142 MANUAL OF BACTERIOLOGY. 



and Kellerman,* and various investigators tested the value 

 of their recommendation. 



Clark and Gagef came to the conclusion from their investi- 

 gation that the treatment of water with copper sulphate or the 

 storing of water in copper vessels has little practical value. 

 Others also have come to practically the same conclusion. 

 While the addition of copper sulphate is of use in preventing 

 the growth of the algae, which sometimes grows so abundant, 

 as to choke up water pipes, is of benefit in this direction, the 

 weight of evidence appears to be against its efficacy for purifying 

 water for drinking purposes. The use of ozone for the puri- 

 fication of water has met with considerable favor. J 



The filtration of water on a small scale, as is ordinarily done 

 for domestic purposes, is generally entirely useless. The so- 

 called Pasteur filter of unglazed porcelain is effective if it is 

 properly constructed and if the filter-tubes are sterilized by 

 heat every few days conditions which are seldom complied 

 with. Distillation of water and boiling are the most practical 

 methods for sterilizing drinking-water. 



Collection of Samples. For bacteriological examination 

 samples from the water-supply of a city may be drawn from 

 the faucet, but the water should first be allowed to run for half 

 an hour or longer. From other sources the supply should 

 be collected in sterilized tubes or bottles, taking care to avoid 

 contamination. Sternberg bulbs (see Fig. 38) will be found 

 useful for small samples. These samples should be examined 

 as quickly as possible, for the water bacteria increase rapidly 

 in number after the samples have been collected. When trans- 

 portation to some distance is unavoidable the samples should 

 be packed in ice, but even this precaution does not preserve 

 the original bacteriological condition of the water at the time 



*U. S .Dep. Agriculture. Bu. Plant Ind. Bulletin 64, 1904. 

 ~\Journ. Inf. Diseases. Sup. No. 2, Feb., 1906, pp. 175-204. 

 ^Consult Rosenau. Disinfection and Disinfectants. 1902. 



