﻿ARSENICALS. 



15 



Table 6. — Composition of lime-sulphur solution and of the filtrates from wixtures of 

 lead arsenate or calcium arsenate and lime-sulphur solution. 





After 

 having 



been 

 shaken 



for— 



Composition (grams per 500 cubic centime 1 1 i 



Material analyzed. 



Total 

 lime 

 (CaO). 



Total 



sulphur 



(§). 



Sulphid 



sulphur 



(S). 



Thio- 



sulphattf 



sulphur 



(§). 



Sulphate 



sulphur 



(§). 



' 



Series 1: 



Lime-sulphur solution 



Filtrates from mixtures of 



fl hour 

 \91 hours... 

 fl hour 

 1 19 hours... 



1. 9680 

 2. 0520 

 1. 8050 



4. 9430 

 4. 9290 

 4. 4770 

 4.2670 

 4.2560 

 4.2790 



5.2500 

 5. 2500 

 5.2000 

 5. 1000 

 5. 0500 

 5. 1000 



4. 5190 

 4.5060 

 4. 1620 

 4. 0450 

 3. 9080 

 3.7110 



4.7800 

 4. 7500 

 4. 7000 

 4.7500 

 4. 6800 

 4. 7000 



0. 1960 

 .2030 

 . 2020 

 .1990 

 .1980 

 .1970 



.3200 

 . 3200 

 .3300 

 .3200 

 .3300 

 .3600 



0. 0035 

 .0069 



.002!) 



. 0055 

 .0036 



.0076 



.0089 



.009') 

 . 0077 

 .OO.S'.I 

 .0087 

 .0108 



0.0002 

 . 0002 

 . 0270 



. 0205 



lead arsenate and lime- 

 sulphur solution 



Series 2: 



Lime-sulphur solution 



Filtrates from mixtures of 

 calcium arsenate and 

 lime-sulphur solution . . . 



1 43 hours... 





.0199 



(91 hours... 



fl hour 

 -J21 hours... 



(5 days 



fl hour 



J.21 hours... 

 |5 days 



1. 8030 



1.9800 

 1.9900 

 2. 0400 

 2.0400 

 2. 0600 

 1.9600 



. 0200 



.0002 

 .0002 



.0003 

 .0008 

 .0005 

 .0010 



Usinoj the analytical data on the lime-sulphur solution as controls, 

 the analytical results on filtrates from a mixture of lead arsenate and 

 lime-sulphur solution show the following: (a) The total lime in 

 solution was reduced 10 percent after having been shaken for either 

 1 hour or 91 hours; (b) the total sulphur in solution was reduced 9.5 

 per cent after 1 hour and 14 per cent after 19, after 43, and after 91 

 hours; (c) the sulphid sulphur was reduced 8 per cent after 1 hour and 

 18 per cent after 91 hours; (d) the thiosulphate sulphur remained 

 unchanged after each period; (e) the sulphate sulphur increased 

 slightly, although the same increase was observed in the control; and 

 (/) 5.2 per cent of the total arsenic oxid of the lead arsenate used was 

 rendered soluble. From these results, it is apparent that chemical 

 changes have occurred. The mixture is therefore chemically in- 

 compatible. 5 Some of the sulphur in lime-sulphur solution probably 

 united with the lead of the lead arsenate and produced lead sulphid, 

 which could be seen as black particles in the mixture. The arsenic 

 oxid group, liberated by the decomposition of the lead arsenate, was 

 then free to combine with the lime in the lime-sulphur solution, 

 probably forming calcium sulph-arsenate. The formation of in- 

 soluble tricalcium arsenate took place only to a limited degree. 



Robinson (34) in examining mixtures of calcium arsenates and 

 lime-sulphur found that no reaction took place in such mixtures. 

 His tests with "dry lime-sulphur" mixed with calcium arsenate 

 showed the presence of no soluble arsenic, but those with "soluble 

 sulphur" mixed with calcium arsenate showed that it was present. 

 Lovett (24) also reported that no changes take place when calcium 

 arsenate is mixed with lime-sulphur solution. 



Experiments similar to the lead arsenate tests were performed, 

 using calcium arsenate (sample 57) in place of the acid lead arsenate. 

 A series of 500 cubic centimeter flasks were filled with lime-sulphur 

 solution diluted 1 to 30. Nine of the flasks were used as controls; 

 to each of the others 1 gram of calcium arsenate was added. The 

 solutions were agitated for periods of 1 hour, 21 hours, and 5 days. 

 They were immediately filtered and the filtrates were tested. 



s The term "compatible" is here used only in the chemical sense. 



