-3- 



Somo Rront Eulletina 



Establishing and Managing Young Apple Orchards, U.S.D.A. Farmers' Bui. 



IIo. 1897. 

 Control of Grape Diseases ajid Insects in Eastern United States. U.S.D.A. 



Farmers ' Bui. No. 1393. 

 Diseases of Strawberries. U.S.D.A. Farmers' Bui. Ko. 1891. 

 Harvesting and Handling Cultivated Cranberries. Fanners' Bui. No. 1882. 

 The Home Fruit Garden, U.S.D.A. Leaflet No. 218. 

 Victory Gardens. U.S.D.A. Misc. Pub. No. 483. of 



Investigations on the Cause & Control of Biennial Bearing/^pple Trees. 



U.S.D.A. Tech. Bui. No. 792. "" 



Storage of Vegetable Seeds, U.S.D.A. Leaflet No. 220. 



Factors V/l-iich Affect the Vitamin C Content of Apples. Va. Tech. Bui. 69. 

 Baits and Bait Traps in Codling Moth Control. Va. Bui. 320. 

 Substitutes for Nitrogen Fertilizers in Orcharding. Mo. Circ. 236. 

 Factors Affectiiig Size 5: Color of Fruit. Mo. Bui. 428. 

 Studies of Bitter Pit of the Apple. Cornell llemoir 234. 

 Control of ViThito Grubs in Strawberries, Cornell Bui. 770. 

 Questions and Answers on Fruit Culture. S. Dak. Circ. 35. 

 Influence of Spacing on Yield and Grade of Strawberries. R.I. Bui. 283. 

 Locker Freezing of Fruits and Vegetables, ViTash. Popular Bui. No. 161. 

 (Certain state bulletins may involve a small charge.) 



SOlV i E FACTS ABOUT LE AD ARSENATE 



(This article was prepared by L. G. Gemiaell of the Agricultural 

 Insecticide and Fungicide Association. -- Continued from the June issue.) 



Meth od of Productio n. Today, almost v.dthout exception, commercial 

 Lead Arsenate is ms^de by adding arsenic acid to litharge (PbO), a reddish 

 yellow lead compound made by roasting metallic lead. In order to insure 

 complete reaction, the mixture is kept constantly stirred and the resultant 

 slurry of Lead Arsenate and water is carefully checked by control chemists 

 who analyze it in this stage so that by careful acid addition and close con- 

 trol of the temperature of the reaction, a product results v^hich v;hen filtered, 

 dried and ground will be about 98/^ pure, and contain in excess of 32^;^ arsenic 

 pentoxide. In recent years by industry agreement a red dye has been added 

 to the Lead Arsenate while in the wet state so that aftor processing the prod- 

 uct will in no way resemble an edible powder such as flour or pov/dered sugar. 



The Lead Arsenate slurry, checked by the laboratory, is fed by 

 gravity or pumps to the drying apparatus which may be in any one of several 

 forms. One common type is the rotary or drum drier where a coat of the 

 thickaned Lead Arsenate paste is picked up on the outside of a steair heated 

 slov.ly revolving cylinder. At the completion of one turn of the cylinder 

 the Lead Arsenate from virhich the water has now been evaporated is scraped 

 from the drum and in dry povirdered form is passed to a grinding mill or pul- 

 verizer before packaging. In other t;^Tpss of driers part of the wat:r con- 

 tained in the Lead Arscr.ate slurry is removed by f^uoh .i.nenhr-nical meojis as 

 filter presses or centrifuges. In this method Goluble saibf; racy be washed 

 out before transfer of the partly dried material to the stsani heated drying 

 ovens. As in the previous case, the dried material is further ground before 



