Table showing the results of experiments upon Savage ore.

Actual value extracted. Value extracted per ton. Per cent. saved.

на стететастатст

Cents.
142.96 $82 52

Notes accompanying the experiments upon the Kentuck ore.

Nos. 1 to 20. Fifteen pounds of mercury added to the settler.
Nos. 21 to 23. Ten pounds of mercury added to the settler.

No. 3. No reason is known for the low yield both of gold and silver; the amalgam looked well and the fineness was very high.

Nos. 8, 9, 10. These charges gave a higher gold return than any of the assays of the ore. No sufficient explanation can be assigned for the fact. The assays of the bullion were carefully repeated with the same results. Charge No. 10 shows the greatest difference between the assay and the yield, in which case it is less than fourteen mills' worth of gold in excess of the amount assumed from the assay to be present. This excess may probably be accounted for by errors in the manipulation that the ore was subjected to during the treatment in the pan and settler. It is possible that the mercury when strained yielded a trifle more gold than usual. The fact is worthy of mention that all the charges that show an excess of gold, with the exception of No. 20, follow each other consecutively.

Nos. 17, 18. The sub-chloride of copper was added in a solution of salt. The quantity of copper was equivalent to the amount contained in one ounce of the sulphate of that metal.

No. 23. The quantity of copper corresponded to two ounces of the sulphate of the metal.

Notes accompanying the experiments upon the Savage ore.

Nos. 1 to 7. Fifteen pounds of mercury added to the settler.
Nos. 8 to 12. Ten pounds of mercury added to the settler.
No. 4. The pan by mistake ran six hours instead of five.

No. 5. No cause could be assigned for the low return of bullion.

Nos. 6, 7. The solution of sub-chloride of copper was the same as employed with Nos. 17 and 18 of the Kentuck ore.

Nos. 11, 12. The solution of sub-chloride of copper was the same as employed with No. 23 of the Kentuck ore.

It must be admitted that the results obtained in the above experiments are not, in all respects, satisfactory, nor do they point out conclusively the action and value of salt and sulphate of copper in the decomposition of the argentiferous ores by the Washoe process. They throw some light, however, upon several important points.

In considering the results, as shown in the tables, the most marked feature is the difference in the yield of the gold and silver bullion extracted from the two ores relative to the assay value. There is, with but one exception, in every trial of the Kentuck rock a higher yield than the requirements of the mines demand of the mills, and, in most cases, it is very much larger than is usually returned under the most favorable circumstances, in practical operation. This is probably owing, in a great measure, to the large amount of mercury employed in proportion to the quantity of ore. The Kentuck also gave as favorable results where mercury alone was used as when chemical agents were added. This proves very decidedly the ability of quicksilver, aided by heat and iron, to decompose the purer and easily reducible argentiferous minerals. With the Savage ore it may be observed that the yield is in all cases not only very much below that from the Kentuck, but lower than the average returns from the mills upon ores that are not first subjected to a roasting process. This is undoubtedly due to the large percentage of blende and galena present, with which the precious metals are in combination. The use of chemical agents shows a decided improvement in the production of bullion from such ores as contain large quantities of base metals. The application of salt and sulphate of copper did not increase the loss of mercury, although in many charges large quantities were present in the pulp. In the experiments con ducted, with every possible precaution to repeat the precise conditions of a charge, using the same quantities of salt, sulphate of copper, and mercury, the results differ as widely as in those cases where the amount of chemical agents employed are much less, or entirely abandoned. The cause of these great differences in the yield of bullion must be sought elsewhere than in the varying amounts of the chemical agents used, however important they may be, in certain cases, in aiding and assisting decomposition. A favorable yield undoubtedly depends more upon the native condition of the mercury than anything that is usually added to the pulp. Charges 8, 9, 10, 11, of the Savage table, ran only four hours, which may in some degree account for the low yield. Charge 12 ran five hours with a somewhat higher result. It should be stated that the mercury of charges 11 and 12 appeared to contain a small amount of lead, which may have rendered it partially inactive. Charges 21, 22, and 23, of the Kentuck table, were discharged at the end of four hours, without any marked decrease in the production of bullion. It seems probable that in the case of the latter the minerals are all easily reduced, and the amalgamation is practically accomplished in the allotted space of time. In the case of the Savage ore the base metals are but slightly attacked

by the mercury, and require more time for any chemical changes before amalgamation can take place. There is considerable resemblance between Nos. 3 and 4 of the Savage table, with a large excess of salt and sulphate of copper, and Nos. 6 and 7 with a solution of the sub-chloride of copper. The reason may be found in the fact that in the former the chloride of copper formed would be quickly reduced by the iron to the state of the sub-chloride, and similar conditions produced as in the case of the latter.

