Cyanide Gas Remedy for Scale Insects. 439 



Many fiuuigation covers have been entirely iviiued by storage in 

 contact with jars of acid or on a floor where acid has' been spilled. Many 

 more liave been damaged by being handled with hands fouled with 

 acid. It pays to take care to avoid such accidents. The men who 

 measure out the acid and dose the trees and attend to generating 

 vessels had best not even touch the covers before washing and drying 

 theii' hands. 



llic Gcneraimrj Vessel. — The vessel in which the chemicals are 

 mixed had best be rounded and somewhat narrowed at the bottom 

 inside, as it is necessary that the acid-water mixture be deep enough 

 to cover the lumps of cyanide. China pudding-basins and chinii 

 bedroom utensils make as good generating vessels as are commonly 

 procurable in this country. Enamel dishes are excellent until the 

 enamel chips, which quickly happens if the quality is not of the 

 best. A cover or very loose-fitting lid is desirable to check the direct 

 ascent of the gas and to stop minute splashes of acid that otherwise 

 may soon burn innumerable tiny holes in the cloth ; a bottomless 

 parafhn tin with large perforations in the sides is often very suitable. 

 A large coffee-cup will answer as a generaiing dish for a half-ounce 

 charge, and a quart pudding-basin for a two-ounce charge, while for 

 a ten-ounce charge a vessel that will hold about a gallon is needed. 

 Jug-shaped glazed earthenware generating vessels, patterned after 

 those commonly used in California, may now be procured made-to- 

 order from the Trent Potteries Ltd., P.O. Box 1825, Johannesburg 

 (works at New Muckleneiik, Pretoria), and from Consolidated Rand 

 Brick, Pottery, and Lime Co., Olifantsfontein. The cost is about 

 Ts. each. 



Improved Methods of Generatiny ike Gas. — The open vessel 

 method of generating the gas under the fumigation cover was almost 

 entirely superseded about six years ago in California by what may be 

 called the cyanofumer method, which, in the past few years, has 

 given way to the use of liquefied hydrocyanic acid gas. South Africa 

 is not ready for the general adoption of either of these improvements, 

 but it is desirable that prospective fumigators should know about 

 them in order that they may consider their applicability to their 

 individual conditions. 



"Cyanofumer" is the name applied to a patented machine 

 generator that is moved from tree to tree, and from which the gas is 

 delivered through a hose. The body of the apparatus consists of two 

 air-tight metal vessels fixed one above the other. In the lower one is 

 carried a large volume of acid-water mixture, and in the upper a 

 large volume of cyanide dissolved in water. By working a pump the 

 exact quantity of the cyanide solution necessary to yield the volume 

 of gas wanted for a tree is run into the acid. The chemicals react 

 at once and the resultant gas is discharged through the hose. The 

 method is free of the risk of damaging the cover by splashing, and it 

 effects economies in the chemicals and labour when there are many 

 contiguous trees to be treated. Three sizes of the machine are manu- 

 factured : the "Junior," holding the equivalent of about 7 lb. of 

 cyanide; the "Standard," the equivalent of about 40 lb.; and the 

 " Jumbo," the equivalent of about 60 lb. Until recently only the 

 Junior was sold outright, the other sizes being leased and a royalty 

 charged in respect of each tree treated; but it is understood that the 



