BASIC COPPER SULFATE AS A FUNGICIDE 125 



Cubic Inches in 1 Pound 

 Materia! Light Medium Heavy 



Calcium carbonate 91 72 47 



Basic magnesium carbonate 144 . . 64 



The light grades were employed as presumably offering greater surface area- 

 The fine ground crystalline forms are cheaper but more resistant and less satisfac- 

 tory. The solubility of both carbonates is low. Sodium carbonate, on the other 

 hand, is readily soluble, and the crystalUne sal soda with 10 molecules of water is 

 as serviceable as the anhydrous and monohydrated forms. Soda ash might also 

 be included if free from caustic alkali. Sodium carbonate is the least expensive, 

 followed by precipitated calcium carbonate and basic magnesium carbonate. The 

 cost, however, as with many other chemicals is largely dependent on the amount 

 purchased, size and kind of containers. 



The plan of operation adopted was based on complete precipitation of the 

 copper with a minimum of precipitant. Pickering had shown previously that 1 

 mol of copper sulfate required 0.7.5 mol of a divalent hydroxide. In the case of 

 cacibonates O.SO mol was invariably found necessary under the conditions 

 employed. The following tentative reactions are offered : 



Tribasic copper sulfate 

 4CUSO45H2O +.3.2CaC03= 4CuO.SOg.4H20+ 3CaS042H20 +0.2CaH2(CO3)3 



+2.80CO2-t-9.80H,O 

 4CuS04.5H20,+ 0.64 (4MgC03.Mg(OH),.5HoO) = 4CuO.SO3.4H2O + SMgSO^ 



+0.2MgH2(CO3)2+2.16CO2 + 19.64H2O 

 4CuS04.5H,0+3.2Na2C03 = 4CuO.SO3.4H2O + 3Na2SO4+0.4NaHCO3 + 2.80 



CO2 + 15.80HnO 



Telrabasic copper sulfate 

 5CuS045H20+4CaC03=.5CuO.S03.6H30+4CaS042H30+4C03 + llH20 

 5CuS045H20 + .8(4MgC03.Mg(OH)3.5H20) = 5CuO.S03.6H20 + 4MgS04 + 



3.2CO2+29.8OH2O 

 5CuS045H3O+4Na,CO3=5CuO.SO3.6H3O+4Na2S04+4CO., + 19H2O 



1 part by weight of CUSO4.5H2O requires: 

 0.32059 CaCO^ 



0.3112a 4MgC03.Mg(OH)o.5H20 

 0.339.57 NagCOa 



The amount of precipitant found necessary would point toward the formation 

 of tetrabasic sulfate (see Pickering), but as the amount of copper in the tri- and 

 tetrabasic sulfates with 4 and G molecules of water respectively is 54.055 and 54.240 

 per cent, differentiation has to be based largely on the sulfuric acid content 

 17.020 and 13.603 percent SO3. The analyses (page 127) of laboratory samples, 

 prepared under conditions far short of theoretical control, would seem to indicate, 

 however, that principally tribasic sulfate was formed together with more or less 

 hydroxide when excess precipitant was employed or the mixing was inadequate. 

 The 0.10 mol of precipitant (univalent) that did not react may represent the dilu- 

 tion at which the ionized sulfuric acid could not decompose the carbonates. 



With the insoluble carbonates, hot dilute copper sulfate solution is run slowly 

 into the suspended carbonate and stirred vigorously with a mechanical agitator 

 throughout the operation; but with soluble carbonates, the carbonate is let down 

 into the copper sulfate. The mix with insoluble carbonates should be slightly 



