20 BULLETIN 1147, U. S. DEPARTMENT OE 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 S0 4 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 found. 
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 (39) 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 spraved 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 thQ 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. 
