28 S. E. A. McCallan 



ever, he did not consider that this amount of copper exercised any fun- 

 gicidal action, except possibly as a secondary effect in the case of very 

 sensitive fungi, though he conceded that it probably was a factor in spray 

 injury. 



Schander (1904) does not believe that atmospheric agencies are ordi- 

 narily very effective. He placed various bordeaux mixtures in crystal- 

 lizing dishes, one lot being exposed to the sun and the other kept in the 

 shade. Both lots were periodically moistened with rain water. Soluble 

 copper appeared in neutral bordeaux after 23 days, but in alkaline bor- 

 deaux not until 42 to 56 days. Butler (1914:142), however, questions 

 the trustworthiness of Schander's test for soluble copper. 



Crandall (1909) performed extensive field tests with apple trees sprayed 

 with bordeaux mixture. The trees were either exposed to the rain and 

 dew, or wetted with cistern water, carbonated water, or distilled water, 

 and the drip was collected and analyzed for soluble copper and alkalinity. 

 The freshly made bordeaux mixture contained no free copper. The drip 

 waters did not give a neutral reaction until late in the summer, but soluble 

 copper was present from the first and continued as long as any bordeaux 

 was present, thus attesting to the slow rate of solubility of the copper 

 from bordeaux mixture. Rain water and carbonated water were equally 

 effective in bringing copper into solution. Cistern and distilled water 

 were only about half as effective. The amount of soluble copper present 

 was from a trace to 1 part in 11,000 parts of water. Excess lime dimin- 

 ished the extent of the solubility of the copper, but did not entirely 

 prevent it. Limited laboratory experiments, however, gave contra- 

 dictory results. Bordeaux mixture in crystallizing dishes, either dry or 

 intermittently wet with cistern water, gave no soluble copper at the end 

 of 65 days. Nor did sprayed trees, also either dry or frequently moistened 

 with cistern water, show any copper in the wash waters at the end of 54 

 days. Crandall (1909:226) concludes " that meteoric waters possess 

 solvent powers that do not belong to the water artificially applied." He 

 assumes that the CO2 is the chief dissolving agent, but that it is probably 

 supplemented by other agencies, possibly ammonium compounds, nitrates, 

 and nitrites. 



Pickering (1907, 1909), and Bedford and Pickering (1910), undertook 

 numerous laboratory experiments in an effort to demonstrate the solvent 

 action of the CO2 of the atmosphere. Carbon dioxide was passed through 

 suspensions of the various basic sulfates of copper, the length of time 

 required and the amount of copper brought into solution being noted. 

 Copper from the Woburn bordeaux (4CuO, SO3) was found to be im- 

 mediately soluble, while in the case of ordinary bordeaux (IOC11O, SO3, 

 3CaO) there was a considerable delay. Pickering states that this delay 

 is due to the presence of excess lime. The C0 2 carbonates the lime most 



