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Improved Processes of Extracting Copper from Its OresWilliam W. CulverState University of New York at Plattsburgh



Hunt & Douglas Copper Process

• What is it?

First commercial “wet” process for low-grade

copper. Patented 1869 in USA, 1870 in Chile.

• Why is it important?Memory - reminds “us” of the deep roots of

chemical extraction of metals, and pioneering

efforts in Chile to process low-grade copper.

• How did I come to study it?

Good question.



Selection from Patent Paragraph 2

“For the extraction of copper ores by this process it is necessary that it should be in

the state of protoxide [CuO], or suboxide

[Cu2O], or some compound of these oxides…

The pulverized and naturally or artificially

oxidized ore are then digested with a watery

solution of protosalt of iron , with or without

the addition of an earthy or alkaline

chloride. We prefer the neutral

protochloride of iron [FeCl 2 ]… By the action

of a solution of protochloride of iron [FeCl 2 ]

on the oxides of copper [CuO & Cu2O] these

are converted into dichloride of copper

[CuCl 2 ], which is readily soluble in

concentrated solutions of earthy or alkaline

chlorides – such as common salt [NaCl]. At

the same time the iron separates from the

solution as an insoluble oxychloride [FeOCl].”

[bracketed modern formulae are added]

Paragraph 2



The Chemistry 1869 Hunt in Scientific Paper

• First stage reactions:

Cu2O + FeCl =

Cu2Cl + FeO

• Second stage reactions:Cu2Cl + 3FeO =

Cu2 + FeCl + Fe2O3

• Final Result:

3Cu2O + 2FeCl =2Cu2Cl + 2Cu + Fe2O3

(Errors for cuprous chloride & ferrous chloride

traced back to atomic weight errors.)

1953 Van Arsdale Hydrometallurgy

• Molecular Formula

CuO + FeCl2 + H2O →

CuCl2 + Fe(OH)2

• Balanced Equation

3Cu2+O2-(s) + 2Fe2+Cl2-(aq) + 3H2O →

2CuCl (aq) + Cu2+Cl2-(aq) +

Fe(OH)3(aq)



Context of the Terminology

• Vat leaching method based on chlorine’s observed

high reactivity & strong oxidizing capacity.

•

1860s discovery of elements – chemistry’s frontier.• Mendeleev’s periodic table published 1869.

• Determination of atomic weights debated.

•

Isotopes unknown (atomic weight confusion).• Ions unknown.

• As issues were clarified, language evolved.



Table 1: Published Atomic Weights

with the Hunt & Douglas Process

E l e m e n t 1840

Graham

1858

Fownes

1858

Cannizzaro

1869

Medeleev

1876

Hunt &

Douglas

Modern

Cu 31.71 31.7 63 63.4 31.75 63.55

Fe 27.18 28 ---- 56 28 55.85

Cl 35.47 35.5 35.5 35.5 35.5 35.45

O 8.01 8 16 16 8 16



Table 2: Formula and Terminology

Comparison Chart Modern

Molecula

r/Ionic

Formulas

Hunt &

Douglas

(1876)

Formula

Hunt &

Douglas

(1869) Patent

Hunt (1869)

Scientific

Copper

Article

Other Hunt

& Douglas

(1869)

Terminology

Hunt & Douglas

(1876)

Promotional

Booklet

Modern

Latin

System

Names

Modern

Stock System

Names

Cu2O/

Cu2+O2

Cu2O oxides of

copper/red

cuprous oxyd suboxide dinoxyd of

copper

cuprous

oxide

copper (I)

oxide

CuO/

Cu2+O2-

Cu2O2 oxides of

copper/black

oxidum

cuprosum

protoxide protoxyd of

copper

cupric oxide copper (II)

oxide

CuCl/

Cu+Cl-Cu2Cl cuprous

chlorid

protochlorid of

copper

cuprous

chloride

copper (I)

chloride

CuCl2/

Cu2+Cl2-

dichloride of

copper

cupric chlorid dichloride of

copper

FeCl2/

Fe2+Cl2-

FeCl protochloride

of iron

ferrous

chlorid

iron

dichloride

protochloride of

iron

ferrous

chloride

iron (II)

chloride

FeO/

Fe2+O2-

FeO ferrous oxyd ferrous oxyd hydrated ferrous

oxide

ferrous

oxide

iron (II) oxide

Fe2

O3

/

Fe22+O3

2-

F2

O3

ferric oxyd ferric oxyd ferric oxide iron (III)

oxide

FeOCl/

Fe3+O2-Cl-iron

oxychloride

oxychloride

of iron

iron (III)

oxychloride

NaCl/

Na+Cl-

chlorid of

sodium

chlorid of

sodium

common salt chlorid of

sodium

sodium

chloride

sodium

chloride



Who Were the Patent Holders?

