﻿ARSENICALS. 



51 



arsenate combination, six times as much arsenic is former] as in flip 

 calcium arsenate combination. Acid lead arsenate, I li<nl'or<\ -liould 

 not be used in preparing kerosene-emulsion sprays, as the mixture i- 

 chemically incompatible. Gray (16) reports that basic lead ar lenate 

 is not affected by the alkali of soap. 



When acid lead arsenate was mixed with solutions of nicotine sul- 

 phate, no chemical incompatibility was found. When calcium 

 arsenate was used with nicotine sulphate, however, the Jailer was 

 decomposed and free nicotine was formed. The SO,, of the nicotine 

 sulphate combined with free lime (CaO), if present, or with lime of the 

 calcium arsenate, and large amounts of soluble arsenic were formed 

 in certain mixtures. Free nicotine is present in all of these mix! 1 1 res . 

 The free nicotine is not dangerous but the soluble arsenic is. These 

 mixtures are chemically incompatible. The findings in connection 

 with the chemical compatibilities and incompatibilities of the various 

 arsenicals, fungicides, and other materials tested are summarized in 

 Table 23. Gray (16) in 1914 published a summary of data on the 

 compatibilities of various spray materials which he had collected. 



Table 23. — Chemical compatibility of arsenicals combined with other spray materials. 





Other spray materials used. 



Arsenicals used. 



Lime sulphur. 



Bordeaux 

 mixture. 



Kerosene 

 emulsion. 



Sodium flsh- 

 oi] soap. 



Nicotine-sul- 

 phate solution. 



Acid lead arsenate 



Incompatible... 



Compatible . Incompatible. . . 



Incompatible... 



Compatible. 

 Incompatible. 







do 









do 

















Sanders and Brittain (41) tested the comparative insecticidal prop- 

 erties of the arsenates of calcium, barium, and lead, alone and in com- 

 bination with Bordeaux mixture, lime-sulphur, barium tetrasulphid, 

 and sodium sulphid (" soluble sulphur"), on one species of insects. 

 The results obtained showed that the presence of a fungicide had a 

 marked influence on the efficiency of the arsenical investigated. The 

 four arsenicals were 13 per cent more efficient when used with sodium 

 sulphid than when used alone. The toxicity of the arsenicals was 

 reduced when they were mixed with any of the other fungicides. The 

 explanation given by these authors for the increased toxicity resulting 

 from the use of sodium sulphid with an arsenical is that the sodium 

 increases the palatability of the sprayed leaves, which causes the 

 insects to eat ravenously for a few days. The insects thus take a large 

 amount of arsenic into their systems in a short time and death rapidly 

 ensues. 



Mixing sodium sulphid with acid lead arsenate produces some lead 

 sulphid and sodium arsenate. The sodium arsenate is soluble and 

 therefore may be more active than the original acid lead arsenate. 

 The results in Table 21 indicate that the soluble arsenicals are more 

 toxic per unit of arsenic than are the insoluble ones, the greater 

 toxicity being due to the water-soluble arsenic present in the com- 

 pound or to the arsenic which is quickly rendered soluble inside the 

 insects. Data obtained during this investigation suggest that the 

 amount of arsenic present per unit of sprayed leaf is larger when a 



