21 



used. First insert the blade of a penknife in the mixture, allowing it to remain there 

 for at least one minute. If metallic copper forms on the blade, or, in other words, 

 if the polished surface of the steel assumes the color of copper plate, the mixture ia 

 unsafe and more lime must be added. If, on the other hand, the blade of the knife 

 remains unchanged, it is safe to conclude that the mixture is as perfect as it can be 

 made. As an additional test, however, some of the mixture may be poured into an 

 an old plate or saucer, and while held between the eyes and the light the breath 

 should be gently blown upon the liquid for at least half a minute. If the mixture is 

 properly made, a thin pellicle, looking like oil on water, will begin to form on the 

 surface of the liquid. If no pellicle forms, more milk of lime should be added. 



If spraying is to be done upon a large scale, it will be found much more convenient 

 and economical in every way to prepare what are known as stock solutions of both 

 the copper and lime. To prepare a stock solution of copper sulphate, procure a barrel 

 holding 50 gallons. Weigh out 100 pounds of copper sulphate, and after tying it in 

 a sack suspend it so that it will hang as near the top of the barrel as possible. Fill 

 the barrel with water, and in two or three days the copper will be dissolved. Now 

 remove the sack and add enough water to bring the solution again up to the 50-gallon 

 mark, previously made on the barrel. It will be understood, of course, that this 



Fig. 1.— Making Bordeaux mixture; Pouring together the lime milk and copper sulphate solution. 



second adding of water is merely to replace the space previously occupied by the 

 sack and the crystals of copper sulphate. Each gallon of the solution thus made will 

 contain 2 pounds of copper sulphate, and, under all ordinary conditions of tempera- 

 ture there will be no material recrystallization, so that the stock i>reparation may be 

 kept indefinitely. 



Stock lime may be prepared in much the same way as the copper sulphate solution. 

 Procure a barrel holding 50 gallons, making a mark to indicate the 50-gallon point. 

 Weigh out 100 pounds of fresh lime, place it in the l:)arrel, and slack it. When 

 slacked, add sufficient water to bring the whole mass up to 50 gallons. Each gallon 

 of this preparation contains, after thorough stirring, 2 pounds of lime. 



When it is desired to make Bordeaux mixture of the 50-gallon formula it is only 

 necessary to measure out 3 gallons of the stock copper solution, and, after thorough 

 stirring, 2 gallons of the stock lime; dilute each to 25 gallons, mix, stir, and test as 

 already described. One test will be sufficient in this case. In other words, it will 

 not be necessary to test each lot of Bordeaux mixture made from the stock prepara- 

 tions, provided the first lot is perfect and no change is made in the quantities of the 

 materials used. Special care should be taken to see that the lime milk is stirred 

 thoroughly each time before applying. As a final precaution it will be well to keep 

 both the stock copper sulphate and the stock lime tightly covered. 



