Volume 1

Some experiments on larvicides / Ronald Ross and E.S. Edie.

  • Ronald Ross
Date:
1911
Catalogue details

Licence: Public Domain Mark

Credit: Some experiments on larvicides / Ronald Ross and E.S. Edie. Source: Wellcome Collection.

    7/10 page 389
    One part cyanide in 58,000 of water killed all the larvae in three and one-third hours. One part cyanide in 106,000 parts of water killed all the larvae in five hours. In another experiment with nearly the same strength (one in 110,000), all the larvae except two were killed in five hours, the last two living about seven and a half hours. One part cyanide in 240,000 parts of water killed all the larvae in the course of a night (less than sixteen hours from the time the cyanide was added). One part cyanide in 303,000 parts of water killed about 50 per cent. of the larvae in six and a half hours, and all except one in twenty-two hours. We have not carried out any experiments with weaker solutions of potassium cyanide than last mentioned, as we did not consider it advisable to use solutions in which larvae can live for a longer period than about eighteen hours, and a solution of one part cyanide to 300,000 parts of water was found by repeated experiment always to satisfy this condition, though in some cases individual larvae survived about twenty-four hours. We have tried the effect of a solution containing one part potassium cyanide to 300,000 parts of water on two lots of Anopheles larvae, and in both cases about 80 per cent. of the larvae were killed in less than eight hours, and the rest in from twelve to fifteen hours. Strychnine in dilutions greater than one in 50,000 parts of water appeared to have no effect on larvae. As we had obtained much more satisfactory results with potassium cyanide we did not try solutions of strychnine stronger than the above. We have been unable to discover any other substance whose potency as a larvicide approaches that of potassium cyanide. This compound also possesses the advantage of being easily carried about and of being comparatively cheap. Its one drawback. lies in the fact that it is extremely poisonous, and it is apt to undergo partial hydrolysis with the production of a certain proportion of free prussic acid. | On the other hand the use of potassium cyanide can be restricted to stagnant water which is not used for drinking purposes, while
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