REFRACTORY ORES.

New Zealand Herald, Volume XXV, Issue 9186, 16 October 1888, Page 5

REFRACTORY ORES.

NEW METHODS OF TREATMENT.

THE LATEST DISCOVERY.

PROFESSOR CROOKES' INVENTION.

A CHEAP PROCESS. [FROM OUR OWN CORRESPONDENT.] London, September 8. Professor Wμ. Ckookf.s claims to have made important improvements in the existing method of treating refractory ores in order to prevent a large percentage of the £old they contain _ being lost in the tailings. His plan is to subject crushed auriferous ores to the action of a solution of perehloride of iron with or without common salt in the presence of heat, either with the addition of nitrate of soda, nitrate of potash, or equivalent nitrate of peroxide of manganese or free mineral acid. The ore will be crushed in an ordinary battery as fine as possible, and will be passed in a slimy condition into a large tank capable of treating from '20 to ;\) tons at a time. The requisite chemicals will already be in the tank in a state of solution. When the ores contain only a small quantity of sulplmrets or other minerals attacked by perchloride of iron, Professor Crookes prefers to use a fairly strong solution of tne perchloride of about specific gravity lioO (which solution should not be neutral) and to that he would add as much common salt in crystals as the solution of perchloride of iron will dissolve in the cold. Common salt need only be used when silver is present in the ore in an appreciable percentage. To the mixture described he would add nitrate of soda or its equivalent, or well-washed precipitated per.oxide of manganese (Welden mud) in the_ proportion of one part of the peroxide of manganese to three parts of the perchloride of iron present -. or, in the case of the nitrates, one part of such oxidising element to five parts of the perchloride of iron. The whole should be heated to a temperature of iV>deg to 100' C. and should he continuously stirred. Should the gold he locked up in mineral matter that resists the action ot the perchloride of iron, the addition of peroxide of manganese or nitrate of soda would put the perehloride of iron into a state of unstable equilibrium, leaving the extra atom of chlorine available for tlu conversion of the gold into a chloride. The action of the process is to reduce the perchloride of iron to the state of a protoehloride, and the reconversion of that toperchloride constitutes the second branch of Professor Crookes' invention. When the ores contain other metals worth extracting besides gold and silver, Such as copper, cobalt, antimony, etc., an excess of the perchloride of iron solution should be used together with the common salt and peroxide of manganese, and the .solution should be treated almost to boiling. After the action has proceeded to n sufficient extent, the mixture should be allowed to settle, and the clear liquor drawn o:!'. or it may be clarified by filtration. The residue should then be washed. In precipitating the metals from the clear solution, copper should be used for gold, silver, etc.. and iron to precipitate the copper. The proctss will extract the gold from the gold ores iu their natural state, but when loaded with fsulpliurets or similar mineralised ores, it will be advantageous to roast them well, as the precious metals will be more easily extracted. The process may be employed in the gold ore as it comes from the mine (after tine pulverisation), but in jiost cases, when the gold is "free." and in ihe state removable by amalgamation, it is hest to subject the ore first to the ordinary treatment tor extracting the gold, and then to treat the concentrated sulphurets or taili::_-> by the new process, which is especially •u-ttul where the gold is associated with mineral matters which prevent the mercury from attracting the gold in the ordinary amalgamation process, owing to its " flouring " ur "sickening." The action of the common salt is to dissolve out the chloride of silver into which the silver has been converted by the action of the perchloride of iron. To revivify the spent solution of perchloride of iron, so as to render it available for further use in the treatment of auriferous ores, it is necessary to boil the spent solution of chloride of iron with an oxidising agent, such as nitrate of soda or other nitrate, or peroxide of manganese ami a little free mineral acid and common salt. The acid acting in the presence of the manganese or nitrate will liberate chlorine, which, unitine with the protoehloride of iron, will convert it into perchloride. By the addition of lime or chalk, and the application of air under pressure to the liquor, the manganese will be thrown down in the form of peroxide. I must apologise for these technicalities, hut tiie description of the process would be of no practical value to miners if the details were suppressed. Mr. Adoiphus Oppenheimer, ot Isew South Wales, the promoter of the Razorback Antimony Mining Company, has secured the Australian and New Zealand rights of the patent. He will start for the antipodes in about two months' time. It is not his intention to float a company to work the process, but he will be willing to arrange with any company desiring to use it. He states that by it iie can treat refractory ores for Ssper ton, while he asserts that the >~ewbery-\ autin proeess would probably cost from "20s to 30s. He declares that auriferous ores known to contain "Joz.s 4dwts of gold to tiie ton, have been subjected to treatment by Professor Crookes, who succeeded in recovering 2ozs 4dwts of gold Irom it. Mr. Oppenheimer's contention is that he can accomplish all that the NewberyVautin process achieves, but at a greatly reduced rate.