238 AGRICULTURAL EXPERIMENT STATION. [Jan. 



water. When they are wholly dissolved, add the solution 

 to enough water to make the whole quantity fifty gallons. 

 This preparation has been found to be better and cheaper 

 than that made according to the original formula, which is 

 as follows : Dissolve three ounces carbonate of copper in 

 one quart aqua ammonia (22° B.),* and add the solution to 

 twenty-five gallons of water. 



Dr. Thaxter, formerly of the Connecticut Experiment 

 Station, has suggested that a very large saving may be made 

 by preparing the carbonate of copper by the following 

 method, instead of buying it, as its market price is much 

 greater than that of the materials necessary for its prepara- 

 tion : Take two pounds of sulphate of copper and dissolve 

 it in a large quantity of hot water ; in another barrel or tub 

 dissolve two and one-half pounds of carbonate of soda (sal- 

 soda) in hot water. When both are dissolved and cooled, 

 pour the soda solution into the copper solution, stirring 

 rapidly. There will result a blue-green precipitate of car- 

 bonate of copper, which must be allowed to settle to the 

 bottom of the vessel. Now draw off the clear liquid above 

 the sediment, fill the vessel with fresh water and stir up the 

 contents thoroughly. After the copper carbonate has once 

 more settled to the bottom, again draw off the clear fluid 

 above. The carbonate may now be removed from the vessel 

 and dried, when it is ready for use. From the amount of 

 blue-stone and sal-soda given above will be produced one 

 pound of copper carbonate, and the amount of each neces- 

 sary to produce any given amount of copper carbonate is 

 easily calculated. 



Sulphate of copper is used in solutions of varying strength 

 for certain special cases. 



Sulphide of potassium, known also as sulphuret of potas- 

 sium or liver of sulphur, has been found useful in the treat- 

 ment of diseases caused by those fungi known as powdery 

 mildews, especially on plants grown under glass. It is 

 ordinarily used in the proportion of half an ounce of the 

 sulphide to one gallon of water. 



* Dealers usually handle ammonia water of a strength of 24° B. (= 22.5* am- 

 monia) or of 26° B. (=26.5* ammonia). To reduce these to the required strength, 

 22° B. (= 19^ ammonia), add four parts of water to ten of aqua ammonia of 26°, or 

 two parts of water to ten parts of 24° aqua ammonia. 



