EFFECT OF COPPER UPON WATER BAC^'l'ERlA. 



09 



To dotcrmino whothor the peculiar variation in the germicidal power 

 of .solution!? or iiietaLs is due to the u.se of ordinary hiboratorv ohissware 

 made of a rather soluble glass instead of carefully selected highly 

 insoluble glass, a parallel series in good and poor glass was carried on. 

 The following tables show the slight ditference in results: 



Table XXX. — Effect of glcma upon toxiciUj of metals to Bacillu.'t coli.^ 



1 Experiment conducted in ordinary gla.'ss te.«t tubes each containing 10 c. c. of water triple distilled 

 from glass, to portions of which were" added sterile blocks of the proper metals, each having approxi- 

 mately 2 sq. cm. surface area. All tubes inoeulated- with a 2 mm. loop of culture of I}arillu.t colt 

 received from Prof. Theobald Smith. The temperature during this experiment varied from 18° to 

 22° C. 



Table XXXI. — Effect of glass upon toxicity of metals to Bacillus coliJ 



' Experiment conducted in Weber resistance glass test tubes each containing 10 c. c. of water triple 

 di.stilled from glass, to portions of which were added sterile blocks of the pn)i)cr metals, each having 

 approximately 2 sq. cm. surface area. All tubes inoeulated with a 2 mm. loop of culture of HuclUus 

 coli received from Prof. Theobald Smith. The temperature during this experiment varied from 18° 

 to 22° C. 



COPPER SULFATE AND FILTRATION. 



The use of copper sulfate in connection with liltration has been 

 mentioned in previous bulletins. Further experiments in this tield 

 show that in mechanical filtration with alum it is necessary" to limit 

 the use of copper sulfate to treatment some hours before coagula- 

 tion. When solutions of aluminum sulfate and copper sulfate are 

 mixed and alkali or hard water is added in quantities sufficient to 

 cause precipitation the copper is coagulated at once, while the alu- 

 minum is deposited on the copper and incloses it, with the result that 

 the copper-alum coagulum is no more toxic than is the pure alum coag- 

 ulum. When copper and iron .salts are precipitated together the 

 reverse of this seems to take place and the precipitate retains its toxic 

 properties.* 



a See.also H. W. Clark, Sulphate of Alumina as a Germicide. Thirty-sixth Annual 

 Report of State Board of Health of Massachusetts, 1904, p. 288. 



100— vu 



