CHAPTEE XIV. 



COPPER HYDRATE— BOUILLIE BORDELAISE— BOUILLIE 

 BOURGUIGNONNE. 



91. Copper Hydrate (Bouillie Bordelaise). — Preparation. — 



By precipitating a soluble salt of copper, by caustic alkali, or by milk 

 of lime. 



CuSO, + 2NaOH = Cu(OH), + Na^SO, 

 Copper Sodic Cupric Sodic 



sulphate. hydrate. hydrate. sulphate. 



CuSO, + Ca(OH), = Cu(OH,) + CaSO, 



Copper Calcium Copper Calcium 



sulphate. hydrate. hydrate. sulphate. 



The bouillie bordelaise is prepared by the second reaction ; it is 

 a mixture of hydrated oxide of copper and sulphate of lime, and gener- 

 ally contains an excess of lime. Its composition and its concentration 

 vary much. 



Preparation of a Normal Bouillie Bordelaise. — A solution of 

 "blue vitriol is prepared on the one hand, and on the other hand a milk 

 of hme carefully rubbed up with water. 



1. Blue Vitriol. — This salt should be as pure as possible. It 

 should be dissolved in wooden, copper, glass, or stoneware vessels; 

 those of tin and iron should be avoided, as these metals decompose 

 blue vitriol. To facilitate solution of blue vitriol it is placed in a basket 

 or pocket of wire gauze, in a vessel filled with rain water, so that it 

 ■dips into it completely, but as near the surface of the liquid as possible. 

 Solution is complete in twelve hours. If pressed for time blue vitriol 

 may be dissolved in a little warm water and this solution run into the 

 receiver containing the remainder of the water required to make the 

 "bouillie. It is necessary to use a cold solution of blue vitriol in making 

 the mixture, for with hot solutions there would be formed, along with 

 the granular hydrated oxide of copper, some inert black oxide of 

 <;opper. 



2. Milk of Lime. — The lime should be fat lime in lump. This 

 .quicklime is slaked by adding water gradually. As soon as it is slaked 

 it is beaten up in cold water to form milk of lime. This milk of lime 

 is passed through a fine sieve, to separate the impurities present in all 

 limes. To obtain a fine, gelatinous, homogeneous precipitate, having 

 a maximum adherence to the leaves it is advisable to mix these two 

 liquids as follows : The milk of lime is run slowly, in a fine stream, 

 into a cold solution of blue vitriol, stiiring constantly, or better still, 

 run the two solutions simultaneously and slowly into a third vessel, 



(227) 



