283 



should the demand for them arise. The preparation of " Antinonnin," 

 un ortho-cresol into which two nitro groups have been introduced and 

 prepared on the analogy of benzene nitro compomids which are known 

 to be insecticidal, is cited as an example of the value of systematic 

 research as opposed to empirical methods. Ehrlich's researches on 

 the effect of the position of the arsenic in the molecule led to the 

 ])roduction of the famous " 606," highly toxic to blood parasites and 

 ])ractically innocuous to the host. There is no great difficulty in 

 preparing a number of excellent insecticides when cost of production 

 is no object. The use of cupric-di-methanal-di-sulphite Cu (HgC. 

 OH.SO;,)„, which is easily prepared by passing SO^ into a suspension 

 of copper liydroxide in 40 per cent, formalin, has been suggested. 

 A clear blue solution containing 3 per cent, of copper is obtained, 

 and it is claimed that it combines in itself a copper insecticide and a 

 sulphuring agent. The probability exists that many insecticides 

 operate by providing the material for the liberation of minute quantities 

 of a compound in the nascent state and a solution of /5 naphthol in 

 caustic soda can be so adjusted that a mere trace of CO.^ will precipitate 

 a minute quantity of fi naphthol. The value of potassium sulphide 

 probably depends on the slow precipitation of minute particles of 

 sulphur, and solutions yielding exceedingly finely divided sulphur 

 under the influence of mere traces of CO^ can be prepared. Copper 

 may be combined with paraffin by dissolving copper resinate in mineral 

 oil. If the mere suffocation of an insect by blocking its breathing 

 orifices be desired, it is suggested that " viscose," a derivative of 

 cellulose, might be tried. Great stress is laid on the importance of 

 the physical condition of the remedy used in relation to its efficiency, 

 emulsions generally having a much higher bactericidal power than 

 solutions. The use of an emulsified oil in conjunction with sodium 

 arsenite for tick eradication enabled a much lower strength of arsenite 

 to be used with equal effects and at the same time removed all danger 

 of killing cattle by scalding, a not infrequent accident. In conclusion 

 it is urged that the Entomologist and Chemist should join forces, the 

 former to investigate and discover what is best to be done and the 

 latter to devise the means, so far as possible, under the given conditions. 



Lefroy (H. M.). Insecticides. — Ann. App. Biol., London, i, nos. 3 & 

 4, January 1915, pp. 280 298. 



There is a fashion in insecticides. At one time Paris green and 

 London purple ruled ; then came lead arsenate in America ; this 

 is apparently giving place to zinc arsenite and barium arseiiite, 

 while there is reason to hope that lead arsenate, and perhaps lead 

 chromate, will become more familiar in this country. In America, there 

 was an era of paraffin enuilsions and resin washes ; then came whale 

 oil soap ; lime, salt and sulphur followed ; then the heavy oils and 

 then " miscible oils." Lvsol and similar mixtures are in use on the 

 Continent and miscible oils are being used more freely in Australia 

 and South Africa. The author quotes the insecticides recommended 

 (hiring 16 consecutive weeks in the Gardeners' Chronicle in 1913, the 

 leaflets of the Board of Agriculture and information from general 

 sources, reports, etc., and fijids that the following are the methods in 

 fairly general use. (1) Lead arsenate or Paris green for caterpillars. 



