CALCIUM ARSENATE. 5 
along this line. Each series included 8 experiments, the molecular 
ratio, CaQ/As 2 0- being varied from 3 to 5 by appropriate steps. The 
amount of As 2 G 5 used was kept constant, being 25 cubic centimeters 
of a solution containing 0.4 gram As 2 5 per cubic centimeter (in 
other words, a total of 10 grams As 2 5 ). The weighed amounts of 
lime were slaked in beakers with 3 times their weight of boiling 
water, and the cold arsenic solution added rather slowly, from a 
pipette, Avith constant stirring. In one series (A) the acid was 
added to the lime while still hot from slaking; in the other series 
(B) the lime paste was permitted to cool to room temperature be- 
fore mixing. Each mixture was then divided into two portions, one 
of which was permitted to stand over night, then decanted, the other 
being filtered and sucked as dry as possible on a Buchner funnel for 
the purpose of determining the amount of water each process left 
in the paste. Water was determined in portions of each paste by 
drying in the oven at 105 °C. The dried portions were used for 
chemical analysis. The water-soluble arsenic was determined on 
the dry material, using 1.2 grams in 500 cubic centimeters (equiva- 
lent to 1 pound in 50 gallons). The results of these experiments 
are summarized in Table 1. 
