16 METHOD OB^ DESTROYING ALG^ IN WATER SUPPLIES. 



seems that copper sulphate is the substance best adapted to the work 

 in question. This salt has a very high toxicity for algje, and experi- 

 ments with a number of the forms usually found in reservoirs, and 

 the source of much trouble, have shown that inconceivably small 

 amounts of copper are poisonous in a high degree. These experiments 

 demonstrated, however, that all algte and protozoa are not equally sen- 

 sitive. Among the latter Paranisecluiii is killed in three hours by a 1 

 to 1,000,000 solution, while Anueha, lJlJfiu<j(a^ and SjJtrostomimi die 

 within two hours. Crustacea are more resistant, some — Oypris and 

 Dajjhiia especially— requiring as much as 1 part copper sulphate to 

 10,000 of water to kill them. Mosquito larvie die at a concentration 

 varying from 10,000 to 200,000. 



Quoting the results of other experimenters, Devaux" found that 

 both phjenogams and cryptogams were poisoned by solutions of copper 

 diluted to the ten-millionth part or less; Coupin ^' that 1 part copper 

 sulphate to 700,000,000 of water was sufficient to affect the growth of 

 seedlings when applied to their roots and that this is the most inju- 

 rious of the heavy metal salts tested by him; Deherain and De Moussy " 

 that the development of the roots of seedlings was arrested in distilled 

 water containing the slightest trace of copper, and they conclude from 

 this that higher plants during germination, as well as fungi and algse, 

 are extremely sensitive to copper; Bain's experiments'' indicated that 

 1 part of metallic copper to 25,000,<)00 of water was fatal to apple seed- 

 lings in one day; on the other hand, according to iiaulin,' copper chlo- 

 ride does not injure Sterigmatocystli-' until a concentration of 1 to 210 is 

 reached, although silver nitrate is toxic at 1 to 1,600,000. 



In dealing with alg^e, the toxic concentration varies greatly for dif- 

 ferent genera, even for different species in the same genus. Nageli^ 

 demonstrated the extreme sensitiveness of Spirogyra nitlda and 8. 

 dubia to the presence of copper coins in the water. OsciUatoria, 

 Cladophora^ CEdogonium^ and the diatoms succuml) in six hours 

 to a copper sulphate solution of 1 to 20,00<), and in two days to 1 to 

 50,000, according to Bokorny.s' Galeotti^' tinds that a concentration 

 between 1 to 6,300,000 and 1 to 12,600,000 is sufficient to kill Spiro- 

 gyra nitida in two days, and that the so-called colloidal solutions at 1 

 to 6,300,000 are fatal in the same length of time; while in the experi- 



«Devaux, Compt. Rend., 132: 717. 

 feCoupin, Compt. Rend., 132: 645. 

 c Deherain and De Moussy, Compt. Rend., 132: 523. 

 <^Bain, Bull. Agr. Exp. Sta. Tenn., April, 1902. 

 ^Eaulin, Ann. des Sc. Nat. Bot., 5" Ser., II: 9.3. 



.fNiigeli, Ueber oligodynamische Erscheinuugen in lebenden Zellen. Neue 

 Denkschr. d. schweizerischen Gesellsch. f iir die gesammten Naturwiss., 33: 51. 

 r/Bokorny, Arch. f. d. ges. Phys. d. Mensch. u. Tliiere, 64: 262. 

 /'Galeotti, Biol. Centralbl., 21: 321. 



