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makes it harder to clog, and the inner box, being removable, can be 
inverted and washed in a tub of water. Bordeaux mixture, if proper- 
ly strained, will pass easily through nozzles which throw the finest 
“ misty ” spray, while if not properly strained, frequent clogging of 
the nozzle will result. Where all the fluid has to pass through the 
minute hole in the circular disc— and owing to the Bordeaux mixture 
used having been properly strained, have not had to stop once for 
any blocking of the nozzle. 
If the lime used is freshly burnt (and it must never be forgotten 
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 of 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 appearance 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. JMo 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 fruit trees (and also potatoes) 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 
« m isty ” spray (see below), to adhere most intimately to the part 
sprayed. 
Ready-made Bordeaux mixture is at present put on the market 
in powder form, and as a paste. The best results, however, in my 
experience, are only obtained when Bordeaux mixture is home-made 
and freshly-mixed. As regards the numerous proprietary Bordeaux 
mixtures put up in powder form, the fruit-grower must be warned 
against using these. Such preparations are made by mixing lime 
and copper sulphate in concentrated form, and then drying and 
grinding the product. As Mr. S. U. Pickering has lately pointed 
out,t Bordeaux mixture made from these proprietary powders settles 
at least ten times more rapidly than the freshly-prepared mixture ; 
consequently it is a very inefficient spraying material. There is a 
general consensus of opinion that in practical spraying dried 
Bordeaux mixture is less efficient than the ordinary mixture. As 
long ago as IQOO, Mr. R. U. Moss pointed out | how thoroughly 
See Pickering, in Jour. Auric. Science, iii ( 1909 ). 
t Jour. Agric. Science, iii. I/O (I9°9)- 
i Eton. Proc. Royal Dublin Soc., vol. i, part iii, p. 109- 
