358 AGRICULTURAL BACTERIOLOGY 



disinfectant for such closed spaces as refrigerators and 

 other rooms in which the bleaching action of the sulphur 

 will be of no importance. It can not, as a rule, be used in 

 furnished rooms because of this property, which formalde- 

 hyde does not possess. 



Calcium hypochlorite. Bleaching pow'der or calcium 

 hypochlorite has long been used as a disinfectant and de- 

 odorant. Under certain conditions it is one of the most 

 effective that can be employed, as for example in the treat- 

 ment of water and sewage. Many cities draw their water 

 supplies from sources that may become contaminated with 

 typhoid bacilli. It has been found that the addition of 

 minute quantities of bleaching powder is sufficient to de- 

 stroy the typhoid organism. 



Calcium hypochlorite finds its widest use as a deodorant 

 for use in cellars, privies, and similar places. For these 

 purposes the dry powder is usually employed. 



It can be used for the treatment of cisterns in which a 

 large amount of organic matter has been carried by the 

 wash from the roofs. During the warm weather the de- 

 composition of the organic matter may be so marked as to 

 impart a disagreeable odor to the water, which can be over- 

 come by the addition of a solution of bleaching powder. 

 The amount to be added will depend on the quantity of or- 

 ganic matter in the water. It should be added in small 

 quantities, as an excess will impart the characteristic odor 

 of the hypochlorite to the water. 



Ferrous sulphate and copper sulphate. These sub- 

 stances, commonly known as green and blue vitriol, have 

 been widely used as disinfectants in the past. 



It is now known that they are almost worthless and 

 should be discarded in favor of some one of the efficient 

 disinfectants. 



Disinfection. The choice of a disinfectant for any par- 



