280 INSECTUI])ES, FI'NGICIDES, AND WEED KILLERS. 



are laid on supports in a stove heated to 30° C. After twenty-foul- 

 hours the supports are dipped into water at 30° C. (86' F.), where 

 they remain four to five days. This steeping is repeated five to six 

 times. The green crust of verdigris has then dissolved the copper and 

 fornaed a blue mass of basic acetate of copper. It suffices to scrape 

 this crust, which is commercial verdigris. It comes to market in two 

 forms : (1) As a product containing no moisture, and termed Verdet gris 

 extra sec, containing 34-35 per cent of copper. (2) As a still moist 

 product, containing 25-42 per cent of water, and termed Verdet gris 

 sec mcrchand. The latter being of variable composition, and as buyers 

 must have a definite product, it is the Verdet gris extra sec which is 

 used in the preparation of the bouillie. It is sold as balls, cakes, or 

 grains. To prepare the bouillie, it suffices to crush the verdigris, mix 

 it with a little water, macerate it for some daj^s, and then dilute it to a 

 suitable consistency. 



Properties. — Verdigris is amorphous. But it swells in a little 

 water after a few hours ; forming a viscous paste beaten up with much 

 water dibasic acetate of copper splits up into soluble copper acetate 

 and insoluble cupric hydrate, which forms a blue flaky precipitate with 

 the properties of bouillie bordelaise. Bencker believes this precipitate 

 remains flaky for a longer time, and thus keeps itself suspended longer 

 than bouillie bordelaise. The verdigris bouillie has the properties of 

 bouillie bordelaise and blue vitriol. The deposit of hydrated oxide of 

 copper which it contains covers the leaf with a protective layer of 

 insoluble copper oxide, and the solution of copper acetate acts like 

 solutions of all soluble copper salts in an immediate and very energetic 

 manner on the spores of fungi as well as on the plant itself. This 

 soluble portion of the verdigris copper acetate would in fact produce 

 burns if care were not taken to use sufficiently dilute bouillies. Now 

 the dose of soluble copper acetate present in a verdigris bouillie is not 

 sufficient in most cases to corrode the organs touched by spraying, and 

 plants suffer comparatively little by this treatment. However, plants 

 sensitive to dilute solutions of blue vitriol and to cupric hydrate deposited 

 on the surface of their leaves will, after spraying with this l)ouillie, be 

 poisoned to the same extent and suffer the sanie damage, followed by 

 partial and even total fall of the leaves, as is the case with ordinary 

 peaches and certain species of rose bushes. Bencker, Girard, Chuard, 

 and Porchet found that the adherence of the cupric hydrate of the verdi- 

 gris bouillie is superior to that of other bouillies. It must not be forgotten, 

 however, that the cupric hydrates behave in the same manner in all 

 bouilbes if these are prepai-ed and used rationally. If bouillie borde- 

 laise formerly adhered badly, compared with bouillies with a verdigris 

 basis, it is not the case now with bouillie bordelaise used immediately 

 after its preparation. A neutral bouillie bordelaise, a bouillie borde- 

 laise celeste, eau celeste ^nodifiee, verdigi'is bouillie, and Ferret's bouillie 

 have many analogies to each other. Their adherence, so to speak, is 

 the same, and their anticryptogamic energy almost identical. Careful 

 study of this point has shown that the tendency of copper salts to 

 poison plants as well as their anticryptogamic energy is perceptibly 

 proportionate to their copper content. The action is inversely pro- 



