTTER MAKING 



importance to use nothing but pure water for rinsing 

 cream vats and washing butter, else pasteurization will 

 prove a delusion. 



Purifying Water by Filtration. Most people are 

 familiar with the purifying action which water under- 

 goes in its passage through sand, gravel, charcoal, etc. 

 For purifying water used for washing butter, artificial 

 filter beds constructed of such material have given excel- 

 lent satisfaction. 



The filter can described in bulletin No. 71 from the 

 Iowa Experiment Station is 48 inches high, 18 inches in 

 diameter, and constructed of 22 gage galvanized iron. Be- 

 ginning at the bottom the filtering material was placed in 

 the can in the following order: i. 2 inches of small flint 

 stones ; 2. 22 inches of fine sand ; 3. 12 inches of fine coke ; 

 4. 9 inches of charcoal ; 5. 2 inches of fine stone or coarse 

 gravel. Two perforated plates are placed in the can, one 

 near the bottom upon which the filtering material rests, 

 the other on top of the fine sand. A third and concave 

 plate is placed near the top with a hole in the center, 

 which directs the water to the center of the filter bed. 



This can has a filtering capacity of 16 gallons per hour, 

 and it is claimed that the filter does not need to be cleaned 

 or renewed oftener than once in four months and possibly 

 not this often. The cost of the can is $11.11. 



Filtration offers one of the cheapest rrfethods of purify- 

 ing water and is the method generally employed by cities 

 that are dependent upon lakes for their water supply. 



Purification of Water by Heating. Water may be pas- 

 teurized in the same manner as cream. There is, how- 

 ever, one objection to this method of purifying water, 

 and that is the bad effect which it has on the pasteurizer. 

 In the course of time a distinct laver of the mineral im- 



