Entomology for medical officers / by A. Alcock.

  • Alcock, A. (Alfred), 1859-1933.
Date:
1920
Catalogue details

Licence: In copyright

Credit: Entomology for medical officers / by A. Alcock. Source: Wellcome Collection.

    49/404 (page 29)
    but sprays of kerosene, either pure or emulsified with soft soap and water, are more for use outside, petroleum in any form being fatal to insects and their larvae. Fumigation on a large scale is necessary where noxious insects have established themselves in rooms and storehouses. The fumigants commonly employed and everywhere obtain¬ able are sulphur dioxide, and hydrocyanic acid, rarely chlorine. During the operation and for several hours after¬ wards all the doors, windows, flues, etc., of the place under treatment should be kept closed so as to expose the insects, and particularly the resistant eggs and pupae, to the pro¬ longed action of the poisonous gas. It may be necessary to repeat the operation after a short interval, to ensure the destruction of any larvae or adults that have hatched from eggs or pupae that have survived the first attack. The following methods for disengaging the fumes are adequate where no special distributing apparatus is available:— Sulphur Fumigation.—Not less than 8 oz. of sulphur should be used for every 1000 cubic feet of space. The sulphur, broken in lumps and moistened with spirit, is placed in an iron bowl, and the bowl is stood in a basin of water. The sulphur is then ignited and left to burn itself out. It must be remembered that the fumes tarnish metal and have a bleaching action. Fumigation with Hydrocyanic Acid Gas is perhaps more popular with entomologists than with medical men ; it should be undertaken with the greatest caution. Not less than 6 oz. of potassium cyanide and about double the quantity of sulphuric acid are required for every iooo cubic feet of space. The cyanide should be put in a muslin bag, which should be dropped into an open vessel containing the sulphuric acid, at the very moment of leaving the room. This is the method generally recommended; but it is safer —the gas being disengaged less energetically—if instead of sulphuric acid, a solution (in a little water) of 6 oz. of tartaric acid be employed in operations on the small scale. Chlorine Fumigation.—The gas is disengaged by mixing bleaching-powder with water, and if necessary adding a little dilute acid; or by pouring dilute sulphuric acid upon chloride of lime. The gas has powerful bleaching properties.