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immediately clear. Results of tests indicate that the advantage of using sulph-hydrate, as compared with the normal sulphide, was not enough to make the separate preparation of the sulph-hydrate worth while.

ACTION OF SULPHIDES OF SODIUM ON THE ORE.

When a solution of any of these compounds is applied to ground ore, the ore slowly turns black. Slightly better results in the flotation were obtained when the ore was allowed to stand long enough to become thoroughly blackened by the sodium sulphide. The artificial lead sulphide, on standing, finally assumed a crystalline appearance, resembling galena. It was noticed during the tests that sulphidized charges which were set aside for a number of days before flotation often gave better results than the ones that were treated immediately after sulphidizing. Whether the artificial lead sulphide actually recrystallizes on standing is not known, but the results seem to indicate that it does.

Some of the most successful tests in the sulphidizing of lead carbonate ores followed by flotation of the artificial sulphide were with the normal (60 per cent") sodium sulphide of commerce.

DESCRIPTIONS OF TESTS AND RESULTS.

The results of a few tests of the most amenable ore tried are contained in Table 39. This ore was from the Shattuck mine, Bisbee, Ariz., where a large cave-in had opened up a considerable amount of it.

The table shows that 5 pounds of sodium sulphide per ton of ore was not enough for satisfactory extraction of the lead, but when 10 pounds was used per ton, applied in a per cent solution for two hours of contact, 93.2 per cent of the lead in the ore was recovered as concentrate containing 37.3 per cent lead. The use of larger amounts of sodium sulphide merely tended to increase the grade of the concentrate, the extraction of the lead and the silver not being greatly increased. The advisability of using more than 10 pounds of sodium sulphide per ton would depend upon local conditions and ore contracts. A long freight haul of the concentrates would probably make it advisable to use more sodium sulphide and to obtain highergrade concentrates. In each test the ore seemed to use all the sulphur in the sodium sulphide, but the solution was often alkaline after treatment, so that the excess of alkaline solution would have to be decanted before flotation and the thickened pulp thinned with fresh water. The reaction with the ore is probably according to one of the equations following:

PbCO,+Na,S+H2O=PbS+CO2+2NaOH=PbS+Na2CO2+H2O
2PbCO2+2NaSH=2PbS+2CO2+2NaOH=2PbS+Na2CO3+H,0.

The ore seems especially adapted to flotation, as the silver and gold in the ore accompany the lead and permit high extractions and good grades of concentrate. In fact, few present ore-dressing operations show an extraction of more than 90 per cent of the metal sought, as was obtained in the flotation tests of this ore.

Table 40 shows the results of sodium sulphide in sulphidizing two other lead-bearing materials that contained very little silver. One was material from the Scranton mine in the North Tintic district, Utah, and the other was tailings from the Wilbert dump near Arco, Idaho. From the Scranton ore more than 90 per cent of the lead was extracted in the form of a concentrate carrying 50 to 65 per cent lead. A mixture of coal-tar creosote and wood turpentine seemed to be a satisfactory flotation oil. Twelve pounds of sodium sulphide per ton of ore, applied in a weak solution for one-half hour, seemed to be satisfactory. The heading sample contained 9 per cent lead, or 180 pounds, which would require 68 pounds of sodium sulphide to convert the lead completely to sulphide, as only 12 pounds was consumed, all of the lead floated could not have existed as lead sulphide. Probably only the surfaces of the lead carbonate particles had been converted to sulphide of lead. This has been termed "sulphide filming." The Shattuck ore must have had an even thinner film of sulphide than the Scranton ore. More recent tests made by G. L. Allen, while in the employ of the Shattuck-Arizona Copper Co., have shown good extractions with as low as 2 pounds of sodium sulphide per ton of ore.

The Wilbert tailing was more difficult to treat successfully, as the extractions were usually low and the grade of concentrate rarely above 30 per cent lead. This tailing is from a concentrating mill and carries only 5.5 per cent lead.

Coal-tar creosote combined with wood turpentine, pine oil, or cedar oil made a suitable frothing agent for these materials.

Results of further tests with sulphide filming by means of sodium sulphide are shown in Tables 41 and 42. The material from the Bullion Beck slime dump illustrates one type of material that often resists all efforts to extract the lead efficiently by sulphide filming. Seemingly some compound or compounds in the material used up the sodium sulphide before it could blacken the particles of lead mineral. Usually an excess of the reagent would permit better extractions, but the consumption was too large for commercial work. Results of tests of some other materials of this kind are recorded in Table 43 (p. 104). Nearly all of these materials contained noteworthy proportions of colloidal alumina compounds or of colloidal limonite. The best results in sulphide filming with sodium sulphide were obtained with those materials that did not have such a large colloidal content.

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TABLE 39.-Results of sulphidizing ore from Shattuck mine with sodium sulphide. [Analysis of heading: Pb, 15.42 per cent; Ag, 12.88 ounces per ton; Au, 0.05 ounces per ton.]

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TABLE 40.-Results of sulphidizing ore from Scranton mine and material from Wilbert mill dump.

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Coal-tar creosote, 1.2, and refined turpentine, 0.2 pound.

1

"Creocedar," refined turpentine, coal-tar creosote, and rosin, 2 pounds.

MATERIAL FROM WILBERT MILL DUMP.

Per cent.

Per cent.

65.5

89.7

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500

500

10

500

10

500

20

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0.25

0.5

18

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31

Refined turpentine, 0.2, and crude coal-tar creosote, 1 pound..

33.15

79.4

Turpentine and S2C12, 0.8, and crude coal-tar creosote, 0.8 pounds..

27.2

57.2

a Consists of 3 parts of coal creosote to 1 part of cedar oil.

TABLE 41.-Results of sulphidizing material from Bullion Beck slime dump with sodium sulphide.

[Assay of heading: Pb, 5.5 per cent; Ag, 7.2 ounces per ton; Au, 0.02 ounce per ton.]

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