4 
BULLETIN No. 77b. 
I_Cause of Injury to Foliage from Arsenites and its 
Prevention. 
It seemed to be the belief of horticulturists and entomologists that 
the “burning” or “scorching” of foliage when sprayed with arse¬ 
nites was due to soluble arsenic compounds, though no results had 
been published to show definitely that such was the case. To test 
this point,mixtures in the proportion of 1 pound each of White arsenic, 
London purple and Paris green,separately, in 100 gallons of water, Bor¬ 
deaux mixture, kerosene emulsion, Lau celeste, and other solutions, 
were made. After standing twenty-four (24) hours a portion of the 
the mixture was drawn off and tested qualitively. for soluble arsenic 
compounds, and at the same time ‘another portion was applied to 
foliage and the effect noted. In no case was injury noticeable where 
soluble arsenic was absent, but in all cases it was proportional to the 
amount of soluble arsenic. Seeing in this experiment the insolu¬ 
bility of the arsenites in Bordeaux mixture, and the consequent 
exemption of foliage from injury, and knowing that London purple 
was, in the main, an arsenite of calcium, being produced by the 
decomposition of rosaniline arsenite by calcium hydrate (lime m 
solution), it was at once plain, from a chemical point of view, that 
lime would render the soluble portion of the arsenites insoluble in 
water, and thus render foliage free from injury from them. Various 
mixtures of an equal weight of pure lime (GaO) and White arsenic, 
London purple, and Paris green, separately in water, Mere made to 
test this point. Some of the mixtures contained as much as four 
pounds of arsenite in 100 gallons, but in only a few cases was so 
much as a trace of soluble arsenic found, when tested by sulphur¬ 
etted hydrogen. 
To bring out the above, experiments were conducted and quanti¬ 
tative determinations of soluble arsenic made at the time mixtures 
were applied to foliage. I lie results are given in tabulated foim in 
Table I: 
