262 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



eau celeste from blue vitriol, Mohr's process is followed : Dissolve 3 lb. 

 of blue vitriol in hot water and add gradually, after cooling the solution, 

 1 lb. of soda ash, then 12 fi. oz. of ammonia of 24° B. ; dilute tlie blue 

 liquor to 100 gallons. The same liquor is obtained by adding sodium 

 carbonate to ordinary eau celeste or in mixing a solution of 1 lb. of blue 

 vitriol in 50 gallons of water, with 2 lb. of ammonium carb nate in 50 

 gallons of water. Liquors with an ammoniuret of oxide of copper 

 basis thus vary greatly, both as to strength and method of m inufacture. 

 When they are prepared it must not be forgotten that dry carbonate of 

 copper contains 51 per cent of copper, whilst blue vitriol which crystal- 

 lizes with 5 molecules of water, only contains 25 per cent. So that a 

 bouillie may have the same copper content twice as much blue vitriol 

 must be taken as copper carbonate. A bouillie bordelaise said to be 

 a 1 per cent bouillie, that is, made with 1 lb. of blue vitriol to 10 gallons 

 of water, ought to be compared in its cryptogamic action wnth a 1 per 

 cent ordinary eau celeste, and with a 0-5 per cent modified eau celeste 

 made from copper carbonate, these bouillies containing the same dose 

 of metallic copper. 



Properties. — Compared with bouillies eaux celestes have the great 

 advantage of being limpid solutions, containing neither precipitate nor 

 deposit capable of choking the spraying machines, or of being deposited 

 at the bottom of tanks or vessels. Eau celeste is more easily used than 

 bouillie bordelaise, the more so as it is made a long time beforehand in 

 a concentrated condition and can be kept indefinitely in that state. 

 Formerly, bouillie bordelaise contained a large excess of lime, which 

 rendered its application exceedingly difficult. Eau celeste had proper- 

 ties which had to be considered and which gave it a real advantage. 

 At that already distant time 5 per cent eau celeste ran much cheaper 

 than 2-3 per cent bouillie bordelaise. Eau celeste could also be more 

 uniformly distributed than thick bouillie. Finally, the adherence of 

 the thin pellicle of copper hydrate, which is formed after the evaporation 

 of the ammonia from the surface of the organs covered with liquor, is 

 much more perfect than that left by bouillie bordelaise, and resists, ac- 

 cording to Eossel, rains of seven to eight hours' duration. All these 

 advantages were of a nature greatly to encourage the use of eau celeste 

 at a time when bouillie bordelaise was not sufficiently studied. Now 

 it is otherwise. Carefully prepared, bouillie bordelaise does not now 

 contain an excess of lime ; it has no more than 0"5-l-0 per cent of 

 blue vitriol, and thus no longer has the great drawbacks of the original 

 bouillie bordelaise, so that all the comparative advantages of eau 

 celeste have almost disappeared. The advocates of eau celeste, 

 especially the ammoniaco-cupric liquor, and the modified eau celeste, 

 assert that eau celeste of this special composition is more active than 

 bouillie bordelaise, because it dissolves cellulose, and would thus, by 

 contact with the organs, disintegrate them and destroy them much 

 quicker than ordinary cupric bouillies. This opinion is very much 

 open to question. If it really were so, it would be easy to determine 

 the superiority of modified eau celeste and any other analogous prepara- 

 tion endowed with the extraordinary properties of Schweizer's reagent of 

 dissolving cellulose. In opposition to this enticing theory there must 



