254 



THE CANADIAN HORTICULTURIST. 



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Memorandum re Addition of Sal Soda to Paris 

 Qreen Mixture. 



In answer to the enquiry "can sal soda 

 be used instead of lime in the preparation 

 of paris green mixture ? " the followingf in- 

 formation is submitted : — 



When paris green mixed with water (at 

 the usual rates i lb. to 100-200 gallons) is 

 applied to certain classes of delicate foliage 

 (as of stone fruits) a corrosive or "burning" 

 effect has been noticed to follow, the leaves 

 showing decided marks of injury as the in- 

 secticide dried upon them. This injurious 

 effect may be entirely overcome by the ad- 

 dition of a small quantity of lime, the usual 

 quantity advised being i lb. to each i lb. of 

 paris green, though this is probably much 

 more than is absolutely necessary. 



Sal soda (more commonly known as 

 washing soda) should chemically effect the 

 same purpose as the lime, though in the 

 apparent absence of recorded experimental 

 data it would not be wise to generally ad- 

 vise the substitution. Arsenate of soda, as 

 is well known, is more or less injurious to 

 foliage, but the compound formed in the 

 mixture under discussion would rather be 

 arsenite of soda, regarding the action of 

 which on foliage I cannot find any reference. 

 I, however, am of the opinion, drawn from 

 a general consideration of the whole subject, 

 that lime would be better, or rather, safer to 

 use, since the lime-arsenic compound is un- 

 soluble, while the soda-arsenic compounds 

 are easily soluble in water and hence more 

 likely to affect the foliage. 



To obtain the neutralizing effect of i lb. 

 of slaked lime, approximately 4 lbs. of ordin- 

 ary crystallized washing soda would be re- 

 quired. This quantity of lime, however, as 

 already pointed out much exceeds that ab- 

 solutely necessary, and most probably 2 lbs. 



of washing soda (equivalent to yi lb. of lime) 

 would be ample. An experiment recently 

 made in our laboratories showed that when 

 4 lbs. of sal soda were added to a mixture 

 of I lb. of paris green in 160 gallons of 

 water, considerable traces of arsenic went 

 into solution ; in other words, that there 

 had ceen a slight decomposition of the paris 

 green. When, therefore, through inability 

 to conveniently obtain lime, sal soda is sub- 

 stituted, we should advise not more than 2 

 lbs. to each pound of paris green in the 

 spraying mixture ; but in view of the general 

 results of soluble arsenic compounds on 

 foliage, and in the absence of any definite 

 data from spraying experiments with the 

 mixture under discussion, it would be safer 

 to use lime whenever possible. The arsen- 

 ate of lime that may be formed in the fluid 

 from following this course has been shown 

 to be non-injurious to foliage and an ex- 

 cellent insecticide. 



Perhaps it may be pointed out that when 

 paris green is used in bordeaux mixture, 

 there is no need for further addition of lime 

 or other alkali to prevent injury to foliage, 

 and that in this mixture both the fungicidal 

 and insecticidal properties are unimpared. 

 Frank T. Shutt, Chemist. 



Dominion Experimental Farms. 



The Sweet Chestnut. 



Under notes and comments m the May 

 number of the Horticulturist, I see you ask 

 for information regarding the hardiness of 

 the sweet chestnut in the north. 



I have grown them here in nursery rows 

 for the past 25 years ; have 50 of them per- 

 manently set out and in bearing, and have 

 proved them to be perfectly hardy, the frosts 

 of all these years never having injured even 

 a single tip of any of the thousands of the 



