254 FUNGICIDES AND GERMICIDES FOR PLANT DISEASES 



stone) are mixed. Many formulas have been recommended and 

 used. The 5-5-50 formula may be regarded as standard. In such 

 a formula the first figure refers to the number of pounds of copper 

 sulfate, the second to the stone or hydrated lime, and the third 

 to the number of gallons of water. Bordeaux must often be used 

 as weak as 2-2-50, on account of injury to some plants. 



To make 50 gallons of bordeaux mixture, proceed as follows: (1) 

 Pulverize 5 pounds of copper sulfate (blue vitriol), place in a glass, 

 wooden, or brass vessel, and add two or three gallons of hot water. 

 In another vessel slake 5 pounds of quicklime in a small amount 

 of water. When the copper sulfate is all dissolved, pour into a 

 barrel and add water to make 40 or 45 gallons. Now strain the 

 lime into this, using a sieve 50 meshes to the inch or a piece of 

 cheese-cloth supported by ordinary screening. Stir thoroughly, 

 and add water to the 50-gallon mark. The flocculent substance 

 which settles is the effective fungicide. Always stir vigorously before 

 filling the sprayer. Never add the strong lime to strong vitriol. 

 Always add a large amount of water to one or the other first. 

 Blue vitriol used alone would not only wash off quickly in a rain, 

 but cause a severe burning of fruit and foliage. Lime is added to 

 neutralize this burning effect of the copper. If the lime were 

 absolutely pure only slightly more than one pound would be re- 

 quired to neutralize this burning effect. For many purposes an 

 excess of lime is not objectionable and may be desirable. For 

 nearly ripe fruit and ornamentals an excess of lime augments 

 spotting. In such cases the least amount of lime possible should 

 be used. Determine this by applying the cyanide test (2). 



(2) Secure from the druggist 10 cents' worth of potassium 

 ferrocyanide (yellow prussiate of potash) and dissolve it in water 

 in an 8-ounce bottle. Cut a V-shaped slit in one side of the 

 cork, so that a few drops of the liquid can be obtained. Now 

 proceed as before. Add lime with constant stirring until a drop 

 of the ferrocyanide ceases to give a reddish-brown color. 



(3) When bordeaux mixture is desired in large quantities, stock 

 solutions should be made. Place 100 pounds of copper sulfate in 

 a bag of coffee-sacking, and suspend in the top of a 50-gallon 



. barrel, and add water to the 50-gallon mark. In twelve to fifteen 

 hours the vitriol will be dissolved and each gallon of solution will 



