APPENDIX. 425 



So much depends upon the correct preparation of bordeaux mixture that 

 we quote in full the directions for its preparation which are given by Doctor 

 Galloway of the United States Department of Agriculture: 



" It has been found that the method of combining the ingredients has an 

 important bearing on both the chemical composition and physical structure 

 of the mixture. For example, if the copper sulphate is dissolved in a small 

 quantity of water and the lime milk diluted to a limited extent only, there 

 results, when these materials are brought together, a thick mixture, having 

 strikingly different characters from one made by pouring together weak 

 solutions of lime and copper sulphate. It is true, furthermore, that if the 

 copper sulphate solution and lime milk are poured together while the latter 

 or both are warm, different effects are obtained than if both solutions are 

 cool at the moment of mixing. 



"Briefly, the best results have been obtained from the use of the bordeaux 

 mixture made in accordance with the following directions : In a barrel or 

 other suitable vessel place twenty-five gallons of water. Weigh out six 

 pounds of copper sulphate, then tie the same in a piece of coarse gunny sack 

 and suspend it just beneath the surface of the water. By tying the bag to a 

 stick laid across the top of the barrel no further attention will be required. 

 In another vessel slack four pounds of lime, using care in order to obtain a 

 smooth paste, free from grit and small lumps. To accomplish this it is best 

 to place the lime in an ordinary water pail and add only a small quantity of 

 Avater at first, say a quart or a quart and a half. When the lime begins to 

 ora'jk and crumble and the water to disappear add another quart or more, 

 exercising care that the lime at no time gets too dry. Toward the last con- 

 siderable water will be required, but if added carefully and slowly a per- 

 fectly smooth paste will be obtained, provided, of course, the lime is of good 

 quality. When the lime is slacked add sufficient water to the paste to bring 

 the whole up to twenty-five gallons. When the copper sulphate is entirely 

 dissolved and the lime is cool, pour the lime milk and copper sulphate solu- 

 tion slowly together into a barrel holding fifty gallons. The milk of lime 

 should be thoroughly stirred before pouring. The method described insures 

 good mixing, but to complete this work the barrel of liquid should receive 

 final stirring, for at least three minutes, with a broad wooden paddle. 



"It is now necessary to determine whether the mixture is perfect — that 

 is, if it will be safe to apply it to tender foliage. To accomplish this, two 

 simple tests may be used. First insert the blade of a jjenknife 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 is 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 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 pi-operly 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. 



