﻿14 BULLETIN 1147, U. S. DEPARTMENT OF AGRICULTURE. 



Thus amounts of the arsenicals containing equivalent percentages of 

 arsenious or arsenic oxid w&re 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 (y?) 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 

 (lo) present data showing that less than five parts per million of 

 arsenic oxid by 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 *i'senate are given in Table 6. 



