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Show MINING REVIEW. INTER-MOUNTA- IN The Chemical Assay. BY II. IIIRSCIIING. In the last issue of the Mining Review I note an article upon the chemical assay, by Mr. James W. Neill. He seems to overlook that we are living in the age of general scientific progress, and that men of knowledge are no longer arrested and prosecuted on that account. If he advocates such dealings with progressive men, he was evidently born in the wrong age. No one has a right to cast stones at the progressive metallurgist and chemist, for these are the men to whom all progress of recent years in the line of natural sciences is due and certainly they will replace the old time assayer, notwithstanding Mr. Neills proposition. The article in question does not require any detailed comment on my part. It claims that the cyanide process is the only one worth consideration, and yet the results are usually lower from 10 to 30 per cent than the fire assay. The author evidently has no knowledge of Prof. A. Classens Gold and silver estimation, or Prof. Plattners Chlorination process, or of the volumetric silver estimation, which is used in every United States mint and first-claassay office in this country on account of its accuracy. Such processes are recognized by men of learning and to classify them with bunko sharps would be an injustice. If he refers to any particular swindlers, he should name them and expose them. I desire to call attention to a series of articles recently published by the American Institute of Mining Engineers, discussing fire assaying, combination assaying and analytical methods, wherein the accuracy of the and crucible assaying Is plainly shown up. The fact cannot be disputed, as it comes from the highest authority of the United States. They are proposing to the smelters and miners to change the entire system of fire assaying in such a manner that justice will be done to the miner, and they ask to introduce other and better methods for determining gold and silver than the methods which are now used. It is known to every advanced scholar that no progress is made in fire assaying and the methods are today the same as the ancient miners used centuries ago. I remember the time very well, when copper was determined by fire assaying, and today we would call an assayer who estimates copper by fire assaying an ignoramus. The time is near at hand when the assayers will have to adopt the progressive ideas of the scientists. It cannot be denied, however, that for common and crude wrork the fire assay has its advantage, but, on the other hand, it must be admitted that It is not correct and not accurate, and the sooner other methods are substituted the better for the mining interests at large. This is not an age in which ane cient and methods should be advocated as superior to modern methods. and any such effort will be emphatically condemned by progressive ss and sold on the fire assay is misleading. deposited in the form of a mass of The question fs how much can be ex- nearly pure brimstone. From the outset the company operattracted of the precious and other metals from ores by a suitable process, in ing this process seemed doomed to disorder to make a property pay. Men aster; they were advised to erect the who have sometimes bought and sold plant near Indian Trait station, N. C., mines on the fire assay only, and as it in order to take advantage of the large exis done occasionally by quantities of sulphureted and base gold perts, have been very often fooled; evi- ores said to be obtainable in the neighborhood, but which proved to be an ildence of it can be found everywhere. In regard to the analytical methods lusion. Then, great difficulty was enused by some assayers, I must admit countered in obtaining such large cruthat they are indeed very unsatisfac- cibles capable of withstanding the extory in every respect and if anybody pansion of the heated ore, and in this wants to criticise, there is a field for it. they never really succeeded. The furIn my opinion the labor and chemicals nace was erected, fired before the segthe crucibles were conspent are simply wasted. No practical ments of nor theoretical benefit can be derived structed were set, and at the first heat from it, and for what reasan the ore all burst, so discouraging the owners, buyers demand such results is a mys- who had expended close to $100,000, tery. More knowledge is needed and that they threw the plant up in disgust. so-call- ed w-hic- everyone who works and experiments on better extraction processes should be encouraged. Desulphurization by Electricity. A correspondent of the Engineering and Mining Journal gives the details of the practical working of Dr. Henry Eamess process for the extraction sulphur from pyrites and of sulphuret gold ores, as follows: About 1888 Dr. Eames discovered that the passage of an electric current through pyrites heated to redness In a closed vessel not only effected the separation of the sulphur, but left the resulting roast in perfect condition for pulverization and amalgamation of the gold contained. After long experimenting on a laboratory scale in Baltimore, a large plant was erected in North Carolina, which closely followed in form the original apparatus. It consisted of a circular mass of brickwork containing a large firebox for burning wood, the flames of which passed up into a chamber in which were set six vertical pots or retorts, holding each about one ton of broken rock. The bottoms of the retorts swung downward, and were pierced with a number h holes for the exit of the of sulphur, and in turn this perforated bottom was connected and luted to an iron receiver running on wheels to facilitate handling. A thick soapstone cap fitted the mouth of each of the retorts which were flush with the Iron platform constituting the top of the crucible oven; through the caps passed two cast-iro- n rods one foot apart and reaching within a few inches of the bottom, forming terminals connected with the two poles of a dynamo, and As soon as the properly insulated. furnace was sufficiently heated, a charge of ore broken to about one and a half inches was introduced and carefully packed round the terminals, the top luted on, the poles connected with the dynamo, the contents brought to a red heat and was allowed to remain there for about eight hours. It was found that until the fumes of sulphur began to appear at the test hole no current passed, but then a circuit was immediately formed and continued till all the sulphur was expelled, when the circuit was broken and the distillation men. completed. Upon opening the receiver The assertion that mines are bought about 90 per cent of the sulphur was sco-rifieati- old-tim- 5 on one-inc- Their engineer, however, finding two of the crucibles in fair condition, patched them up, and for a year ran them successfully, grinding the roasted ore in a Huntington mill, and selling the brimstone or sealing fruit jars, etc., at a good price. At this point I was asked to look into the matter, and succeeded in putting through two charges in the now much dilapidated crucibles, one of which burst early in the heat, the other when . nearly completed. I obtained considerable brimstone, but not the theoretical quantity, owing, I believe, to the cracks in the crucible. There appears to be no doubt as to the action of the electric current in accelerating the distillation, and I think, with a properly constructed furnace, two charges could readily be run in twenty-fou- r hours, but I should recommend retorts of not more than twelve cubic feet capacity. As my trial was made rather to demonstrate the claim that the roasted ore amalgamated freely than to save the sulphur, I did not take the pains I might otherwise have done to repair the furnace and crucibles, and I believe the owners have done no further work. One of the gold ores I experimented with contained 25 per cent of iron, principally magnetite, but the roast was nearly perfect and the gold quite free. So far as I could ascertain, the cost of roasting sulphureted ores did not exceed $2 per ton, and with cheap fuel on sufficiently large scale might be considerably reduced. 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