Hoke:Refining-Page-Index

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TABLE OF CONTENTS

Contents

Modern introduction to the book

Read this before reading Hoke! It deals with new knowledge since 1940.
Introduction to Hoke - REFINING PRECIOUS METAL WASTES by FrugalRefiner and others.

I.THE PURPOSE OF THE BOOK

What the book does.
What it does not do.
Is a knowledge of chemistry essential?
How to use the book.

II. MATERIALS TO BE DISCUSSED

Jewelers' wastes.
Dental wastes.
Photographers' wastes.
Base metals present in precious metal wastes.
Non-metallic admixtures.
Old electroplating and stripping solutions.
Economics of refining the various kinds of wastes.

III. THE SIMPLEST CASE-PLATINUM FILINGS THAT CONTAIN NO GOLD

Platinum without gold
Equipment and chemicals used.
"Acquaintance experiments."
Beginning work; sieve; magnet; caustic; heat.
The nitric acid treatment.
How to fold a filter paper.
Summary.
Questions and answers.

IV. ARRANGEMENT OF EQUIPMENT. DISPOSING OF FUMES

Planning your workspace
Materials for hoods.
Lighting.
Burners.
Fans.
Water and plumbing.
Storage of chemicals.
Hazards.

V. THE COMMONEST CASE GOLD SCRAP THAT CONTAINS NO PLATINUM METALS

Basic gold refining methods
The first refining.
Equipment and chemicals.
Acquaintance experiments.
Beginning work.
(1) Preliminary treatments.
(2) Melting into a button if desired.
(3) Treatment with nitric acid.
(4) Dissolving gold in aqua regia.
(5) Removing excess nitric acid.
(6) Recovering the dissolved gold with copperas.
(7) Washing the fine gold.
(8) Melting the fine gold.
(9) Saving the silver.
Old filter papers.
What to do if you spill acids or caustic.

VI. MORE ABOUT GOLD - ALTERNATIVE METHODS

More gold refining methods
(I) Alternative preliminary treatments.
(2) Melting the material into a button. Quartation.
(3) Removing base metals with acids.
(4) Dissolving the gold in aqua regia.
(5) Evaporating off the excess nitric acid.
(6) Recovering the dissolved gold by alternative methods: sulphur dioxide; oxalic acid; sodium nitrite; metallic precipitants --copper, iron, zinc.
(7) Washing and
(8) Melting the fine gold.
(9) Saving the silver.
Summary.
Questions and answers.

VII. SOME SPECIAL CASES

Special gold cases
Green gold.
White golds.
Rolled, filled and electroplated gold, and gold scrap containing soft solder.
Procedure when tin and lead are present.

VIII. SILVER

Silver refining
Forms of silver encountered by the refiner.
Its characteristics and properties; acquaintance experiments.
Metallic wastes-scrap, filings.
Non-metallic wastes.
Silver chloride and its conversion into metal.
Silver in solution: the nitrate; the sulphate; stripping and pickling solutions.
Cyanide solutions of silver or gold, including plating baths.
Mirror solutions.
Photographers' wastes.

IX. IDENTIFYING METALS IN SOLUTION

Testing metals in solutions
The need for identification.
Definition of "in solution".
Equipment for making tests.
Testing for gold in acid solution.
In alkaline or cyanide solution.
Testing for silver.
Stannous chloride solution for all precious metals.
Standard solutions of gold, platinum, palladium.
Using stannous chloride with platinum; with gold; with palladium; with silver.
Usefulness of stannous chloride.
If the tests are inconclusive.
Two or more precious metals.
Dimethyl glyoxime for palladium.
DMG and nickel.
Other chemical tests - The glow test.
Copper.
Iron.
Acids and alkalies-litmus paper.
Other tests.
A warning.
Identifying metals in solid form.

X. GETTING ACQUAINTED WITH THE PLATINUM GROUP

Platinum group acquaintance experiments
The six metals and their employment in art and industry.
Books to read.
Familiar chemical characteristics.
Platinum and ammonium chloride.
Palladium and ammonium chloride.
Palladium and acids.
Possible experiments.
A little about iridium.
Questions and answers.

