l8o PHARMACEUTICAL BACTERIOLOGY. 



proven unsatisfactory for various reasons. The use of high attenuations 

 (1-5,000,000 to 1-50,000) of copper sulphate has been highly recommended, 

 especially by the U. S. Dept. of Agriculture, and has in many instances 

 giveji excellent results, especially in the destruction of low forms of algse 

 and protozoa. As a means of destroying bacterial life the method is, 

 however, not a success. Dr. Kraemer and others recommend the use of 

 copper foil or plates immersed in the water as a means of destroying patho- 

 genic and other bacteria, but this method does not appear to have met 

 with any general approval. Kraemer sums up the copper foil treatment 

 of water as follows: 



1. The intestinal bacteria, like colon and typhoid, are completely de- 

 stroyed by placing clean copper foU in the water containing them. 



2. The effects of colloidal- copper and copper sulphate in the purifica- 

 tion of drinking water are in a quantitative sense much like those of filtra- 

 tion, only the organisms are completely destroyed. 



3. Pending the introduction of the copper treatment of water on a large 

 scale the householder may avail himself of a method for the purifications 

 of drinking water by the use of strips of copper foil about 31/2 inches square 

 to each quart of water, this being allowed to stand over night, or from six 

 to eight hours, at the ordinary temperature, and then the water drawn off 

 or the copper foil removed. 



The alum method of purifying water has met with considerable success, 

 but more recently the alum-sodium hypochlorite combination has proven 

 more satisfactory. The alum coagulates and precipitates the organic im- 

 purities and the sodium hypochlorite, through its electric dissociation, acts 

 as a germ destroyer. The coagulated and precipitated organic material 

 holding most of the bacteria is then removed by filtration. The amount of 

 chemicals used depends somewhat upon the degree of contamination. With 

 highly contaminated waters it is customary to use 3.3 per cent, of alum as 

 the coagulant, subsequently introducting 1.2 per cent, of the hypochlorite. 

 The water is then filtered, whereupon it is ready for use. 



Small quantities of drinking water may be purified as follows: Dissolve 

 a level teaspoonful of powdered chloride of lime in a teacup of water. This 

 solution is diluted with three cupfuls of water, and a teaspoonful of the 

 whole quantity is added to each two-gallon pail of drinking water. This will 

 give 0.4 or 0.5 part of free chlorine to a million parts of water and will, in 

 ten minutes, destroy all typhoid and colon bacilli or other dysentery-produc- 

 ing organisms in the water. Moreover, all traces of chlorine will disappear 

 rapidly. 



There are in use a number of methods for dissociating sodium hypochlor- 

 ite by electricity. Some of them are patented and modifications thereof are 

 in use by city water purification works, giving excellent results. Dr. C. P. 



