Materials and Formulas. 137 



said to increase the adhesive power of the Bordeaux mixture 

 when the two are applied together. 



The resin preparations and arsenical compounds have been 

 successfully united and applied, but such combinations are at 

 present little used. 



COPPER ACETATE ; VERDET ; VERDIGRIS. There are sev- 

 eral compounds of copper and acetic acid, but the one which 

 has been used in spraying is known as the dibasic acetate of 

 copper. It possesses only fairly good fungicidal properties, but 

 it has been highly recommended for its adhesion to foliage. It 

 may be applied at the rate of 2 to 4 ounces in about 25 gallons 

 of water. 



COPPER ARSENITE. See SHEELE'S GREEN, page 120. 



COPPER CARBONATE; CARBONATE OF COPPER; CuCO 3 . 

 Chester's method of preparing this chemical is as follows: 

 " Dissolve in a barrel 25 pounds of copper sulphate in hot 

 water. In another barrel dissolve 30 pounds of sal-soda. 

 Allow both solutions to cool, then slowly pour the solution of 

 sal-soda into the copper sulphate solution, stirring the same. 

 Fill the barrel with water and allow the precipitate of copper 

 carbonate to settle. Upon the following day siphon off the 

 clear supernatant liquid, which contains most of the injurious 

 sodium sulphate in solution. Fill the barrel again with water, 

 and stir the precipitate vigorously into suspension ; again allow 

 the precipitate to settle, and again on the following day siphon 

 off the clear liquid. The operation washes the carbonate free 

 of most of the sodium sulphate which contaminates it. Make 

 a filter of stout muslin, by tacking the same to a square wooden 

 frame which will just fit over the open top of the second barrel, 

 letting the muslin hang down loosely so as to form a sack ; 

 through this filter the precipitate, so as to drain off the excess 

 of water, and as the filter fills remove the precipitate, and allow 

 it to dry in the air, when it is ready for use. The operation 

 is not troublesome, and can be carried on in connection with 

 other work." 1 The following reactions are at present supposed 

 to take place when the two solutions are united: 2 12 (CuSO 4 , 

 5H,0) + 12 (Na 2 C0 8 , 10H,O) = 6 [CuCO 3 , Cu(OH) 9 , H 2 O] + 

 12 Na 2 SO 4 + 6 CO 2 + 168 H 2 O. 



1 Ann. Kepi. U. S. Com. Agric. 1890, 403. 



2 Del. Agric. Exp. Sta. kth Ann. Kept. 1891, CT. 



