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converted into a chloridizing roasting by the introduction of a certain quantity of common salt into the furnace, which is found to obviate the difficulty. When the roasting is complete the ore is discharged from the furnace and allowed to cool. It is then damped with water to the proper degree (it should be only damped, not wet) and sifted into a large tub or vat —the chloridizing vat,—provided with a false bottom, on which rests a filter composed of broken quartz and sand The inside of this vat is covered with a coating of bitumen, or other impervious material not attacked by chlorine, in order to protect the wood. The vat is provided with a close fitting cover, which can be lured on and made air-tight . The ore being placed in the vat, chlorine gas is now generated in a leaden vessel by means of sulphuric acid, common salt and binoxide of manganese, and after being conducted through a vessel of water, in order to free it from chlorhydric acid, which, if allowed to pass into the ore, would produce a series of undesirable effects, is conveyed by a leaden pipe to the bottom of the vat. Here it gradually accumulates and rises through the ore. But as it is some time in reaching the top of the vat, the chlorine is generally admitted at the bottom, in order to save time, before all the ore is introduced, and the latter is then gradually sifted in as the chlorine rises.
When the vat is filled and the gas makes its appearance at the top of the ore, which may be known by its greenish-yellow color, as well as by its suffocating odor, the cover is placed over the vat and luted tight. The chlorine is still allowed to enter the vat until it begins to escape through a small hole in the cover, left open for the purpose. The supply of gas is then shut off, the hole in the cover stopped and hated, and the whole allowed to stand for twelve or eighteen hours, to complete the chlorodizing of the gold. Water is then introduced, which absorbs the chlorine and dissolves the chloride of gold formed. The solution is drawn off from the bottom of the vat, a small stream being permitted to run in constantly at the top till the lixiviation is complete. The residue in the chloridizing vat is then thrown away, while the solution obtained, which is precious, as it contains all the gold, is conducted to the precipitating vat or vats.
The chlorine gas employed in this operation is suffocating and poisonous if inhaled, and great care should be taken not to permit it to escape within the building. But there is little danger of sudden death from inhaling chlorine, since a few whiffs of this gas will serve as a sufficient admonition to greater caution.
To the solution of chloride of gold in the precipitating vats is now added a solution of protosulphate of iron, which precipitates the gold in the form of impalpably fine metallic powder. The solution is permitted to stand for some time, usually over night, in order to afford time for the precipitated gold to settle completely. The water is then carefully drawn off, the precipitated gold collected upon a large paper filter, carefully dried, and then melted and run into bars. The gold bars thus obtained, when the work is properly conducted, are . 999 fine. earth, or the reaching of the more deeply seated deposits with the smallest possible expenditure of time and money.
In practice, this process requires careful attention in all its various details, both in the roasting and in the subsequent chloridizing and precipitation of the gold. The presence of silver in any considerable proportion requires, moreover, important modifications of the process. But where only gold is present in the sulphurets, there is little difficulty —none but what can be readily managed by any one who has a fair comprehension of the general principles of the chemistry involved.
As stated, almost the only means yet adopted in California for pulverizing auriferous quartz, is the stamp, employed in the manner already described. Various other modes of crushing have been devised, but none of them have ever been extensively adopted, and it is difficult to foresee by what implement or mode the stamp is to be hereafter superseded, if any. In this connection it may be observed that the style of the California stamp and battery arrangement is in advance of that of any other country; while the means here employed in the best mills, to extract and save the gold, compares favorably with those anywhere in use. But many of the mills in California are still very imperfect in their gold saving appliances, the loss of the finer portions of the metal in the tailings being large.
In the treatment of sulphurets the same is true, though perhaps in a less marked degree; and it may be anticipated that the chlorination process, as it comes to be more widely known and better appreciated, will contribute largely to induce the employment of better and more systematic methods of concentration, the whole securing such economy in saving the precious metal, that a much lower grade of ore will soon be profitably worked than is practicable at present.
