182 PEACH LEAF CURL: ITS NATURE AND TREATMENT. 



may often be purchased at a somewhat lower figure than a purer 

 article. Spraying tests have been made by the writer for the com- 

 parison of pure commercial bluestone with that obtained asji by-prod- 

 uct of smelting works, and which contained a considerable amount of 

 iron, and the results showed that the latter article contained fully as 

 great fungicidal value as the former. 



The manufacture of copper sulphate is carried on at a considerable 

 number of establishments in the United States, and various processes 

 are followed. ■ A large amount of this chemical is also imported, 

 chiefly from England. 



Bluestone is prepared by dissolving cupric oxide in sulphuric acid, 

 or by oxidizing the sulphide of copper, the latter being the cheaper 

 process. Mr. Alfred Rapp, a gentleman who has enjoyed a wide 

 experience, has kindly supplied the following facts respecting the 

 manufacture' of copper sulphate by a leading smelting firm of the 

 Pacific coast. He states that the copper is mainly derived from mattes 

 produced in the blast furnaces, and, secondly, from an acid solution 

 of sulphate of copper resulting from the precipitation of silver by 

 metallic copper out of a sulphate solution. To bring the copper in the 

 different mattes in solution they are first crushed and pulverized to 

 about one-thirty -second of an inch or finer, and subjected to a roasting 

 process by which the sulphur is nearly all oxidized. The roasted 

 matte contains the copper as oxide and partly as sulphate, with a small 

 amount still as sulphide. This material is pulverized once more and 

 fed into lead-lined leaching tanks, where the acid copper sulphate 

 solution is added, and, if necessary, sulphuric acid. The whole mass 

 is heated by steam running through lead pipes. The copper oxide 

 and the copper sulphate in the roast is thus brought in solution as a 

 sulphate. About 8() per cent of the copper contained in the mattes is 

 thus leached out. The resulting solution, of course, is not a neutral 

 one, but still contains an excess of free sulphuric acid. This solution 

 is transferred to other lead-lined tanks, containing, suspended from 

 wooden sticks, strips of lead about 3 inches wide, the central portion 

 of which is bent downward between the sticks so as to form a loop, 

 which is held by the ends of the lead strips being bent over the sticks. 

 The copper sulphate when run down to these crystallizing tanks is 

 about 36^ to ■i-i'^ B. During the cooling process, which takes about 

 four to seven days, the copper sulphate, or rather part of it, separates 

 out of the solution as blue crystals, which are deposited upon the 

 strips of lead. These crystals are dried and packed in barrels ready 

 for the market. This, Mr. Rapp adds, is the general way in which 

 bluestone is made the world over, except that they have at the works 

 considered, in addition to the copper in the mattes, the acid copper 

 sulphate solution from a silver refinery. 



