Year: 1875

through reverberation. the silver it con

 tains passes with 1t to the same state and as the sulphate of lead is insolu

 ble, the silver escapes during the sub sequcnt reactions and is thus lost The quantity which converts itself into chloride during the rcyerberation l: small, as is easily shown by reverberat ing silver bearing galena with salt, test ingthe reverbera,cd ore with hot water Altering and testing the latter with io dide of potash. or another of the reac tives which indicate its presence in tine dissolutious.

 The arsenic mechanically helps tow ards the loss of silver, for as the arsen- ic acid Is tolerably vOlitile it carries away silver with it, which remains de posIted in the chambers of cOndensa- ton, il being known that more silver is left in these deposits made by arsen- ical ores. Some intelligent men main tain that the arsenic is pernicious in the process, because it forms with the silver insoluble arseniatum of silver but perhaps they did not recollect that thc arsenica! acid decOmpOses itself with the dark red heat and converts itself into arsenical acid, and that therefore it's formation during the re- verberation is not probable Anthony acts in q similar way to arsenic.

 Great care must be taken to avoid the formation of clots, as the metal which remains in their inside escapes the reactions which is the object of re- yer5eration and a loss of silver is thus caused. These clOts must be separat ed, ground, mixed with two or three per cent. of salt and reverberated again with tine ore placed on the first hearth

 Preparation of the hyposulphite of lime and sulphIde of calcium, used to dissolve the chloride of silver and then to precipitate the silver in the state of sulpbide.

 As I have before indicated in pro cess used by Patera, It is advised to dis solve the chloride of silver with hypO- sulphite of soda; but as it is easier to procure hyposulphate of lime, and this is also cheaper, preference was given to the latter dissolvent which further more is as energetic as that of soda

 As is known, the preparation of hy- posuiphates Is effected by converting first the metal that is Co serve as base into -ulphide and boiling then the sul- phide with sulphur. The process used for the preparation of hyposulphite of lime is different. For g space of four hours boil one part of lime with one third its weight of powdered sulphur and four parts of clean water; the lime converts i.self into hyposulphite of lime and into sulphide of calcium.

 This mass is then treated with a so- lution of Sulphatc or chloride of cop per; the copper is precipitated into the state of a sulphide and the lime re- mains dissolved in the state of hyposul- phi;e. But it is necessary to take care not 10 put in an insufficient quantity of suipha,e for the complete decomposi- tion of the sulphide of calcium, for whatever quantity of this compound might remain in the dissolution of the hyposulphite would convert the chlo- ride of silver into sulphide of silver and would naturally cause loss; the same would occur by using chloride of copper; but with the sulphate there is still another reason of loss which consists in the sulphate of lime being insoluble, while more sulphate of cop per is used in a larger quantity of hy- posuIphatc being decomposed, and al- though through the change of ele ments hyposulphite of copper would be formed, that would not have upon the chloride of silver the same dissolv- Ing power as that of the alcalinic or metals. The chloride of copper does not in this iniure the operation in the least, but as it is of value, 1t is better not to use it to excess.