1921.] 



Insecticides and Fungicides. 



631 



British Pharmacopaea 1914 for sulphurated potash; and shall 

 contain not less than 42 per cent, nor more than 45 per cent, 

 of sulphur as determined by the process prescribed in the 

 British Pharmacopaea for the estimation of sulphur in sul- 

 phurated potash. 



Note. — Liver of sulphur is now used less often than formerly, but 

 nevertheless those who do purchase it should obtain the potassium salts as 

 defined above and not the cheaper sodium compounds. This remark does not 

 imply any comparison between the values of the potassium and other 

 sulphides for spraying purposes, but is merely to point out that if a purchaser 

 is paying for an article, he should be supplied with it and not with something 

 else, which perhaps costs less to manufacture. 



7. Sodium and Potassium Cyanides. — (a) An article sold as 

 sodium cyanide for agricultural and horticultural purposes shall 

 be capable of evolving (when treated with an acid) not less 

 than 56 per cent, of its weight as hydrocyanic acid. 



{h) An article sold as potassium cyanide for agricultural and 

 horticultural purposes shall be capable of evolving (when 

 treated with an acid) not less than 43.7 per cent, of its weight 

 as hydrocyanic acid. 



Note. — In fumigating with hydrocyanic acid gas it is of the utmost 

 importance that the dose shall be accurately calculated, and this of course is 

 impossible unless the purchaser can obtain the "cyanide" practically pure. 

 Purchasers should therefore insist on a guarantee in accordance with the above 

 requirement. Sodium cyanide is almost invariably used, as it is cheaper and 

 weight for weight gives off more gas than the potassium cyanide. The latter 

 is included, however, in case any should still prefer it. 



8. Formaldehyde. — This substance is not at present within 

 the scope of the proposed legislation, but it is desirable that it 

 should receive mention here on account of its increasing 

 popularity as a dressing for cereals against bunt, &c. Formal- 

 dehyde is often referred to as " formalin," which was originally 

 the trade name applied by a German company to a 40 per cent, 

 solution of formaldehyde. It is important now that under 

 whatever name formaldehyde is bought a guarantee should be 

 obtained as to the percentage of formaldehyde in the solution 

 supplied. 



