PREPARATION OF THE COPPER SPRAYS. 149 



injiny b}' this .spray (p. 171). Tho unaltorod solution of the ooppor 

 sulpiiatc is not only iinploasant to handle and apply, and injurious to 

 tender vegetaljle tissues, but it is quite injurious to all metallic parts 

 of pumps, hose, extension rods, and nozzles, nozzles being- eaten out 

 very rapidly by it. For these various reasons the solution of 

 copper sulphate is rarely used as a spray in an unmoditied form. In 

 most cases its coiTosive action is more or less altered or neutralized 

 through the addition of some modifying agent. In other words, the 

 copper sulphate solution is used as a base or stock solution for the 

 preparation of several more or less noninjurious and ecpially effective 

 sprays, as the Bordeaux mixture, the eau celeste, the modified eau 

 celeste, the ammoniacal copper car})<)nate, etc. For this purpose it 

 may be prepared in a concentrated solution, to be used as a stock 

 solution for the preparation of any of the modified sprays mentioned, 

 as already pointed out. 



A convenient strength for stock solutions is 1 pound of copper sul- 

 phate to 1 or 2 gallons of water. In using stock solutions, two matters 

 should always be considered: (1) The pails, barrels, or tanks used 

 should be carefully gauged and marked, so that thii number of gallons 

 of water or of the solution they contain may be known and not guessed 

 at.^ (2) Before dipping from a stock solution an}' required number 

 of gallons, the solution should ])o, thoroughly stirred, otherwise the 

 last dipped out will be very much stronger than that coming from the 

 top, and consequently the work will be inaccurate and often very 

 unsatisf actor}' ; moreover, neglect of this precaution might, in many 

 cases, lead to the injury or even to the destruction of the plants 

 treated. It may also be said that the copper sulphate solution should 

 be cold when used in th(», preparation of Bordeaux mixture, eau celeste, 

 modified eau celeste, or ammoniacal copper carbonate. 



BORDEAUX MIXTURE. 



Bordeaux mixture is prepared by uniting the milk of lime with a 

 solution of copper sidphate. The reaction which takes place when 

 the two solutions are united as well as the other chemical phases 



' The following rules for measuring square and round tanks and casks may prove 

 of value in this connection: 



Circular cisterns. — Multiply the square of the diameter in feet by the depth in feet 

 and the product by 5| for the contents in gallons. 



Circular casks or barrels. — Multiply the square of the average diameter in inches by 

 34, and that by the height in incites, and point off four figures. The result will be 

 the contents in gallons and decimals of a gallon. The average diameter of a barrel 

 may usually be obtained by adding the greatest diameter to the least diameter and 

 dividing by 2. 



Square tanks. — Multiply the width in feet by the length in feet, and that by the 

 depth in feet, and that again by Tj^o; which will give the contents i^i gallons. 

 Another and simple method is to multiply the length, width, and depth in inches, 

 and divide by 231, which will also give the contents in gallons. 