James Douglas T. Sterry Hunt



Their Careers

Douglas CV• Born 1837 Quebec City, Canada

• Education: University of Edinburgh &

Queen’s College, Kingston, Canada

• Degree in theology, with some studies of

medicine (chemistry) at Laval University

• 1864 took charge of family investment atHarvey Hill Copper Mine as high-grade

ore exhausted (bornite)

• 1867 tested Whelpley & Storer Process

• 1869 patented copper process with Hunt

• 1871 consulting in Chile nine months

• 1875 Chemical Copper Corporation

• 1880 Phelps Dodge & Arizona

• Published some 300 articles, 5 books

• Died 1918 New York City

Hunt CV• Born 1826 Norwich, Connecticut

• Education: Yale University with B. Silliman

• Geological Survey of Canada 1846-72

• Laval University, Prof. Chemistry 1856-62

• McGill University, Prof. Chemistry

• MIT, Prof. geology 1872-78

• Patents with Douglas 1869-1892

• Published 6 scientific books

• Published 346 scientific articles

• Member & officer of most USA, Canadian

& European scientific societies• Questioned “atom theory” in favor of

continuous matter

• Died: 1892 New York City



Hunt & Douglas Process Plants

• Harvey Hill Mine, St-Jacques de Leeds, Quebec1869-75.

• Compañia de Minas de la Invernada, Tiltil

1870-75.• Ore Knob Mining Company, 1873-75.

• Sociedad Minera de Andacollo, 1870-?

•

Chemical Copper Co., Phoenixville, Penn. 1875-80.• Stewart Smelter, Georgetown, Colorado, 1874-80.

• Kansas City Smelting & Refining, 1895-97.



Harvey Hill Mine 1860



Compañia de Minas de la Invernada

• Chile had venture capital.

• Investors with a correct

diagnosis of the looming

crisis in Chile.

• Copper investors

assuming great risk to

move the industry and

the country ahead.

• Chile lagged in science &

engineering to keep at it.

• “Para que V.E. pueda juzgar mejor

del valor del procedimiento y los

grandes ventajas que va a reportar al

país dice, que existen grandes

cantidades del desmontes de cobre

de 4 a 5% en Chile que hasta ahorase han considerado de ningún valor,

también hay cerros inmensos de

minerales de baja ley que

actualmente nadie esplota por no

conocer un método barato de

beneficiar." -Juan Stewart Jackson, President,

Compañia de Minas de la Invernada, to

Pres. José Joaquín Pérez, 1871



Ore Knob, North Carolina, USAwater, ore, solution

Leaching tanks

Precipitation

tanks

Solution

recovery

Roasting

furnace



Chemical Copper Company 1876

Leaching Tank

House



Chemical Copper Company

• Five years custom ore processing allowed for

continual experimentation with varied ores.

•

Developed hydrometallurgy as basis for acustom smelter.

• First copper electrolysis in North America.

• Where Douglas developed his skill as a

metallurgist.

• Bankrupt after a second furnace house fire.



Problems and Subsequent PatentsYear Patent # Name

Patentee

Title of Patent

(solvent/product)

Extraction

Method

1869 86.754 H & D Improvement in Processes of Extracting Copper from Its Ores

(protochloride of iron & common salt /cuprous chloride)

iron precipitate

1874 151,763 D, H, S Improvement in Extracting Silver, Gold, and Other Metals from

Their Ores

(protochloride of iron & common salt/chloride of copper )

iron precipitate

1880 227,902 H & D Extracting Copper from Ores

(chloride & sulphurous acid/dichloride of copper)

iron precipitation

or filter

1887 364,174 H & D Process of Extracting Copper from Its Ores

(ferrous chloride & common salt/cuprous & cupric chloride)

iron precipitation

or filter

1893 506,985 D Methods of Separating and Recovering Copper

(chloride of iron & sulphurous acid/sub-chloride of copper)

iron precipitation

or filter

1896 563,144 D Process of Extracting Copper from Ores(“chlorid” salt & sulphurous-acid gas/cuprous chloride)

Electrolysis

1900 664,537 D Process of Extracting Copper

(chlorid/cuprous chloride)

Electrolysis



Hydrotechnology

• Hydrometallurgy vs. Hydrotechnology.

• Shared idea – place ground ore in a solution in

order to manipulate desired metal.• Leach.

• Precipitate.

•

Electrolysis.• Float off top.



Reflections

• Low-grade metal mining is on defensive today.

• Low-grade metal mining is humanity’s way ahead.

•Considering historical perspectives is one way tomaintain dialogue.

• Hydrometallurgists have a burden to be creative in

solving known problems.

• Investors take a risk, but must balance return with

safety for workers and the environment.



Conclusions

•

The Hunt & Douglas Copper Process “worked.”• It is an early instance of scientific insight leading

to business opportunity.

• Ahead were decades perfecting the necessary

engineering and methods:

-non-selective mining,

-overall mine/plant scale of operation,

-particle sizing and sorting.• Blind alleys and dead-ends helped find the way

ahead for overcoming the low-grade challenge.

william culver

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