Chemistry of the process.-The action and value of common salt and sulphate of copper in the amalgamation of argentiferous ores, by what is known as the patio process, has always been a somewhat disputed question. Numerous theories have been advanced by metallurgists of long practical experience in Mexico, to account for the reduction of the sulphide of silver by the methods adopted in that country. The two which have obtained the most prominence, and which chemists have received with most favor, differ very widely in the manner the decomposition is supposed to be accomplished. The most plausible theory, and the one now generally adopted, is that of Sonnenschmidt. He claims that the salt and sulphate of copper react upon each other, and produce sulphate of soda, which is neutral in its action, and chloride of copper. This fatter salt then acts upon the argentiferous sulphide, and yields chloride of silver, subchloride of copper, and free sulphur. The sub-chloride reduces a second portion of the sulphide of silver, and causes the formation of an additional amount of the silver chloride, and sub-sulphide of copper. The silver salt is then attacked by the mercury; calomel, or sub-chloride of mercury, is produced, while metallic silver is set free, which combines with a second portion of the mercury, as amalgam. The following chemical equations show the reactions:

NaCl+CuOSO = NaOSO,+CuCl

2 CuCl + AgS=AgCl + CuCl + S
Cu Cl+AgS= AgCl + Cu2 S
AgCl + Hg=AgHg+Hg,Cl.

Bowring, an English metallurgist, on the other hand, denies that any of the sulphide of silver is chloridized, and asserts that before amalgamation takes place, metallic silver is first produced. He claims that chloride of copper, in contact with mercury, forms the sub-chloride of both metals. The sub-chloride of copper, in contact with the oxygen of air, is converted into an oxychloride, which, in turn, acts upon the sulphide of silver, and liberates the metal in a free state, by oxydizing the combined sulphur. These reactions are expressed as follows:

2 CuCl+2Hg=Cu,Cl+Hg C1
Cu,C1+0=CuCl CuO

3 (CuCl CuO) +AgS=Ag+SO3+3 Cu2Cl.

Although oxychloride of copper may possibly be found at times, there does not appear to be any decided evidence that such is the case in practical operations, or that it decomposes the sulphide of silver, while the experiments already recorded show conclusively that both the chlorides of copper, under favorable circumstances, do chloridize the argentiferous sulphurets. The experiments, however, would seem to indicate that the action of the chloride of copper was much more intense than that of the subchloride.*

* Mr. Bowring's very ingenions arguments may be found in Ure's Dictionary of Arts, etc., vol. iii, p. 664. London, 1867. He urges the following considerations against the theory of the formation of chloride of silver and its decomposition by mercury in the patio:

1. Ores containing silver combined with chlorine only, are considered by Mexican miners most difficult of reduction, causing thrice the loss of mercury, and rendering the process much more tedious than those containing sulphides only. The amalgams from chloride ores and from sulphide ores are very different in appearance. The chlorides instantly attack the quicksilver, coating its globules with calomel-whereas sulphides leave it bright, proving, as Mr. Bowring claims, that they are not transformed into chlorides of silver during the process, and then decomposed by the mercury.

2. It is true that a strong solution of the chloride of copper, mixed with a solution of salt, and placed in contact with sulphide of silver, will, after some time, form chloride of silver and sulphide of copper; but the amount of sulphate of copper introduced in the patio process being sometimes less than one ounce and never more than eight ounces, to 70 pounds of water, could not give a sufficiently concentrated solution to permit this reaction.

3. An inspection of the formulæ given in the text shows that, on one hypothesis, sulphur is set free, and on the other, (Bowring's,) sulphuric acid is formed. That the lat ter is really the case, Mr. Bowring claims on the strength of the following experiment: Rich ore, containing sulphide of silver, is mixed with oxychloride of copper in a solution of common salt, and mercury is added at ordinary temperature. In about an hour the whole of the silver will have become amalgamated, when, after separating all the

The application and modification of the amalgamation process, as practiced in Washoe, has occasioned among experienced mill-men great doubt as to the beneficial results derived from the use of any chemical agents at present mixed with the ore. This doubt is occasioned, or at least strengthened, by the growing custom of late years of decreasing the quantity of salt and sulphate of copper added to the charge without apparently diminishing the product of bullion. Many amalgamators now abstain from the use of both reagents; others add a small quantity of the sulphate of copper, but no salt. In a few instances, the custom is to throw in only a little of the latter, while in many mills the rule is to employ a small amount of both substances, owing to a slight prejudice against the abandonment of "chemicals" altogether.

