372 The Principles of Fruit-growing. 



called for by the formula. The sulfate of copper may 

 be put into solution and kept in this condition in- 

 definitely, ready for use. A simple method is to 

 dissolve forty or fifty pounds of sulfate in as many 

 gallons of water, pulverizing the material and hang- 

 ing it in a coffee -sack in the top of the barrel. 

 A gallon of water, therefore, means a pound of 

 sulfate. The lime may also be slaked and kept in 

 readiness for use. Slake it into the creamy condi- 

 tion familiar to masons, cover lightly with water, 

 and then close the box or vessel to prevent the 

 water from evaporating. When making the Bordeaux 

 mixture, pour the requisite quantity of the stock 

 solution of sulfate of copper into the barrel, and 

 then dilute with four or five times the quantity of 

 water. Now add the lime, and then add enough 

 water to satisfy the formula. If the ferrocyanide 

 test is used, place a spoonful of the mixture in a 

 saucer or plate, and add a drop of the test solu- 

 tion. If a red color appears, the mixture needs 

 more lime. If the test solution is added directly 

 to a tank or barrel of the mixture, the color re- 

 action is apt to be lost in the mass. An excess 

 of lime ensures the safety of the mixture. 



10. How can one tell if soluble arsenic is jtrrsatf 

 in Paris green "I It is the soluble arsenic which 

 burns the foliage. This is present in London pur- 

 ple , but good Paris green should have little of it. 

 Farmers are always asking how they can determine 

 if Paris green contains soluble arsenic. This may 

 be determined by the use of the sulfur test. This 



