10 MASS. KXPr-'.RIMKXT STATION BULLETIN 303 



Factory-made basic copper sulfates, the preparation of which is fully reported 

 by Holland et al. (6, 9), caused no injury of themselves or with gas. These sprays 

 are neutral to litmus and were prepared with calcium carbonate, magneisum 

 carbonate, or sodium carbonate. In preparation the heated precipitates are 

 washed practically free of soluble by-products, i.e., magnesium and sodium sul- 

 fates, then dried and air separated. The addition of chemical hydrated lime, 

 in 0.1, 0.2, 0.5, and 1.0 per cent strengths, to diluted 26 per cent basic copper 

 sulfate caused injury with gas which was most severe, generally considered, with 

 the highest amounts of lime added. Corona copper carbonate powders, contain- 

 ing 18 per cent and 50 per cent copper, and basic copper sulfate (Marsh Bros.), 

 containing 53 per cent copper, are neutral to litmus and were also safe with gas. 

 The Corona 18 per cent product is similar in preparation to the 26 per cent basic 

 copper sulfate, and the Corona 50 per cent product to the 53 per cent basic copper 

 sulfate. Greater stability is obtained in the manufacture of basic copper sulfates 

 and carbonates by heating the precipitates, and this appears to explain their 

 safety with HCN. The Marsh Bros, product is produced by the action of Ionized 

 copper sulfate or of sulfuric acid on metallic copper and contains no by-products. 



Stainless Copper Sprays 



This group includes copper acetate (Table 4), Hammond's Copper Solution, 

 Fungtrogen, and copper sulfate. 



Table 4. The Effect on Cucumber Plants of HCN Gas Following 

 Treatments with Certain Stainless Copper Sprays. 



Active Cu Concen- Reaction Reaction Injurj' 

 Fungicide Content tration to for 



Per Cent Litmus Soluble Witliout With 



Copper HCN HCX 



Hammond's Copper Sol 3.04 a Alkaline — — ± 



Fungtrogen 0.47 b .Alkaline — — — 



Ammoniacal Copper Carbonate . . c Alkaline — — — 



Basic Copper Acetate 'MA d Acid + + + 



Norma! Copper Acetate .'U.S e Acid + ± + 



Copper Sulfate .01% Sol Neutral Trace — — 



Copper Sulfate 02% Sol Neutral Trace — — 



Copper Sulfate .03% Sol Neutral Trace — ■ — 



Copper Sulfate .05% Sol Neutral Trace — — 



Copper Sulfate .07% Sil Acid Trace — — 



a — 1-80 in 4 instances; 1-40 (double the manufacturer's recommendation) in one. Slight injury 

 occurred in two cases at the 1-80 concentration: no injury in the other cases. 



b — 1-60 in 3 instances; 1-30 (double the manufacturer's recommendation) in one. 



c— NHiOH 0.8% with CuCOa 0.24, 0.16, and 0.08 % by weight. 



d — 0.2.5, 0.50, and 0.75 % by weight. Injury without HCN in 2 cases; no injury in 4 cases. 



e — 0.25, 0..50, 0.65, 0.75, and 0.80 % bv weight. Injury without HCN in 2 cases; no injury in 3 

 cases. 



Basic copper acetate, containing 34.4 per cent copper, and normal copper 

 acetate, containing 31.8 per cent copper, were used. Both forms gave positive 

 tests for soluble copper and acid reactions to litmus. Basic copper acetate was 

 used at strengths of 0.25, 0.50, and 0.75 per cent by weight, and normal copper 

 acetate at strengths of 0.25, 0.50, 0.65, 0.75. and 0.80 per cent. Since both products 

 contain over 30 per cent of copper, a concentration of 0.25 per cent would contain 

 over 0.07 per cent copper, which would seem fairly reasonable, although references 

 state that they have been used at concentrations ranging from less than 0.1 to 1 