XI. JEWELERS FILINGS AND CLIPPINGS CONTAINING MIXTURES OF GOLD AND PLATINUM

Jewelers filings
Kind of materials.
Equipment and chemicals.
(1) General cleaning.
(2) Removing base metals.
(3) Removing gold.
(4) Removing silver chloride.
(5) Melting the platinum.
(6) Recovering dissolved platinum.
(7) Burning the orange powder and melting the sponge.
(8) Melting the platinum sponge.
(9) Recovering the gold from the aqua regia solution.
(10) Washing and melting the fine gold - The stock pot.
(11) The Silver Jar.
Summary.
Questions and answers.

XII. ALLOYS AND BUTTONS CONTAINING GOLD AND PLATINUM GROUP METALS

Gold and pgm alloys
Materials handled.
Jewelers' buttons.
Dental alloys.
Equipment and chemicals.
(A) Preliminary treatments.
(B) Melting into a button if necessary.
(C) Granulating the button or rolling it thin.
(D) Dissolving the metal in aqua regia.
(E) Recovering the iridium from the silver chloride.
(F) Recovering dissolved platinum.
(G) Recovering dissolved gold.
(H) Recovering silver if worth while.
(I) The Stock Pot.
Summary.
Diagram.
Silver rich buttons.
Questions and answers.

XIII. THE STOCKPOT

Stockpot
Materials handled.
Equipment and chemicals.
Collecting the precious metals with zinc.
Refining the black powder.
The iridium residue.
The dilute aqua regia solution,-platinum, palladium, gold.
Burning the red palladium powder.
Further treatment after palladium has been removed.
Disposal of the final tailings.
Diagram.
Questions and answers.

XIV. ALTERNATIVE METHODS FOR CHAPTERS XI , XII, AND XIII

Alternative methods
Part I-An alternative procedure for the aqua regia solution in Chapter XI or Chapter XII.
Part II-Formic acid method of reducing the colored powders.
Part III-An alternative method of precipitating palladium, using dimethyl glyoxime.
Part IV-Alternative methods of refining the Stock Pot.
Diagram for the second scheme for Stock Pot concentrates.
Questions and answers.

XV. REPURIFICATION OF GOLD, PLATINUM, PALLADIUM, SILVER, IRIDIUM

Repurification
Part I. Repurifying gold: by reprecipitation; the use of oxalic acid; by fire; by chlorine gas; by electrolysis.
Part II. Repurifying platinum.
Part III. Repurifying palladium: the colored powders; buttons or bars; palladium black; palladium sponge.
Part IV. Silver.
Part V. Iridium.

XVI. SOME MORE SPECIAL CASES

Special cases
Sand, glass, porcelain and enamel.
Emery and carborundum.
Chromium plate.
The peculiar case of 18-k green gold with platinum;
stripping with the current; equipment; the current;
recovering gold and silver from cathode and cyanide bath.
Mercury and amalgams.
Dental pins.
Gold pen points with osmiridium tips.
Gold leaf.
Contact points.
Chemical ware.

XVII. RHODIUM, RUTHENIUM, OSMIUM

Rhodium ruthenium and osmium
Their rarity.
Rhodium.
Ruthenium.
Osmium.
Refining the "mysterious" metals.
Some schemes of separation: ( I ) The classic system.
(2) The method of Gilchrist and Wichers.
A list of books and papers referring to the three rarer metals.

XVIII. LOW GRADE WASTES

Low grade wastes
Materials discussed.
Determining the method of disposal.
Two extreme cases.
Part I. The shop of moderate size.
Procedure for floor sweeps.
Equipment for dressing floor sweeps.
Procedure for wash-barrel residues.
For old crucibles.
Flue dust.
Paper storage.
Polishings, grindings, old aprons, floors, etc.
Old solutions.
Fluxes for use with low grade wastes.
Litharge. Lead buttons.
Cupellation.
If platinum is the only precious metal.
Part II. The large plant.
Amalgamation not profitable.
Disposal of the final fine dust.
Sampling.
Refining of the final sifted dust.
Questions and answers.

