14 
SPICES 
CHAP. 
follows : It is in the form of a wooden box about 1 ft. square, 
the bottom of which is formed of hard wood, with a hole bored 
through it, into which a piece of gaspipe, in. or 2 in. in 
diameter and from 6 in. to 9 in. long, is fitted. 
The box is, of course, open at the top. Fitting just inside 
this box is a second and lighter box, also open at the top, and 
having an overhanging strip nailed round the top which supports 
it. The bottom of this inner box should be made so as to slope 
at an angle of about 30°, and should be made of fine copper 
gauze. The slanting bottom makes it harder to clog, and the 
inner box, being removable, can be inverted and washed in a 
tub of water. Bordeaux mixture, if properly strained, will pass 
easily through nozzles which throw the finest “ misty ” spray, 
while if not properly strained, frequent clogging of the nozzle 
will result. 
If the lime used is freshly burnt (and it must never be for- 
gotten that air-slaked lime is useless for making Bordeaux 
mixture) and carefully weighed out, there is no need to test the 
mixture before using it. When using “ stock solutions,” it is a 
good plan to apply a test at the first mixing. A rough test 
consists in immersing a clean iron wire or French nail in the 
Bordeaux mixture for one minute ; if safe to use, the mixture 
does not affect the nail ; while if unsafe, a copper-plated appear- 
ance is given to it. A more delicate and quite simple test is 
as follows : procure from a chemist a 10 per cent solution of 
ferrocyanide of potassium (which is a poison) and pour a little 
of this into a white saucer; then drop a few drops of the 
Bordeaux mixture into the ferrocyanide of potassium. 'No 
change of colour occurs if the mixture is safe to use, while a 
cloudy reddish-brown discoloration (very easy to see) occurs 
immediately if the mixture is unsafe to use. An unsafe mixture 
can be made safe by adding more “ milk-of-lime ” until it passes 
the test. 
In spraying there is no need whatever to add anything to 
the Bordeaux mixture with the object of making it adhere 
better; soap is quite unnecessary and should never be used, 
and treacle is useless. The nature of the precipitate which 
constitutes Bordeaux mixture causes it, when applied in a 
“misty” spray (see below), to adhere most intimately to the 
part sprayed. 
The Ap'plication of Bordeaux Mixture . — The best type of 
spraying machine for spraying with Bordeaux mixture depends 
to a large extent on such circumstances as the height of the 
trees, and whether they are grown in a plantation or in an 
orchard. But the chief point that requires to be emphasised 
