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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 15 



and cites experimental data where sodium sulphate and particularly 

 sodium chlorid had acted as a solvent for lead arsenate. 



Hayward & McDonnell reported experimental data showing "that 

 lead arsenate applied in water containing twenty parts of chlorin per 

 million had caused more injury to peach foliage than when applied 

 with distilled water, and that the addition of 10 to 40 grams of sodium 

 chlorid or sodium carbonate per gallon had caused a heavy increase 

 in arsenical injury." The usual reaction between acid lead arsenate 

 and chlorin is the formation of a soluble arsenate and a complex lead 

 salt. The sodium arsenate goes into solution readily in atmospheric 

 moisture, and is then absorbed by the plant and causes burning. 



To determine what salts are present and their proportions in waters 

 with varying degrees of hardness, the following analyses were made of 

 typical water samples. 



T.4BLE IV. — An.\lyses of Soft and Hard Waters 



Hypothetical Combinations of Above Analyses 



^The amount of soap solution used in neutralizing the hardness of the three sam- 

 ples is, — (1)4. 9, (2) 6. 7, (6) 14. 0. 



It will be noted that the chlorin content of only the first one is 

 less than twenty parts per million — the factor which was associated with 

 arsenical injury in Hayward & McDonnell's experiments. 



All hard waters do not necessarily contain chlorin, but they may 

 have excessive quantities, as already mentioned, one of the common 

 forms in which chlorin occurs is sodium chlorid, which is a character- 

 istic component of saline rather than that of hard waters. A study 

 of eighty analyses of California waters showed that only 14.8% of 

 the total were apparently safe for use with acid arsenate of lead, when 

 applied to tender foliage. These samples cannot be considered as 

 typical because there is usually some suspicion regarding a water be- 



