CYANIDING. 40 



by which every pest can be killed more surely than by 

 any other method. Ked Spider even has been said by 

 some users to succumb to its effects, but it is still a ques- 

 tion to many if this adamantine pest can really be suc- 

 cessfully treated on tender isubjecte, such as vines. A 

 very strong application, sufficient to kill Mealy Bug, can 

 be made while the vines are dormant; but at this time 

 the Red Spider is also dormant, and exceedingly hard to 

 kill, being well hidden in cracks in the woodwork and 

 under the bark of the vices . 



" On growing plants great care is necessary in the appli- 

 cation of the remedy. The temperature of the houses 

 must be as low as 50 degrees, and the plants dry and free 

 from drops of moisture on the leaves. The evening is 

 the best time, as strong light is not desirable during the 

 operation. The ventilators of the houses to be operated 

 upon must be capable of being opened from outside, as 

 the gas is a most deadly poison. Nobody must on any 

 account enter the house whilst the fumigation is going on. 

 It is most important that all chemicals used in the pre- 

 paration of the gas shall be of known strength, and be 

 obtained from reliable firms. 



" The Chemicals Used are a double salt of potas- 

 sium and sodium cyanide, 98 to 100 per cent, purity, and 

 sulphuric acid of specific gravity 1.8. The former chemi- 

 cal is often called sodium cyanide 130 per cent. This 

 has been used to denote the fact that the strength of the 

 above-mentioned double salt, as compared with potassium 

 cyanide of 98 per cent, purity, is as 130 to 100. That is, 

 if loz. of potassium cyanide 98 percent, would be required 

 to fumigate a certain space, only foz. of the 130 per cent, 

 sodium cyanide would be required to do the same work. 

 Now potassium cyanide is made in strengths varying from 

 30 per cent, to 98 per cent., so that unless the exact 

 strength is known, and the quantity required calculated 

 on this basis, serious damage might be done to the plants. 

 On the other hand, this double salt of sodium and potas- 



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