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Wisconsin State Horticultural Society / Annual report of the Wisconsin State Horticultural Society for the year 1910
Volume XL, Part II (1910)

Richards, M. W.
How to make Bordeaux mixture,   pp. 150-153 PDF (937.1 KB)


Page 153


WINTER MEETING.
153
solution will be lumpy. In using these stock solutions for the
4-4-50 formula 4 gals. of each are taken and diluted to about
10 or 15 gal. This dilution is done because it has been found
that the materials when mixed in a concentrated form make a
poor mixture and the resulting Bordeaux does not remain in sus-
pension well. The diluted Copper Sulphate and lime are then
poured into a third vessel through a gunny bag sieve and the
result is Bordeaux.
Another way of making up stock solutions is by using a satur-
ated solution of copper sulphate. This solution is obtained by
using enough of the sulphate in the gunny bag which is sus-
pended in the stock barrel so that the solution will become sat-
urated. It has been found that 1 gal. of a saturated solution oj
at the average temperature contains 3 lbs. of sulphate. The
lime stock solution is made up by slaking no definite amount of
lime and making up to no definite amount in the stock barrel.
The mixture is made by taking 1 1-3 gal. of the sulphate solu-
tion diluting it and mixing it with an amount of diluted stock
lime. The resulting mixture is then tested with potassium
ferro-cyanide or as it is commonly called yellow prussiate of
potash. When a few drops of the potassium ferro-cyanide is
dropped on the mixture if an excess of copper is present a dark
brown precipitate will be formed. More lime should be added
if this brown precipitate results. When enough lime has been
added to neutralize the effects of the copper no brown precipi-
tate will result upon adding potassium ferro-cyanide. The ad-
vantages of this method of procedure are that it is less trouble to
make the stock solutions and that they will keep indefinitely with
no danger of their changing strength.
In conclusion I will mention a few precautions to be exer-
cised in the preparation of Bordeaux Mixture.
1st. Use good materials.
2nd. Do not use air-slaked lime.
3rd. Do not mix in a concentrated form.
4th. Do not use metal utensils.
5th. Always test mixture for free copper.
6th. Always make according to some well established formula.
If these precautions are observed satisfactory Bordeaux is sure
to be obtained.


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