14 BULLETIN 1147, U. S. DEPARTMENT OF AGRICULTURE. 
Tims amounts of the arsenicals containing equivalent percentages of 
arsenious or arsenic oxid were taken in each case. 
In all the tests the mixtures of the arsenicals and other material 
were agitated in flasks by rotating in a water bath which was main- 
tained at a constant temperature of 35° C. All were made in trip- 
licate, but only the average figures are reported in the tables. The 
soluble arsenic (that found in the filtrates) was determined by the 
modified Gutzeit test (47) or by the Gooch-Browning method (1 ) . 
ARSENATES AND LIME-SULPHUR. 
Ruth (38) made a study of the chemical changes resulting when 
acid lead arsenate and lime-sulphur were mixed. He found (a) a 
decrease of lime and sulphur in the solution, (b) an increase of 
thiosulphate sulphur in the solution and in the residue, (c) an increase 
of sulphite in the solution, (d) formation of lead sulphid, and (e) the 
formation of a compound containing arsenic and sulphur, but in- 
soluble in the lime-sulphur solution. Robinson (35) , after agitating 
mixtures of lead arsenate and lime-sulphur for three days, allowed 
them to settle and then poured off the clear liquid. He found that 
25 per cent of the lime and more than 35 per cent of the sulphur had 
been precipitated and that 5 per cent of the arsenic had become 
soluble. Robinson and Tartar (37) tested mixtures of lime-sulphur 
and lead arsenates (4.8 grams of arsenate per 1,000 cubic centimeters 
of lime-sulphur, diluted 1 to 30). When basic lead arsenate was 
used little change occurred, but when acid lead arsenate was used an 
increase of soluble arsenic and a decrease of total soluble sulphur 
and polysulphid sulphur resulted. They concluded that the efficiency 
of the lime-sulphur had been reduced 25 per cent, and that the 
arsenic rendered soluble might injure foliage. Fields and Elliott 
(15) present data showing that less than five parts per million of 
arsenic oxid bv weight was made soluble when solutions of lime- 
sulphur were mixed with either acid or basic lead arsenates. 
In the present investigation standard commercial lime-sulphur 
solution was diluted (1 to 30) with recently boiled and cooled distilled 
water. Control flasks (500 cubic centimeters volume), completely 
filled with this diluted solution, were securely closed with stoppers 
and paraffin and agitated for 1-hour and 91-hour periods. Other 
flasks, filled with the diluted solution of lime-sulphur, to each of 
which 1.2 grams of powdered acid lead arsenate (sample 39) had been 
added, were similarly treated. Series of three flasks were removed, 
and the solutions were filtered immediately on removal from the bath. 
The results obtained with lead arsenate are given in Table 6. 
