NATURE AND SOURCE OF SPRAYING MATERIALS. 183 



Water dniining- from copper mines sometimes carries copper sulphate 

 in solution, in which case the crystals are procured by evaporating- the 

 excess of water. Barrels of copper sulphate weigh from 300 to 600 

 poiuids. 



The manufacturer's price of copper sulphate will depend largely 

 upon the price of copper and sulphuric acid — two leading constituents, 

 as they are sold in the market — and upon supply and demand. The 

 cost to the manufacturer will not, however, necessarily depend upon 

 the market \alue of copper and acid, for one or both may be obtained 

 ])y him as by-products in other regular and profitable lines of manu- 

 facture, such as the smelting of gold and silver ores, etc.^ 



COPPER CARBONATE. 



Copper carbonate as usually prepared shows the following formula: 

 CuCOj. CuHjOo. It is widely used in the preparation of ammonl- 

 acal copper carbonate sprays, and is especially well adapted to the 

 treatment of maturing fruit where subject to fungous diseases. As 

 commonly sold on the market, the carbonate of copper is green and 

 finely granular or powdery. It contains about 57.4 per cent of cop- 

 per. Native minerals of similar composition occur, such as malachite 

 and azurite. 



Copper carbonate is manufactured by a number of firms in the 

 United States, but much less extensively than the sulphate. In most 

 cases it is prepared by adding to a solution of copper sulphate an 

 excess of sodium carbonate (sal soda) in solution. This gives a floc- 

 culent mixture of pale blue color, afterwards changing to green. 

 Heating makes the precipitate more granular. 



Owing to the difficulty of obtaining carbonate of copper in smaller 

 towns, as well as the high price usually charged for it, the Depart- 

 ment has usually recommended that the fruit growers prepare it. 

 The following instructions for this work were published by the writer 

 in a circular sent to the peach growers of the country in 1894—95: In 

 a barrel dissolve 6 pounds of copper sulphate in 4 gallons of hot 



^ Owing to the somewhat enhanced value of copper at this time (March, 1899) , the 

 wholesale price of copper sulphate has advanced. San Francisco producers quote copper 

 sulphate in barrels, f. o. b., at 5} cents, and carload lots at 5 cents per pound; Omaha 

 quotations are, by the ton or carload, 5j cents; one New York firm quotes 5| cents 

 by the barrel or ton and 5j cents by the carload, and a second firm quotes 6 cents by 

 the barrel, 5^^ cents by the ton, and 5f cents by the carload; Denver quotations are 

 6 cents by the barrel, 5| cents by the ton, and 5^ cents by the carload; Cleveland 

 quotes 6 cents per pound in any quantity; one Philadelphia firm quotes 6 cents by 

 the barrel, 5| cents by the ton, and 5| cents by the carload, and a second firm quotes 

 5| cents by the barrel, 5 J cents by the ton, and 5^ cents by the carload; Baltimore 

 quotes 5| cents by the barrel, 5h cents by the ton, and 5} cents by the carload; Great 

 Falls, Mont., quotes 4| cents per pound in carload lots and 5 cents per pound for less 

 than carload lots, etc. 



