Arsenical Poisoning of Fruit Trees. 29 
they actually do. The alkalis in our soils certainly tend to increase this 
solubility, but as stated, we find so much water soluble arsenic in soils 
free from alkali that I am now very much inclined to attribute a rather 
small part to them, and to take the statement first made by Prof. Whip¬ 
ple, that “soil conditions seem to have no relation to the disease” in the 
broadest possible sense. I, however, am not willing to say that the 
alkalis have no influence but simply that I am convinced that they have 
much less influence on the question than I formerly thought. This 
view is not only forced upon me by the fact that soils free from 
alkali contain water soluble arsenic, but also by the fact that I have 
found so many trees injured by arsenic and yet the soil in which they 
had grown could not be called an alkali soil without actual disregard of 
facts. 
In order to test this point further and at the same time to de¬ 
termine the difference in the deportment of the orthoarsenate of lead, 
Pbs(As 04) 2 and the acid arsenate, Pb H AsCX with dilute solutions of 
the ordinary “alkali” salts, i. e., sodic sulfate and chlorid, six series of 
experiments were made which extend those described in Bulletin 131 
in that sodic carbonate is included in the solutions and further we 
have endeavored to determine the arsenic acid that went into solu¬ 
tion. 
The first solvent considered is sodic sulfate, because this is 
our common alkali. Three strengthes were used: one, two and three 
grams per litre. The strongest of these is weaker than many of our soil 
waters, but is probably as strong as the soil waters in the majority 
of our orchards. It is very certain that quite a number of orchards 
can be found in which the soil itself will contain a larger amount of 
sodic sulfate than 0.1 per cent, or one part per thousand; on the other 
hand there are a great many that do not contain this much. This 
statement is made because there are many places where we sometimes 
meet with saturated solutions of this salt and this condition is sup¬ 
posed to apply to all, or to a very large portion, of the orchard land 
which is too broad an inference. One and one-quarter gram of the 
lead arsenate was added for each litre of the solution and the whole 
shaken frequently. 
The solubility of the acid lead arsenate in water was not de¬ 
termined but it has been previously stated that distilled water dissolves 
about 0.3 per cent, arsenic acid out of the triplumbic or neutral arse¬ 
nate. According to this each litre of water would dissolve 3.7 milli¬ 
grams of arsenic out of the 1.25 grams of ordinary arsenate of 
lead. Portions of the solution w r ere taken at the end of 24 and 72 
hours. We had some trouble to obtain perfectly clear solutions. 
The difference in the amounts of arsenic dissolved being quite small 
the range being from 3.9 to 7.2 milligrams per litre. I give the aver¬ 
age of eight determinations made with the sodic sulfate which is 5.6 
milligrams of arsenic acid per litre for the triplumbic arsenate. 
This includes the thre strengths used, j y 2, and 3 grams per litre, or 
parts per thousand. The acid arsenate, PbH AsCh, gave higher 
results from 3.8 milligrams per litre in 24 hours for the solution 
