New York AGRICULTURAL ExpEeRIMENT STATION. 705 
Probably in very rainy seasons more frequent spraying with some- 
what stronger mixture will be found profitable, while on the 
other hand, during long continued fair weather, a weaker mixture 
and less frequent sprayings would give practically as good results 
as a strong mixture frequently applied. It is doubtful whether 
the strength of this mixture may in any season be profitably 
‘reduced below that used in these experiments, namely, one pound 
of copper sulphate to about eleven gallons of the mixture. 
Strength of Bordeaux mixture.— The Bordeaux mixture used — 
at this station in the pear scab experiments of 1893 was made by 
dissolving four pounds of pulverized copper sulphate in from half 
to two-thirds of a barrel of cold water. The‘necessary amount 
of fresh slaked lime was then poured into the barrel in the form 
of athin whitewash and the whole mixture diluted to forty- 
five gallons. The copper sulphate will dissolve more readily 
if itis suspended near the upper surface of the water. A basket 
or coarse sack may conveniently be used for this purpose. 
If the solution is wanted at once hot water may be used to dis- 
solve the copper sulphate since it dissolves more quickly in hot 
water than in cold. It should never be dissolved in iron vessels. 
When the lime is poured into the solution care should be taken 
to keep out any coarse sediment that might clog the nozzle. 
Weighing and straining the lime.— It was formerly thought 
necessary to strain the milk of lime into the copper sulphate 
solution and a coarse sieve or a gunny sack was commonly used 
for this purpose. It will be found, however, that the operation of - 
straining is unnecessary if care is used in pouring. The clear 
lime water is not sufficient but the lime mixed with the water 
must be used. 
The amount of lime necessary to form the Bordeaux mixture 
was formerly determined by weighing, using two-thirds as much 
lime as copper sulphate but by means of the potassium ferro- 
cyanide test the necessity of weighing the lime is now obviated. 
Potassium ferrocyanide test.— Pour the lime into the copper 
‘sulphate solution, stir the mixture thoroughly and then add a 
drop of the potassium ferrocyanide. If enough lime has been 
added. the drop will not change color when it strikes the mixture, 
otherwise it will immediately change to a dark reddish brown 
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