APPENDIX I 673 



Testing Bordeaux Mixture. — When Bordeaux mixture is properly prepared it is of 

 a brilliant sky-blue color. If the lime is air-slaked, or otherwise inferior in quality, 

 resulting in a bad mixture, the preparation will have a greenish cast, and if this is 

 very pronounced the mixture will injure the foliage. In order to make certain that 

 the copper sulphate is properly neutralized by the lime, the yeUow prussiate of potash 

 test may be used. A small bottle containing a 10 per cent, solution of yellow 

 prussiate of potash can be secured from a druggist. After stirring the Bordeaux 

 mixture a drop of this solution is allowed to fall on the surface of the preparation. 

 If free copper is present, the drop will turn reddish brown in color immediately. 

 Lime should then be added until the brown color fails to appear. If the reaction 

 is complete, the yellow prussiate of potash solution will remain a clear yellow until 

 it disappears in the mixture. 



Bordeaux Mixture and Insecticides. — One advantage of Bordeaux mixture is the 

 possibility of adding arsenical insecticides to the preparation and thus of spraying 

 at the same time for fungous diseases and for the codling-moth and leaf-eating in- 

 sects. Paris green at the rate of J4 pound to 50 gallons of Bordeaux mixture, may 

 be considered as the standard formula for this purpose. London purple, arsenate of 

 lead and other arsenicals may be used in the same way. Bordeaux mixture may be 

 considered as so much water in the formulas for this class of insecticides. As a 

 matter of fact, the slight excess of lime in the standard mixture renders it an espe- 

 cially suitable medium for distributing these insecticides. 



Dust Bordeaux Mixture. — This mixture is prepared as follows: 



4 pounds of copper sulphate in 4 gallons of water. 

 4 pounds of lime in 4 gallons of water. 

 5o pounds of slaked lime dust. 



Dissolve the 4 pounds of copper sulphate in 4 gallons of water and slake 4 pounds 

 of lime in 4 gallons of water, when cold pour the two solutions together simultaneously 

 into a tub. Allow the resulting precipitant to settle, decant off the liquid, pour 

 the wet mass of material into a double flour bag, and squeeze out as much water as 

 possible. Then spread the dough-like mass in the sun to dry. After a day's dry- 

 ing it can be crumbled easily into an impalpable powder by crushing with a block 

 of wood. This powder should be screened through a brass wire sieve having at least 

 8 J meshes to the inch and should be inixed thoroughly with 60 pounds of slaked lime 

 dust. The lime dust is best prepared by slowly sprinkling a small quantity of water 

 over a heap of quick lime, using barely enough water to cause the lime to crumble 

 into a dust. The heat generated will soon drive off the excess of moisture, and the 

 dust should be passed through a screen of 80 meshes to the inch. This powder is 

 applied bj' means of a blower. If desired 4 pounds of sulphate and i pound of Paris 

 green may be added to each 60 pounds of Bordeaux mixture dust. For details, 

 consult Waite M. B.: Fungicides. U. S. Farmers' Bull. No. 243 (1906). 



Copper Sulphate Wash. 



Copper sulphate, 3 pounds. 

 Water, 50 gallons. 



43 