In view of the many novel experiments being made, and the new inventions seeking recognition by the mining public, it may be said that the employment of new modes and machinery promises, perhaps, less certain success than an adherence to the old, if only it be used with the requisite degree of intelligence and care.
The various gold washing implements and methods now in use do not by any means embrace all the styles and contrivances that have at different times marked the history of mining invention in California. The present perfection, as exhibited in these appliances and machines, was not reached, as some may suppose, by regular and direct advances from the use of the pan and batea to that of the cradle, tom, and sluice, culminating in the employment of the hydraulic apparatus and the cement mill, without any other modes having been meantime devised and tested. Many different plans were essayed, and scores of machines were invented and tried, to result almost wholly in failure and rejection; the period most prolific in these experiments being that which marked the transition from the use of the pan to the introduction of the hydraulic mode of washing. During its continuance a multitude of gold saving machines were invented and proved; some of them being costly, ingenious, and more or less serviceable, while a much larger proportion were not only useless, but absurdly defective, many wholly failing to separate the precious metal from the gravel and sand, while a few possessed the still less desirable property of saving the refuse and rejecting the gold.
For several years after the discovery of gold, the banks of the rivers, and even the roads leading to the mines, were lined with the remains of these crude and worthless machines; while in San Francisco the warehouses and wharves, and often even the vacant lots, were encumbered with them to a vexatious extent; their more speedy disappearance from these localities being due to the fact that the erection of forges and foundries created there an earlier demand for old iron.
To even enumerate, much less describe all these inventions, would now be impossible, there being scarcely a model of any of them left, while but few persons remain who could at this distant day accurately describe them in all their details. It may be said of them, however, in a general way, that they consisted of washers of almost every conceivable size, shape and material, involving in their workings every known principle of mechanics, and every movement recognised by dynamical science. Some were propelled by hand, and others by steam or water power. One variety employed riffles, and another sieves or screens as separators. Some were simple, and others complex; some large and ponderous, while others were reduced to the smallest compass, being easily portable in the hand. The effective principle in one kind consisted of a vibratory; in another of a centrifugal, or vertical action. In one case it was proposed to dredge the bottoms of the rivers with a series of endless buckets revolving on a cylinder, while again attempts were made to explore the deep still holes with sub-marine armor. Ingenious, eccentric and diversified, however, as were these contrivances, the fact that none of them ever attained to more than a temporary popularity—a few being too manifestly absurd to secure even a trial, sufficiently attests their general utility.
The sums of money spent upon these vagaries, during the earlier days of placer mining, amounted to millions of dollars, or their equivalent in time, a great deal of which was wasted in fruitless endeavors to render these new methods and machines available. And yet it cannot, perhaps, be said that this money was all foolishly spent, or this time vainly wasted. Aided by the lights of present experience, it is easy to detect the practical errors then committed, and to point out the fallacious theories entertained; but it should be remembered that little was known at that day in regard to the origin of placer gold, the agencies by which its deposits were formed, or even the places where it was most likely to make lodgment; while the business of seeking after and gathering it was wholly new to our people, very few of whom had ever seen even the simplest gold washing implement, or knew anything about the manner of using them.
All these were problems to be solved and things to be learned; and to the extent of that, these efforts were undertaken in the furtherance of these objects; they were entirely legitimate and even commendable. Many of these theories were, no doubt, chimerical enough, and the most of these inventions abundantly absurd: still as all this could only be verified by actual examination and trial, these endeavors, however abortive, fairly challenge not only respect, but sympathy and approval Though so generally disastrous to those undertaking them, and of little value in their immediate results, they undoubtedly formed a necessary part of that extended system of experiments from which the present highly effective means and modes of operating have been eliminated.
These disappointments and losses, though numerous and severe, were but the sacrifices usually exacted of every great industry at the outset—the crucial trials that many important interests in California, including those of quartz mining, manufacturing, and even farming, have been forced to go through; but which, like the pursuit we are considering, having survived these early trials, are now established on a permanent and prosperous basis.