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



When calcium arsenates are combined with nicotine sulphate 

 solutions, soluble arsenic oxid may be produced, depending on the 

 sample of calcium arsenate used and on the quantity of nicotine 

 sulphate present in the mixture. The percentage of soluble arsenic 

 oxid will be low if there is enough excess lime in the calcium arsenate 

 to combine with the S0 4 of the nicotine sulphate. If sufficient excess 

 lime is not present, the SO, combines with some of the CaO of the 

 calcium arsenate, liberating soluble arsenic oxid. Calcium arsenate 

 (sample 57) contained 13.16 per cent of free calcium oxid, and when 

 combined with nicotine sulphate only 0.5 per cent of free arsenic 

 oxid was found. Calcium arsenate (sample 32) contained 9.99 per 

 cent of free calcium oxid, and when combined with nicotine sulphate 

 1.15 per cent of soluble arsenic oxid was foimd. 



When the free lime in the calcium arsenates was low or absent 

 entirely there was a marked rise in the percentage of soluble arsenic 

 oxid. For example, sample 59, containing 5.23 per cent of free cal- 

 cium oxid, and sample 464, containing no free calcium oxid, gave 

 practically 12 per cent of soluble arsenic oxid. Sample 6 (3.68 per 

 cent free calcium oxid) and sample 58 (9.06 per cent free calcium 

 oxid) gave, respectively, 6.67 and 2.28 per cent of soluble arsenic 

 oxid after being agitated for 1 hour with nicotine sulphate solution 

 in the proportions given. These mixtures, therefore, are chemically 

 incompatible, and the only way that such a combination should be 

 made is to use a high-grade calcium arsenate containing at least 10 

 per cent of excess calcium oxid and using a proportion of nicotine 

 sulphate no higher than that used in these tests. 



The lime of calcium arsenate decomposes the nicotine sulphate, 

 leaving free nicotine, but does not change the amount of nicotine 

 present. The results given in Table 9 show that the percentage of 

 soluble nicotine was not altered by the presence of calcium arsenates. 



A few tests made in the insecticide and fungicide laboratory in 

 which free nicotine, solution was mixed with acid lead arsenate or 

 with calcium arsenate showed that these combinations were chemi- 

 cally compatible. Results obtained on combining nicotine sulphate 

 solutions with Bordeaux mixture were reported by Safro (89) and 

 Wilson {52), who claimed that such mixtures were compatible. 



PHYSICAL PROPERTIES OF ARSENICALS. 



A commercial calcium arsenate and a commercial acid lead arsenate 

 were selected for a series of tests on the adhesive properties of these 

 substances on sprayed foliage, which was extended over three seasons 

 (1917, 1918, and 1919). For each 50 gallons of water 1 pound of 

 powdered acid lead arsenate or an equivalent amount of calcium 

 arsenate, based on the arsenic oxid content, was used. The sprays 

 were applied to potato and apple leaves with a power sprayer. At 

 various periods after the sprays had been applied leaves were gath- 

 ered for analysis. The leaves were dried and samples of approxi- 

 mately 5 grams each were digested with nitric and sulphuric acids 

 and analyzed for arsenic by the modified Gutzeit (47) method. The 

 results (Table 10) by this method do not warrant in all cases the ex- 

 pression to the degree of accuracy which the figures may imply, but 

 this is the common way of expressing results where small amounts of 

 a substance are present. 



