New York AGRICULTURAL EXPERIMENT STATION. 705 
Potassium Ferrocyanide .Test. 
Pour the lime into the copper sulphate solution, stir the mix- 
ture thoroughly and then add a drop of the potassium ferro- 
cyanide. 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 color. More lime must then be 
added till the potassium ferrocyanide does not change color 
when dropped into the mixture. A little more lime should be 
added after this test shows no color, as it sometimes happens if 
the mixture has not been thoroughly stirred, that some of the 
copper sulphate in the bottom of the barrel has not yet been 
precipitated, while at the surface the mixture shows no color 
when the test is applied; so it occasionally happens that after 
the mixture has been standing a few minutes the potassium ferro- 
cyanide will again give the dark color, showing that not enough 
lime had been used. 
The potassium ferrocyanide, also known as the yellow prussi- 
ate of potash, is a poisonous substance. It isa yellow salt which 
readily dissolves in water and a solution may conveniently be 
kept on hand ina small bottle. The commercial form of the pot- 
assium ferrocyanide may be used. A few cents should purchase 
enough to last through the season. 
' Excess of Lime. 
It is important that enough lime be added, otherwise the mix- 
ture may injure the foliage, while an excess of lime will not harm 
the foliage. 
KerRosEngE EMULSION. 
Kerosene emulsion is made by dissolving one-half pound of 
common soap or whale oil soap in one gallon of soft water. Heat 
the mixture and when boiling hot remove it from near the fire 
and add it to two gallons of kerosene. The whole is now thor- 
oughly mixed by pumping continuously through a small force 
pump for about five minutes. Mix until the ingredients form a 
creamy mass that becomes thick when cool and from which the 
oil does not separate. When using on foliage dilute with from 
10 to 15 parts of water ; when used as a winter treatment it may 
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