8 



MASS. EXPERIMENT STATION BULLETIN 303 



of themselves; but with gas Injury resulted in all instances. An acid 4-X-50 

 mixture in one experiment was safe of itself but caused severe injury with gas; 

 in another experiment injury was severe both from the spray itself and with gas. 

 When a neutral mixture was employed, slight injury resulted from the spray 

 in one experiment and none in another; but gas in both instances either caused or 

 increased the degree of injury. In one instance a 4-X-50 mixture, containing 

 sufficient excess of sodium carbonate to give an alkaline test with litmus, caused 

 severe burning of itself, and the plants were killed after exposure to gas. 



The results with Burgundy precipitates show that the degree of injury follow- 

 ing gas is not correlated with any particular reaction of the spray used. The 

 unstable character of this precipitate even in the absence of gas i^ a sufficient 

 hazard to discourage Its use on greenhouse cucumbers. 



Table 2. The Effect on Cucumber Plants of HCN Gas Follov^^ing 



Treatments with Sal Soda and Caustic Soda Bordeaux Mixtures, 



AND Determinations of Soluble Copper in the Residue. 



'injury in one case; no injury in two. 



'Slight injury in one case; no injury in one. 



•Injury or slight injury in two cases; no injury in one. 



'Injury in two cases; no injury in one. 



'Injury in one case; no injury in four. 



*L race of soluble copper in one case; none in one case. 



Sodium Hydroxide with Copper Sulfate 



In Table 2 is shown the effect of hydrocyanic acid gas on plants spra}-ed with 

 sodium hydroxide and copper sulfate in different ratios. When acid 4-X-50 mix- 

 tures of caustic soda and copper sulfate were employed, injury resulted from the 

 spray itself in two of three instances. In the third case Injury resulted only after 

 exposure to gas. A neutral mixture was used In five experiments, the spray itself 

 causing injury in only one case, but injury resulting from the use of gas in each 

 case. Where alkaline mixtures of 4-X-.'^0 and 4-2-50 ratios were used, injury 

 followed exposure of the sprayed plants to gas, but no injury occurred without 

 gas. 



It may be stated that mixtures prepared from sodium hydroxide and copper 

 sulfate, irrespective of the reaction of the spray, are not safe with HCN on cucum- 

 bers, and It Is concluded that the ratio of sodium hydroxide to copper sulfate 

 does not materially influence the degree of injury. 



