520 
Journal of Agricultural Research 
Vol. XXIV. No. 6 
compounds, and indeed it was scarcely more injurious than the crystalline 
form. 
On the other hand, it seems surprising that calcium arsmite could have 
remained in use as an insecticide for so long as it did. It has gradually 
been abandoned, partly because of its burning of the-foliage and partly 
because some time is consumed in its preparation according to the Kedzie 
(Woodworth and Colby (J7)) or the Kilgore {14) formulas, which are the 
ones most generally followed. We have tried three different brands, one 
of them especially prepared for our use, besides the home-made articles 
prepared after the Kedzie and the Kilgore formulas, and are left no other 
alternative than to place it at the head of the list of slightly soluble arsen¬ 
ical compounds, considered from the standpoint of injurious properties. 
Indeed, used in strengths to contain equal amounts of arsenic, the home¬ 
made calcium arsenites were even more harmful than the Baker brand 
on which we based most of our work. 
To determine the variability of compounds supposed to be identical, 
tests were made with different brands of calcium arsenite, lead arsenate, 
zinc arsenite, and arsenic trioxid, using four brands of calcium arsenite, 
4.9 gm. to 2 liters of water, and applying to apple foliage. Of the 
four, one^ caused in a typical case moderate injury; the second,^ very 
slight; the third,® bad; and the fourth,^ very slight. In this case there 
was no consistent relation between the arsenic content of the different 
brands and the amount of injury produced. 
More than 30 brands of lead arsenate were tried. Some were supposed 
to be diplumbic, others triplumbic, and others mixtures of the two, while 
still others gave no clue without chemical analysis as to their kind. 
Some were paste and others were dry. Some were prepared for use as 
insecticides and others as pine chemicals for technical use. It is doubtful 
if the results of these tests merit publication in tabular form. Marked 
differences were found, to be sure, but as some factories do not put out a 
uniform product, and as others have changed their processes of manu¬ 
facture since the tests were made, and still others will doubtless do so in 
the near future, such a list could not safely be used as a basis for selecting 
lead arsenates for orchard spraying. The same could, perhaps, be said 
also of the calcium arsenites and zinc arsenites discussed above. The 
important point is that lead arsenates do vary in composition, as indicated 
by their analyses and by their injurious properties, even though the labels 
would not indicate the fact. 
It is generally believed that diplumbic lead arsenate has a greater 
tendency to injme foliage than the triplumbic form. This is doubtless 
true in a general way, but we have had some brands of the diplumbic that 
were just as safe to use as most of the brands of triplumbic arsenate. 
Four lots of arsenic trioxid were compared, a crystalline form and an 
amorphous form from one manufacturer,® a crystalline form from an¬ 
other,® and a crystalline form taken direct from the arsenic retainer of 
a smelter^® situated at Anaconda, Mont. In addition, an arsenic trioxid 
paste was made from each of these four by grinding the dry powder in a 
mortar with a little water. This was allowed to stand a week or more 
before using. The injury caused by these various lots of arsenic trioxid 
was practically equal. 
* Adler's. 
® California Spray Co.'s “Ortho 40.” 
• Sherwin-William’s. 
^ Thomson’s. 
• J. T. Baker. 
» Merck. 
1® The Washoe. 
