Materials and Formulas. 129 



lime. The adhesive properties are perhaps greater than those 

 of any of the other mixtures of this nature, and there are thus 

 several features which recommend the method for general use. 

 But the season of 1894 showed that the preparation is not a very 

 safe one to use except in dry seasons, or in regions where the 

 rainfall and dew are but slight. In the presence of much water, 

 the mixture will injure both foliage and fruit, whatever may be 

 the compound doing the mischief, and for this reason when so 

 prepared it cannot be unqualifiedly recommended. In some sea- 

 sons it may be used with impunity, while in others it may cause 

 a loss which will more than overbalance any advantage derived. 

 The ferrocyanide of potassium test, is of great value in deter- 

 mining how much lime is actually required, and in this manner 

 it may serve as a check when the ingredients are not weighed, 

 and then this neutral condition may be taken as a starting-point 

 for the addition of more lime. 



In making the Bordeaux mixture by the aid of the ferrocya- 

 nide of potassium test, certain points must be borne in mind in 

 dissolving the copper sulphate. (See, also, COPPER SULPHATE.) 

 A definite proportion should exist between the amount of the 

 salt used and the water in w r hich it is dissolved. This is 

 necessary so that the amount of the copper compound in a 

 given amount of water may be known. The more common 

 method is to dissolve either 1 or 2 pounds of copper sulphate 

 in 1 gallon of water. Any desired amount can then easily be 

 obtained by first stirring the stock solution thoroughly, and 

 then taking out the quantity which holds the desired amount. 

 The milk of lime is then added to the diluted solution until a 

 few drops of the dissolved ferrocyanide of potassium (which 

 see) give no brown discoloration when added to the mixture. 

 A better way of using the test, however, is to add some of the 

 mixture to a few drops of the solution, the latter being held in 

 a butter dish or other article of white porcelain. This will 

 show the presence of the red precipitate when it cannot be 

 detected by the old method of adding the test solution to the 

 mixture. It is probable that much of the injury which fol- 

 lowed the use of the Bordeaux mixture in 1894 was caused by 

 an insufficient amount of lime having been used, this being due 

 to the fact that the ferrocyanide of potassium test did not show 

 plainly the true condition of the preparation. A person ex- 



