Page:The American Cyclopædia (1879) Volume XV.djvu/61

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SILVER
53

into chloride or sulphate, the former by a chloridizing, the latter by an oxidizing roasting. The chloridizing roasting is essentially that of the Freiberg amalgamation process, and is effected by mixing salt with the charge. The silver chloride is extracted from the mass by lixiviation with hot brine (old Augustin process), cold brine (Hungarian improvement), sodium hyposulphite (Patera process), or calcium hyposulphite (Kiss process in Hungary and Russia, Hofmann in Mexico). The latter extracts also gold chloride if it is present, which brine will not do, unless it has been, as Patera recommends, impregnated with free chlorine gas. Experiments conducted at Wydotte, Mich., by Messrs. Courtis and Hahn, indicate the availability of other chlorides than common salt (particularly calcium chloride, or a solution obtained by treating common limestone with muriatic acid) as a solvent for the silver chloride. The novel and important results of these investigations are given in the “Transactions of the American Institute of Mining Engineers.” From its hyposulphite or chloride solution the silver is precipitated with metallic copper, as cement silver, which is washed, pressed, melted, and cast into bars. Ziervogel's method of extracting silver by roasting the sulphuretted ore to produce silver sulphate, leaching this with hot acidulated water, and precipitating with copper, is the simplest and cheapest of all; but it requires very skilful and delicate roasting, and ores comparatively free from lead, antimony, arsenic, and zinc. The three latter tend to cause volatilization of silver; the sulphide of antimony and lead cause a sintering of the roasting charge; copper dioxide, or too high a temperature in the furnace, leads to the formation of metallic silver, instead of the desired sulphate. Hence the application of this process is limited. Its best field is the treatment of the copper mattes of Mansfeld, containing 70 to 72 per cent. of copper, and 0.33 per cent. of silver. The so-called acid extraction is principally used upon cupriferous furnace products, which contain too much lead, antimony, arsenic, &c., to permit treatment by the Augustin or the Ziervogel method. In this process, the base metals are dissolved out by treatment with sulphuric or muriatic acid, and the residuum, containing gold and silver, is further reduced by smelting, or in rare instances by humid methods. For full discussions of all the foregoing processes, see Percy's “Metallurgy,” and Bruno Kerl's Metallhüttenkunde. The details of American practice, and critical comparisons of different American and foreign methods, are given in the reports of R. W. Raymond, United States commissioner of mining statistics, and in the “Transactions of the American Institute of Mining Engineers.”—The principal uses of silver have been mentioned already in this article; see also Coins, Galvanism (section on electrotyping), Mint, and Plated Ware. The real value of silver as compared to gold has varied in different ages from one eighth to less than one sixteenth; but the mint rates have often been arbitrarily established by government for the profit of the treasury, in spite of the market price of the metals. At present it is lower than at any previous period. The average ratio of value of silver to gold in the London market for the year ending Dec. 31, 1874, was 1 to 16.27. The following table shows the estimated product of silver at various periods in the present century:


COUNTRIES.  Estimate of 
J. Arthur
Phillips for
1800.
 Estimate of 
Birkmyre
for 1846.
 Estimate of 
J. Arthur
Phillips for
1850.
 Estimate of 
Birkmyre
for 1850.
Estimate of
 J. D. Whitney 
for 1854.
 Estimate of 
J. Arthur
Phillips for
1865.
 Estimate of 
W. P. Blake
for 1867.







Weight,
lbs. troy.
Value,
£ sterling.
Weight,
lbs. troy.
Value,
£ sterling.
Value,
U. S. coin.
Weight,
lbs. troy.
Value,
U. S. coin.








Russian empire 58,150  £167,831  60,00  £171,817  $928,000  58,000  $700,000 
Scandinavia
141,000 
32,346 
109,989 
  138,022 
 
198,200 
 
282,654 
 
7,444 
227,499 
20,400  35,607  328,000  15,000 
8,600,000 
Great Britain 48,500  160,000  1,120,000  60,500 
Hartz
Prussia
31,500 
21,200 
  138,022 
 
480,000 
480,000 
28,000 
68,000 
Saxony 63,600  198,200  960,000  80,000 
Other German states  2,500  48,000  2,500 
Austria 87,000  286,971  1,440,000  92,000 
France 5,000  80,000  18,000 
Italy 7,444  25,000 
Spain 125,000  440,210  2,000,000  110,000 
Australia
British America
10,000  128,000  9,500  20,000 
Chili 18,300  297,029  238,500  297,029  4,000,000  299,000 
10,000,000 
Bolivia 271,300  460,191  130,000  460,191  2,080,000  136,000 
Peru 401,850  1,000,583  303,150  1,000,583  4,800,000  299,000 
New Granada 5,000  42,929  13,000  42,929  208,000  15,000 
Brazil 1,200  2,003  675  2,227  11,200  1,500 
Mexico 1,440,500  3,457,020  1,650,000  5,383,333  28,000,000  1,700,000  19,000,000 
United States 1,864  17,400  73,532  352,000  1,000,000  15,500,000 
East Indies 56,265  56,265 
Africa 1,056  1,056 
Various other countries 33,000  33,000 







 Total 2,337,300  £6,515,925  2,827,425  £8,788,416  $47,443,200  4,017,000  $53,820,000 
Approximate value in U. S. coin   $36,250,000   $31,537,000   $43,853,000   $42,536,000  $47,443,300   $62,303,000  $53,820,000