706 Report oF THE HORTICULTURIST OF THE 
color. More lime must then be added till the potassium ferro- 
cyanide does not change color when dropped into the mixture. 
The potassium ferrocyanide, also known as the yellow prussi- 
ate of potash, is a poisonous substance. It is a yellow salt which 
readily dissolves in water and a solution may conveniently be 
kept on hand in a small bottle. The commercial form of the 
potassium ferrocyanide may be used. A few cents should pur-, 
chase enough to last through the season. 
Excess of lime.— It is important that enongh lime be added, 
otherwise the mixture may injure the foliage, while an excess of 
lime will not harm the foliage. fs 
Use fresh Bordeaux mixture.— We prefer to use the fresh 
Bordeaux mixture because it becomes granulated after standing 
awhile and it seems to stick better to the foliage if applied fresh. 
Fresh slacked lime _It is best to use either fresh slaked lime, 
or lime kept in the condition described below, because it takes 
less of this to form the Bordeaux mixture than it does of air slaked 
lime, and because the mixture made with the fresh slaked lime 
sticks to the foliage better than that made with the air slaked 
lime. The lime may be slaked in large quantities if it is kept 
covered with water to exclude the air after the manner com- 
monly practiced by masons. In this way the lime will keep io 
an indefinite period in satisfactory condition. 
Stock solution of copper sulphate— Some have made a 
practice of dissolving the copper sulphate in large quantities 
making a strong solution from which small portions are meas- 
ured out as needed and diluted to the proper proportions required 
by the Bordeaux mixture formula. At first we were inclined to 
doubt the reliability of this method from the fact that some 
experience with saturated solutions indicated that portions taken 
from the bottom of a barrel of a stock solution would be stronger 
than equal portions taken from the top of the barrel. One 
gentleman who has followed this method for two years reports 
that the copper sulphate crystallized out of the solution forming 
erystals on the bottom and sides of the barrel in which the stock 
solution was kept. This shows that he has not been making the 
Bordeaux mixtures.of uniform strength. The portion of the 
stock solution used after the crystals began to form must have 
been a saturated solution, and must have made a stronger Bor- 
deaux mixture than that used before the crystals began to form. 
