CALCIUM ARSENATE. 



along this line. Each series included 8 experiments, the molecular 

 ratio, CaO/As 2 Og being varied from 3 to 5 by appropriate steps. The 

 amount of As 2 O g used was kept constant, being 25 cubic centimeters 

 of a solution containing 0.4 gram As 2 3 per cubic centimeter (in 

 other words, a total of 10 grams As 2 5 ). The weighed amounts of 

 lime Mere slaked in beakers with 3 times their weight of boiling 

 water, and the cold arsenic solution added rather slowly, from a 

 pipette, with constant stirring. In one series (A) the acid was 

 added to the lime while still hot from slaking ; in the other series 

 i'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 Biichner 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 

 <Iiying 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. 



