126 MASS. EXPERIMENT STATION BULLETIN 254 



alkaline to litmus and free from soluble copper (ferrocyanide test), basic copper 

 carbonate, and oxidation products at the completion of the reaction. A neutral 

 to slightly acid mix with a trace of soluble copper is more dependable when sodium 

 carbonate is used and likely to yield a better product. The relative concentra- 

 tion, temperature, rate of addition and agitation should be so coordinated as to 

 give a basic sulfate of the best physical characteristics possible. Similar results, 

 however, may be obtained from different correlations. Allowing the precipitate 

 to stand before filtering affects the bulk and increases the amount of carbonate, 

 both of which are objectionable. The presence of iron in the copper sulfate also 

 appears to injure the physical properties. A properly prepared basic sulfate is 

 soft, pulverulent between the fingers, and free from grit and requires no grinding 

 except the disintegration of the cake from the filter. Subsequent air separation, 

 however, improves the physical properties especially for dusting purposes. 



Commercial Preparation 



The directions recently furnished a manufacturer for the preparation of basic 

 sulfate with calcium carbonate are practically the same as originally published 

 except as to size of the batch and the elimination of the excess precipitant. In 

 adapting a laboratory process to factory conditions there is likely to be some loss 

 in quality due to the limitations imposed by economic production. 



1890 grams (4.17 lbs.) of copper sulfate, substantially free from iron, in 10 gallons of solution, 

 heated to 80°C, are added gradually to 606 grams (1.34 lbs.) of light, precipitated calcium 

 carbonate, suspended in 5 gallons of water, at 80°C, stirred vigorously for 30 minutes (includ- 

 ing the time of precipitation) at 80°C, filtered immediately, washed practically free from 

 soluble by-products, and dried at a relatively low temperature (35-50°C) to a soft, light, bulky, 

 free-flowing, bluish powder of fine particles having a "fair" power of suspension and adhesive- 

 ness and containing about 26.50% of metallic copper. 



The above batch yields nearly 4 pounds of material. Some of the gypsum is 

 lost in the filtrate. 



The method for preparing basic copper sulfate with precipitated basic magne- 

 sium carbonate is substantially the same as with calcium carbonate except that 

 only 588+ grams (1.30 lbs.) are required when the carbonate holds true to formula. 

 A preUminary trial with a few grams of material is advisable, however, to establish 

 the proper ratio. Discoloration (blackening) is more likely to occur than with 

 calcium, probably due to the basic portion of the carbonate. The discolored 

 portion absorbs carbon dioxide rapidly on exposure to the air and is apparently 

 converted into a blue basic carbonate which is considered inferior to the basic 

 sulfate. The basic sulfate is a relatively pure, soft, blue, free-flowing powder of 

 fine amorphous particles and contains about 53 per cent of metallic copper as the 

 by-product, magnesium sulfate, is readily removed by washing. The batch yields 

 about 2 pounds of material. 



The method for preparing basic copper sulfate with sodium carbonate differs 

 considerably from the calcium carbonate process in the concentrations employed, 

 in the direct addition of the precipitant to the copper sulfate, and in the control 

 necessary to coordinate the rate of addition with the efficiency in mixing. An 

 undue concentration of the sodium carbonate causes the formation of a deep blue 

 precipitate or a brown precipitate that absorbs carbon dioxide from the air and 

 becomes more or less hard and gritty. 



963 grams (2.12 lbs.) of anhydrous sodium carbonate (or 1127 grams (2.48 lbs.) of Na^COj 

 IHjO, or 2600 grams (5.73 lbs.) of NajCOalOHaO) in 10 gallons of solution, heated to 70°C 

 are added gradually to 2836 grams (6.25 lbs.) of copper sulfate in 5 gallons of solution at 

 70°C, stirred vigorously for 30 minutes (including the time of precipitation) at 70°C, filtered 

 immediately and washed practically free from sodium sulfate and dried at a relatively low 

 temperature (35-50°C) to a soft, adhesive, greenish-blue powder of fine amorphous particles 

 containing about 53 per cent of metallic copper. 



