THE PREPARATION AND EFFECTIVENESS OF BASIC 

 COPPER SULFATE AS A FUNGICIDE 



By E. B. Holland, Research Professor of Chemistry, C. O. Dunbar and 

 G. M. Gilligan, Research Assistants in Chemistry, and 

 W. L. Doran, Research Professor of Botany 



Basic copper sulfates are insoluble copper compounds resulting from the 

 action of alkali or alkaline earth hydroxides or carbonates, short of saturation 

 upon copper sulfate, although other precipitants are occasionally employed. 

 The reaction has been studied by numerous chemists as shown in a previous paper 

 (6 p. 741i 74-) '> but the lack of agreement, as a whole, tended to indicate the 

 production of mixtures rather than a definite compound. When, however, the 

 amount of precipitant was sufficient for complete precipitation of the copper, 

 or nearly so, tribasic sulfate, 4CuO.SO,.4H20, was frequently obtained. Proust 

 (12 p. 34) prepared the compound with fixed alkalies; Kane (7, p. 270), with insuffi- 

 cient ammonia or potassium hydroxide; Smith (15, p. 498), with insuffi- 

 cient fixed alkalies and with sodium carbonate; Vogel and Reischauer (16), with 

 ammonia" Field (5, p. 124), with insufficient fixed alkahes; and Pickering (10, 

 n 1982 ; 11, p. 1855), with fixed alkalies and with alkaline earths. More recently 

 Bell and Taber (1, p. 173) and Young and Steam (18, p. 1951, 1952) failed to 

 obtain a definite salt by the phase rule, and WilUamson (17, p. 790) secured 

 unsatisfactory results but substantially the tribasic. Britton (3, p. 2152, 2153) 

 bv an electrometric determination with an oxygen electrode obtained a sodium 

 hydroxide equivalent of 1.47 for copper sulfate wliich would indicate approxi- 

 mately 4CUO.SO3. The alkali was added slowly with thorough agitation in 

 order to secure the formation of an amorphous precipitate. With a copper elec- 

 trode Britton (4, p. 2798) obtained an equivalent of 1.50 and by phase rule studies 

 at 25° (4, p. 2800-2802) established a formula of 4CuO.SO3.4H2O. Bell and 

 Murphy (2) by varying the quantity of copper sulfate with a given amount of 

 copper oxide obtained in 8 hours at 100°C a neutral solution and the same basic 

 sulfate. The results of Kruger (8) and Sabatier (14) tend to confirm the formula. 

 The minerals brochantite and langite are said to be tribasic sulfates with three 

 and four molecules of water respectively. Smith (15) obtained tetrabasic sulfate 

 (5CuO.SO3.6H2O) short of alkalinity; and Pickering (10, p. 1982; 11, p. 1855), 

 by adding alkali or alkaUne earth hydroxide sufficient for initial alkalinity (1.60 

 mols). Nelson (9, p. 1189) obtained a basic sulfate of 7CUO.2SO3 previously 

 reported by Proust (12, p. 34). 



Preparation of Basic Copper Sulfate 



With the exception of the prehminary experiments carbonates have been used 

 as precipitants in the Station laboratory in preference to the hydroxides. The 

 carbon dioxide evolved in the reaction prevents decomposition (blackening) in a 

 measure, and the leavening effect of the gas seems to improve the physical condi- 

 tion of the resulting product. Precipitated calcium carbonate (CaCOg), precipi- 

 tated basic magnesium carbonate (4MgC03.Mg(OH)2.5H20) and sodium car- 

 bonate (NaaCOg) have been employed for the purpose. The following commer- 

 cial grades of precipitated calcmm and magnesium carbonates are available accord- 

 ing to the distri butor: 



'Reference is made by number to Literature Cited, p. 148. 



