INSECTICIDES AXD FUNGICIDES 189 



bottom of the barrel. Now slake carefull}^ five pounds of good 

 quicklime, using just enough water to slake it slowly. Be sure 

 that the lime is not at all air-slaked. AVhen the lime is slaked, 

 add enough 'water to make twenty-five gallons. Now stir it care- 

 fully and then pour together the copper sulphate solution and 

 the milk of lime. It is desirable to have a slight excess of lime, 

 since it prevents any injurious action of the co]iper salts. If 

 there is an excess of copper, foliage injury is liable to result. 

 Therefore, two simple tests should be made to determine whether 

 or not the mixture is safe to use. Take a piece of newly-filed 

 iron or steel and put it into the mixture for about a minute. If 

 it has a copper coating when it is taken out, there is an excess of 

 copper, and more lime should be added. To determine whether 

 or not there is a sufficient amount of lime in the mixture, pour 

 some of it into a flat dish and blow on it for a few moments. If 

 a film forms on the surface, enough lime is present; if not, more 

 should be added. 



In making stock solutions, dissolve copper sulphate in water 

 at the rate of one pound to one gallon of water. Slake the lime 

 slow^ly in another receptacle, and, Avhen slaked, add water until 

 a thick lime milk, one pound to one gallon of water, is formed. 

 When using the stock solution in making up the spray mixture, 

 one gallon of copper sulphate solution represents one pound of 

 copper sulphate, and one gallon of lime water represents a like 

 amount — more or less, depending on the quantity of water used 

 in making the stock solution. The proper amount of stock solu- 

 tions should be diluted separately before they are poured 

 together. The stock solution of lime should be first run through 

 a fine-mesh sieve, to remove all lumps which might clog the 

 nozzle of the sprayer. 



Carbon bisulphid. — This is a very inflammable liquid, that 

 volatizes readily when exposed to the air. It is one of the gase- 

 ous insecticides used against grain weevils, etc. 



Copper sulphate wash. — 



Formula : 



Copper sulphate, 3 pounds. 

 Water, 50 gallons. 



This is used as a wash on dormant trees, for the prevention of 

 such diseases as apple scab. It must never be used on trees after 

 the buds have burst. 



Corrosive sublimate. — 



FORMTTLA : 



^Mercury bichloride (corrosive sublimate), 2 ounces. 

 Water, 15 gallons. 



