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The Bureau of Mines, in carrying out one of the provisions of its organic act—to disseminate information concerning investigations made-prints a limited free edition of each of its publications.

When this edition is exhausted copies may be obtained at cost price only through the Superintendent of Documents, Government Printing Office, Washington, D. C.

The Superintendent of Documents is not an oficial of the Bureau of Mines. His is an entirely separate office and he should be addressed:

SUPERINTENDENT OF DOCUMENTS,

Government Printing Office,

Washington, D. C. The general law under which publications are distributed prohibits the giving of more than one copy of a publication to one person. The price of this publication is 20 cents.

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CONTENTS

Introduction..

Scope of research work...

Problems in treating low-grade and complex lead ores.

Oxidized ores of lead...

Materials tested..

Mlethods of treatment..

Screen analyses of materials containing lead carbonate..

Leaching of lead from carbonate ores.

Preliminary tests.

Use of acidified brine for leaching..

First series of preliminary tests..

Second series of preliminary tests.

Third series of preliminary tests.

Tests of tailing from Wilbert dump..

Tests of material from Scranton mine.

Effect of sulphates in brines..

Preliminary tests.

Other tests..

Cyclic leaching......

Laboratory leaching tests.

Procedure and results.

Discussion of results of tests.

Conclusions from laboratory tests.

Large-scale cyclic leaching...

Plant used and method of operating.

Results of tests and discussion of results..

Puriiying the precipitate.

Precipitation with lime...

Precipitation on scrap iron...

Precipitation with sodium sulphide and hydrogen sulphide.

Precipitation with sodium carbonate..

Effect of using limestone.....

Tests to determine best conditions for maximum extraction..

Effect of volume of brine used..

Effect of heating the pulp....

Effect of adding chloride of lime..

Construction of plant......

Materials used in plant construction..

Character of sample tested....

Conclusions from results of tests..

Cyclic leaching and electrolytic precipitation

Roasting and leaching test at Salt Lake station..

Use of iron anode...

Tests at Bunker Hill and Sullivan plant.....

Leaching unroasted material with brine containing ferrie chloride.

Conclusions on leaching and electrolytic precipitation of lead..

Chemical reactions involved in brine leaching...

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