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BULLETIN 1147. U. S. DEPARTMENT OE AGRICULTURE. 



Table 11. — Arsenic on potato leaves sprayed with arsenicals with and without the addition 



of lime. 1 



Sample 

 No. 



Material used. 



Total 





arsenic 



Arsenical 



oxid 



used 



(As 2 5 ) 



per 10 



in drv 



gallons. 



arsenical. 





Per cent. 



Ounces. 



49.40 



2 



49.40 



2 



32.76 



3i 



32.76 



H 



»41.49 



2i 



79.60 



2J 



55.00 



2 



55.00 



2 



55.00 



2 



42.80 



2i 



42.80 



2* 



42.80 



2i 



Arsenic 



(As) 

 on dry 

 leaves. 



24 

 24A 



40 



40A 



23 



S6 



87 



S7A 



S7B 



ss 



88A 



SSB 



Calcium arsenate 



Sample 24 plus lime (2 ounces) 



Acid lead arsenate 



Sample 40 plus lime i^2 ounces) 

 Zinc arsenite 



Calcium meta-arsenate 



Calcium arsenate 



Sample s7 plus lime (2 ounces) 

 Sample S7 plus lime (4 ounces) 

 Calcium arsenate 



Sample SS plus lime (2 ounces) 

 Sample SS plus lime (4 ounces) 



Parts per 

 million. 

 240 

 340 

 530 

 580 

 540 

 830 

 290 

 270 

 290 

 360 

 280 

 380 



1 Equal percentages of AS2O3 and AS2O5 were used for all the sprays. 

 ' As 2 3 . 



During the season of 1920 potato plants were sprayed at Arlington, 

 Va., using (a) dry acid lead arsenate, (b) dry " suspender" 7 acid lead 

 arsenate, (c) zinc arsenite, and (d) Paris green. The sprays were 

 made to contain the same percentage of arsenious or arsenic oxid and 

 were applied four times during the season, using a power sprayer. 

 Nine duplicate sets of 50 leaves each were collected on the same days 

 throughout the season from each plot of the various sprayed vines. 

 These leaves (900 in all from each plot receiving a different spray) 

 were anal}~zed for arsenic, with the following average results, ex- 

 pressed as parts of arsenic per million of dried potato leaves: Paris 

 green, 155; "suspender" acid lead arsenate, 195; zinc arsenite, 203; 

 and acid lead arsenate, 210. 



The physical properties of arsenicals have been studied to some 

 extent since the time they were first prepared, but no complete study 

 has been reported. This may be due in part to the difficulties 

 encountered m measuring those physical properties which contribute 

 toward making a satisfactory product for dusting or spraying. 

 Wilson (53) in 1919 gave data on the burning, suspensibihty, and 

 adhesiveness of Paris green, zinc arsenite, acid and basic lead arse- 

 nates, and calcium arsenate. 



A series of tests was performed, using commercial powdered arsen- 

 icals (Table 12), to obtain comparative data on the apparent density 

 and suspensibihty of these products. The apparent density of a 

 powder here described is based on the number of grams occupying 

 a volume of 1,000 cubic centimeters and the suspensibihty on the 

 volumetric readings of 30 grams of powder which had settled after 

 having been shaken for one minute with approximately 500 cubic 

 centimeters of water and having stood for 10 and for 60 minutes. 



7 "Suspender" lead arsenate is a trade name applied to a powdered lead arsenate containing some added 

 organic substance for the purpose of keeping the arsenate in suspension when mixed with water. 



