COMMERCIAL CALCIUM ARSENATE. 9 
much water, by weight, as lime, and have it, preferably, warm. Let 
it stand for a while and then thoroughly mix, after which add twice 
as much hot water as was used for slaking, and mix again. 
3. The lime and arsenic should be in such proportion that the 
weight of actual calcium oxid used will equal that of the arsenic oxid 
used. This gives a product with a molecular ratio slightly over 4 to 1, 
which is necessary if the soluble arsenic oxid is to be kept down to 
desirable limits. 
4. Add the acid at room temperature to the lime as quickly as 
possible and stir well until the liquid becomes alkaline to phenol- 
phthalein. 
5. Filter to as dry a state as possible. Do not wash. If a dry 
product is desired, dry directly in any suitable manner. 
6. Crush in a suitable disintegrator, or grind if necessary. 
The production of 100 pounds of a co mm ercial grade of calcium 
arsenate by this process will require 45 pounds of calcium oxid 
(approximately 50 pounds of a high-grade lime) slaked with 18 
gallons of water, the addition of 36 gallons of water, and then of 
45 gallons of a solution containing 1 pound of arsenic oxid per gallon. 
A slight departure from the quantities given for water will probably 
have little effect. 
LABELING THE PRODUCT. 
A product prepared in accordance with the procedure outlined 
is, of course, not pure calcium arsenate, but consists of tricalcium 
arsenate, probably with some water of crystallization, together with 
excess of other calcium compounds, such as calcium hydroxid and 
calcium carbonate. The product, therefore, should not be designated 
simply " Calcium Arsenate," but by some such term as, " Calcium 
Arsenate Containing other Calcium Compounds." In labeling such 
a product, the following is suggested by the Insecticide and Fungicide 
Board of this department as the simplest form of statement which 
will fulfill the requirements of section 8 of the insecticide act of 1910, 
relating to the statement of active and inert ingredients and total 
and water-soluble arsenic. 
Active ingredient: 
Tricalcium arsenate % 
Inert ingredients % 
Total arsenic (as metallic) % 
Arsenic in water-soluble forms (as metallic) % 