XIX. LOSSES

Handling losses
Metal losses in the refining room.
Metal losses in the shop.
Metal losses in the furnace room.
How much loss is permissible?
Figures on losses in melting gold.
On losses in melting and reworking platinum.
On losses in polishing.
Losses due to dishonesty.
Losses of money, rather than metal, due to mismanagement.
Difficulty of estimating the value of wastes.
Assaying.
Questions and answers.

XX. MORE ABOUT EQUIPMENT

Refining equipment
Where to buy equipment.
How to order.
When handling large quantities.
The Büchner funnel.
New ideas in chemical apparatus.
More about ventilation.
Crucibles.
Cleanliness in the refinery.
Wash-barrels and filter-presses.
The Cottrell precipitator.

XXI. PROCESSES USED BY THE PROFESSIONAL REFINERS

Large scale refining
Materials handled.
Virgin metals.
By-product metals.
Secondary metals.
The Miller chlorine process.
The various electrolytic methods.
Possible variations.
Advantages and disadvantages of the electrolytic methods.
Can professional methods be adapted to small-scale operation?

XXII. SOME LARGE PROFESSIONAL REFINERIES

Some Large Scale Refineries
The Irvington Smelting and Refining Works.
The Miller process at the Homestake Mine.
The Raritan Copper Works.
The United States Assay Office.
The plant at Acton, England.
Some other large plants: Copper Cliff; Montreal East; Old Hickory; The Royal Mint at Ottawa, Canada.

APPENDIX A. MELTING THE PRECIOUS METALS

Melting
Part I, Platinum and its group.
Fuel and equipment.
Melting small lots of platinum scrap.
Working and annealing.
Melting platinum filings.
Defective platinum.
Platinum sponge and black.
Large melts.
Making up platinum alloys.
The electric furnace.
The oxygen torch.
Spectacles.
Crucibles and refractories: lime; zirconia; sand; contamination from the crucible; other refractories.
The platinum group and occluded gases.
Melting and working palladium.
Melting the other platinum metals.
Part II, Melting gold and silver.
Sources of information.
Melting the fine gold powder.
Melting lemel.
Melting clean scrap.
Deoxidizers.
Fluxes.
Casting precious metals.
Making up new alloys.
New light on old metals.

APPENDIX B. HAZARDS

Safety
The National Safety Council.
Comparison of chemical and heat burns.
First aid.
Chemical eye burns.
Neutralizers.
Alkalies and caustics.
Hydrochloric or sulphuric acid.
Hydrofluoric acid.
Nitric acid.
Nitrous fumes.
When handling sulphuric acid.
Shower baths.
Cyanide poisoning.
Mercury.
Hazards of the melting room: hazardous arrangement; crucibles; oxygen cylinders.
Stains on the skin.
Gas masks.
Some articles to read.

APPENDIX C. LAWS AND REGULATIONS

Legals
Federal licenses for handling gold.
Regulations concerning Government purchase of precious metals.
National Stamping Law covering gold, silver, and their alloys.
Law for stamping platinum.
The Commercial Standards.
Local ordinances.
Standards in foreign countries.

APPENDIX D. A LIST OF DEALERS

Buyers of precious metals.

APPENDIX E. BOOKS TO READ

Books to read.

INDEX

Alphabetical index
           ACIDS, to remove from skin ... By-product metals
           CADMIUM ... Eldorado Gold Mines, Ltd.
           Electrolytic methods ... Henrich, H., Inc.
           Henry, Peter, & Son ... Mercury, to recover
           Merrill Co. ... Platinum, defective
           Platinum, melting point of ... Silver, to melt
           Silver, to recover from cyanide solution ... Von Bernewitz, M. W.
           WAGOR, Elry J. ... ZINC, to reduce silver salts
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