ArsenicaIv Poisoning oe Fruit Trees. 23 
curring in our soils, especially gypsum which is notably soluble in 
water, serve to prevent the solution of arsenic. The answer to 
this is unquestionably no. For when 500 grams of soil, rich in sul¬ 
fate of lime, were suspended in 2,000 grams of water and allowed to 
stand, some arsenic went into solution. This experiment was made 
three times and the results showed the presence of soluble arsenic 
so decidedlv that there was no reason to seek even for cumulative 
evidence on this point. It does not, of course, matter where the al¬ 
kalies came from, whether they were already in the soil or whether 
they are brought to the soil by the water used for irrigation, some 
of which I know to be rich in alkali. 
CANNOT DISTINGUISH THE SOURCE OE ARSENIC:. 
I do not know the history of the samples of soil examined 
whether they contained the arsenic as lime arsenite or lead ar¬ 
senate, nor does it appear to me to be a matter of importance in 
which form the arsenic was present in the soil. The experiments 
with the alkalies, Glauber’s salt and ordinary kitchen salt, indicated 
in my judgment, the greater solubility of the lime salt, but it would 
be difficult perhaps, aside from the deportment of the lime salt, to 
prove directly that the arsenic found in the tree had been derived 
from the lime arsenite for the ash of the tree contains some lime 
and there is scarcely an orchard soil which has not received both the 
lead and lime salts. It is impossible to tell which one has contributed 
more largely to the damage done, but owing to the length of time it 
has been used and the greater readiness with which it appears to go 
into solution, it would seem probable that the lime preparation has up 
to the present, contributed more largely to bringing about the 
trouble than the lead salt. 
It is, on the other hand, easier to obtain direct proof that the 
lead arsenate has been the source of some of the arsenic for lead 
is not a normal constituent of woody tissue and the presence of a 
trace of it suffices to prove that the lead arsenate has been the 
source of the arsenic. I tested only six of the samples for lead but 
as lead was found in each of them this number of tests is deemed 
sufficient. The lead was obtained in the metallic form and its 
identity established beyond doubt. 
The significance of this is not only that lead arsenate has been 
the source of the arsenic but that the ordinary kitchen salt present 
in the soil is probably an active agent in bringing it into solution, 
for the lead chlorid which would be formed by the interaction of the 
lead arsenate and salt is more readily soluble than the sulfate, the 
product of the interaction of Glauber’s salt and lead arsenate. In 
this case too, it seems beyond question that both salts, Glauber’s 
salt and ordinary kitchen salt,’ contribute to the damage done. 
The amounts of these salts in the soil and in some water used for 