The action exerted by these two reagents in the pan would appear clearly to indicate that the benefits derived from their use are partly to aid in converting the sulphide into chloride of silver, as in the patio, and partly to decompose such minerals as are but slightly attacked by the mercury. In the Washoe process, however, the large quantity of iron present must tend greatly to produce sub-chloride of copper almost as soon as the chemical agents are thrown into the pulp.

Notwithstanding the importance of common salt and sulphate of copper in the patio, and, under certain conditions, in the pan, their value must be considered as only secondary in the decomposition of a large proportion of the Comstock ores. The advantages derived from their use are shown to be exerted chiefly upon such minerals as blende and galena, which are but slightly attacked by the mercury. But the amounts employed are in most cases too small to effect any very favorable results. On the other haud, if a sufficiently large proportion of the reagents are consumed in the pulp, in order to produce the beneficial returns, it is always at the expense of preserving the necessary purity of the mercury. The quantity of salt deemed necessary by mill-men varies from one-quarter of a pound up to seven or eight pounds per ton. Scarcely any two establishments have the same rule. Its action upon the ore, without sulphate of copper, in producing any marked results may well be doubted. The consumption of the sulphate of copper also depends upon the ideas of the amalgamators, but the amounts do not differ so widely as in the case of the chloride of sodium. It ranges from one-quarter of a pound to three pounds per ton.

The addition of the sulphate without salt is, of late years, a common practice. The opinion among those who work their ore in this way is, that it gives a little better yield than when mercury alone is employed, particularly where the ore indicates the presence of galena in any considerable amount, in which case it is said to quicken the mercury, and render it more energetic. Continued experience appears to determine this fact with a considerable degree of certainty. In working ores containing only a small percentage of lead, the quicksilver very soon becomes dull and inactive, or, as it is technically termed, it sickens, and the yield from the pan is consequently low. Lead is one of the most deleterious metals in destroying the amalgamating energy of mercury, and at the same time is very rapidly absorbed when the two metals are brought into contact. Sulphate of copper possesses, to a certain extent, the property of expelling lead from mercury, copper being amalgamated and sulphate of lead formed at the expense of the sulphuric acid of the copper salt. If a concentrated solution of sulphate of copper be allowed to stand upon lead-amalgam the action takes place quite rapidly, mercury containing lead acting much more energetically upon the copper solution than when perfectly pure. This salt, however, does not appear, under any circumstances, to possess the power of completely driving out the lead. Another advantage derived from the addition of a small quantity of the sulphate of copper is that mercury, under certain conditions, when exposed to the solution, forms a minute amount of copper-amalgam, which causes the metal to act with a somewhat greater intensity in the decomposition of the silver sulphide than when perfectly pure. Iron, as a reducing agent, in the pan process, probably plays an important part in bringing about the favorable results obtained. This may occur in three ways: First, it aids, in a great measure, the decomposition of the chloride of silver; secondly, it reduces the calomel formed during the operation; the chlorine, combining with the iron, goes into solution, and the heavy metal is liberated. In this way it not only prevents a chemical loss of mercury but also serves to keep the surface of that metal bright and clean, which otherwise might be coated with a thin film of sub-chloride, which would greatly destroy its activity; thirdly, it undoubtedly assists directly in the amalgamasoluble salts by filtration, a test with chloride of barium precipitates sulphate of baryta equivalent in quantity to the sulphur which has become acidified.

Whatever may be the case in the patio process, it seems to me that Bowring's theory does not agree with the facts of the pan process. In this case, the ores of chloride of silver are considered the easiest of reduction; and the best method hitherto discovered for the treatment of refractory ores involves their chlorination preparatory to amalgamation. But the notion that the pan reactions are the same as those of the patio, though quite common, is not necessarily true. One great difference is in the amount of exposure to the air, and this alone would be sufficient to account for the presence of oxychloride of copper in the patio and not in the pan.-R. W. R.