3 SCIENCE AND INDUSTRY. 
In all cases it is advisable to use combined sprays as soon as they 
are prepared. The following combinations occur :— 
(1) Arsenate of Lead + Lime Sulphur Solution. 
(2) : » + Bordeaux. 
(3) Nicotine --+ Lime Sulphur. 
(4) ni + Bordeaux. 
(5) Arsenate of Lead ++ Nicotine. 
(6) * 3 + Nicotine + Lime Sulphur. 
(7) v 4 -+ Nicotine + Bordeaux. 
(8) Soap --+ Nicotine. 
C2) ss + Ammonium Poly-sulphide. ~ 
(GLO; oes + Am. Poly-sulphide + Nicotine. 
(11) Oils Emulsified with soap. 
(1) Arsenate of Lead + Lime Sulphur. 
In the first case on the chart, combining arsenate of lead with 
lime sulphur will lead to trouble, if it be not restricted to the 
neutral type of lead arsenate. In America, good results have been — 
obtained by mixing calcium arsenate instead of lead arsenate. 
Lime sulphur is easily decomposed, and is especially susceptible to 
change when mixed with other strays. Its own decomposition pro- 
ducts are quite harmless, but its effects on its associates are 
frequently of a serious nature. If a lead arsenate of an acid 
character is used, soluble arsenic is likely to be found in the mix- 
ture, as arsenates are prone to yield soluble arsenic, especially 
in alkaline solution, but also in acid ones. Lime sulphur is an 
alkaline solution, and therefore all mixtures of lead acetates with 
lime sulphur are to be handled with suspicion. Soluble arsenie in 
the spray would soon ruin the trees. , 
Owing to the very great value and wide application of this 
combination, however, experiments have been made to ascertain 
how to correct the rapid changes that take place when these sub- 
stances are mixed. In the United States of America it appears 
that 95 per cent. of the lead arsenate used is of the acid type, 
whereas in Australia, I believe, the neutral or tribasic lead arsenate 
finds most favour, probably because the brands that have given the 
best results happen to be of the neutral type. Mixtures of the 
neutral lead acetate and lime sulphur are fairly reliable. With 
the acid arsenate, changes of a more serious nature take place, and 
within two days of mixing all the polysulphides will be changed 
to lead sulphide, which is ineffective as an insecticide; but what 
is more objectionable, as much as 12 per cent. of soluble arsenic 
compounds may be found in solution. Such a mixture sprayed on 
trees would result in disaster. It has been found that if 10 Ibs. 
of slaked lime be added to 100 gallons of diluted lime sulphur solu- 
tion ready for spraying followed by the addition of the acid lead 
arsenate at the rate of 2 lbs. to the 100 gallons, the active poly- 
sulphides will be retained, and the arsenic will not be converted to 
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