12 LEAD ARSE NATE. 



from the analyses of these samples that if they were made up accord- 

 ing to this formula there would be in some cases eight times as much 

 arsenic applied as in others. As a consequence the spraying might 

 be condemned as inefficient in certain cases, owing to too weak an 

 application, while in others, using the very same formula, severe 

 injury to the tree might result from too strong an application. An- 

 other and even more serious condition may result from a high per 

 cent of soluble arsenic, due to the lead arsenate being carelessly or 

 improperly made. Where sufficient care is exercised in the making 

 the soluble arsenic should certainly not exceed 0.75 of 1 per cent, 

 calculated as arsenic oxid (As 2 O 5 ) on a 50 per cent moisture basis, or 

 1.5 per cent on a moisture-free basis. 



Lead arsenate should be packed in air-tight packages, in order to 

 keep it in a moist condition until ready for use. After it has once 

 been dried it is much more difficult to keep it in suspension during 

 spraying, which often results in an unequal application. This is 

 the main reason for putting it up in a moist condition instead of in 

 the dry state. Forty to fifty per cent of moisture is sufficient to 

 preserve it in good condition, if it is kept in air-tight receptacles 

 until used. In case a package is opened and only partly used, that 

 remaining may be held over in good condition for the next spraying, 

 by covering it with an inch or more of water. Lead arsenate should 

 always be bought in original packages, which are plainly labeled; 

 when purchased from a broken package, more or less risk is run of 

 not getting true lead arsenate. Three instances have been found in 

 which supposed "lead arsenate" was purchased from drug stores, 

 which on analysis proved to be white arsenic (arsenious oxid). The 

 result of spraying this material on the peach or any other fruit tree 

 would be disastrous. 



While some of the firms are making a good product, this can not be 

 said of all. It was not to be expected, however, that a perfect product 

 would be produced in all cases, especially as the material has not 

 been manufactured until recently and evidently some have taken 

 up the business without proper knowledge of the subject. The 

 product will no doubt be improved as its use and preparation become 

 better understood. 



II. " HOME-MADE " LEAD ARSENATE AND THE CHEMICALS 

 ENTERING INTO ITS MANUFACTURE. 



INTRODUCTION. 



As has been previously noted, arsenate of lead was first proposed 

 as an insecticide in 1892, but it was several years before it was used 

 to any great extent. This was not a product that could be obtained 

 on the market at that time and it was therefore necessary for those 

 using it to prepare their own supply. These conditions no longer 



