164 EXPEKIMENT STATION RECORD. 



arsenate on foliage. These were conducted particularly for the purpose of de- 

 termining by what solvent the lead arsenate is acted upon that renders more 

 or less of the arsenic soluble so that burning of the foliage results. 



During the investigations in 1907 no injury resulted to the foliage of the 

 apple from any of the mixtures applied and only very slight injury to that of 

 the peach, none being of a decided enough character to attribute it with cer- 

 tainty to the spraying. Similarly in 190S, the foliage of the apple trees was not 

 injured in any case from applications of pure lead arsenate or any of the by- 

 products naturally formed in its manufacture. " Rather severe injury was 

 caused to the foliage and fruit of the peach by pure lead arsenate, made either 

 from lead acetate or lead nitrate, and the same was true when the salts formed 

 as by-products in the making were not washed out, whether applied with or with- 

 out lime. The fruit was of a deep red color which generally extended throughout 

 the flesh, and maturity was hastened about one week. Lead nitrate caused 

 severe injury to the foliage but not to the fruit. Lead acetate in the stronger 

 application caused slight injury to the foliage, but very materially protected the 

 fruit from insect injury. Sodium acetate and acetic acid, acetic acid alone, and 

 sodium nitrate produced no injurious effect on the foliage or fruit in the 

 strengths applied. . . . No injury from previous spraying could be detected 

 on May 25. when the final application was made. Five hot, clear days, without 

 rain, followed this application, and on June 4, 10 days after the application, 

 very decided injury was observed." Thus it appears that during the years 

 1907-8 no injury resulted to apple foliage from 3 applications of lead arsenate, 

 made from sodium arsenate and lead acetate, or sodium arsenate and lead 

 nitrate, when applied at the rate of 1^ lbs. (dry basis) to 50 gal. of water. 



Lead arsenate prepared from lead nitrate possesses several qualities which 

 make it slightly more desirable for spraying purposes than that prepared from 

 lead acetate, but it is more dangerous to use if not properly made. " In very 

 minute quantities arsenic appears to exert a stimulating effect or act as a 

 tonic [on foliage], as it does on animals. It is probably this action which, by 

 accelerating the functional activity of the leaf and producing more rapid 

 assimilation, causes the excessive re^ldening and hastens the maturity of the 

 fruit. On the other hand, if too large an amount is absorbed, it has a toxic 

 effect. I'esulting in retarded assimilation, which in turn will cause the fruit to 

 shrivel and drop before it has matured." 



In experiments to determine the action of the carbon dioxid of the air, lead 

 arsenate was found to be slightly less soluble in distilled water saturated with 

 carbon dioxid, even when heated to 50° C, than in cold distilled water free 

 from carbon dioxid, and it would hardly be expected that the results could be 

 otherwise on the tree. A large amount of arsenic was dissolved by solutions 

 of sodium chlorid and sodium carbonate, and also by a sample of water tested. 

 " It would appear from these results that if certain salts commonly occurring 

 in waters are present in more than very small amounts they will exert a solvent 

 action on the lead ai'senate." 



Still more exhaustive orchard experiments than those here reported were con- 

 ducted in 1909 in which lead arsenate was applied to peach trees in the same 

 proportions as in other experiments [IJ lbs. (dry basis) to 50 gal.], 3 applica- 

 tions being made. These are briefly summarized as follows: "When applied 

 with spring water . . . some injury to foliage resulted, but it was not nearly so 

 marked as in the precetling year, and a longer time elapsetl before the injury 

 was noticeable. When applied with distilled water very slight injury occurred, 

 noticeably less than when the spring water was used. When applied with 

 distilletl water to which 10 grains per gallon of sodium chlorid had been added, 

 rather serious injury resulted. When distilled water containing 40 grains of 



