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It has been found necessary to roast ores containing organic matter in the crucible before adding the zinc, otherwise the final solution will be too dark to titrate. It was also occasionally found that in cases where there was no organic or carbonaceous matter in the ore, that the solution was very dark; and it was found, after a number of experiments, that this blackening came from the decomposition of the carbonic acid from the combustion of the gas. This has been obviated by making a thick coating of very fine zinc, or by a cover of pulverized borax glass, which fuses, and protects the mixture beneath from the action of the products of combustion of the gas.

The following results have been obtained from this process:

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In a Brown Hematite.

By zinc method, . . 48.63, 48.72, 48.71, 48.74, 48.83, 48.69 per cent.; mean, 48.72 By reduction by hydrogen (after previous oxidation with oxygen gas) at a red heat, 48.74 per cent.

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The use of pulverized zinc of somewhat coarser grain is very advantageous in the reduction of iron to the ferrous condition in solution. Any one who has used granulated or plate zinc knows of the trouble often experienced in effecting complete reduction and in dissolving the last traces of the zinc. The large surface exposed by the granulated zinc insures complete reduction in a short time, and the small size of the grain is a guarantee that its final solution will not be tedious. The practice is to add to the ferric solution, in a flask, 5 grams of 40-mesh zinc. There should be but a very small excess of sulphuric acid, so that at the end of an hour or two only about half of the zinc will be dissolved. Then more sulphuric acid is added, and the solution quickly boiled, and the process conducted as above.

I have tried the "blue powder" from zinc works as a substitute for the pulverized zinc, but the results are not, as a rule, as satisfactory. I have found the pulverized zinc useful in treatment of sulphurets to render them soluble in hydrochloric acid, and I have other experiments in progress in the treatment of ores and minerals. is probable, too, that other metals in finely divided form, as iron. reduced by hydrogen, may have uses in analytical chemistry.

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A MINING LABORATORY.

BY ROBERT H. RICHARDS, PROFESSOR OF MINING, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, BOSTON.

(Read at the Wilkes-Barre Meeting, May, 1877.)

THE Institute of Mining Engineers has shown so much interest in the educational problem of profitably combining theory and practice, that it seems especially appropriate to lay before its members the methods and aims of the mining laboratory of which I have charge, and in which one form of combination of hand with head work is now being tried. If anything may be contributed toward the solution of this problem by the discussion which follows, my purpose will be attained.

Whether it was wise or not to establish a mining school so far from the principal mining centres, does not now enter into the question. Given, a mining school already begun, how shall it be made most efficient in developing engineers who are trained to think for themselves as well as versed in the works of others? This is the question with which we have had to deal.

In considering the bearing of this laboratory work upon the students' preparation, it will be convenient to take it up under five different heads:

1. The methods and aims of the laboratory.

2. The advantage to students of having a part, at least, of their practical work in the curriculum of their school.

3. The advantage to be derived by mines and works.

4. Degree of accuracy which may be attained in working ores on a small scale.

5. Results of work in the laboratory.

1. The Methods and Aims of the Laboratory.-During the May meeting of 1873, held in Boston, I had the privilege of reading before you a paper stating the plans and aims of this laboratory. Since that time we have been constantly following out those plans, and are more than ever convinced that we are working in the right direction. We do not feel that the time we have spent has been in any sense thrown away. Perhaps the aims of the laboratory can be most clearly shown by illustration. Many young engineers leave school thinking that they know everything. They go to the works, and expect to teach the superintendent something and the men a good deal, regardless of the fact that it is this spirit that has prejudiced workmen against schoolmen. They are often more trouble than they

are worth for a considerable period of time. They have simply learned metallurgical processes from books, but they have not derived from them a realizing sense of the meaning of the word economy, nor do they understand how to carry it out in actual practice. They are too apt not to perceive that the profit of works lies in the little savings in material, in labor, in time and power, etc., and that the differencé between making these little savings and in not making them is almost always the difference between profit and loss, or between success and failure. In fact, our young engineers are not, as a rule, fully enough aware of the fact that failures in mines and works are quite as often the result of errors in judgment as they are from poverty of the deposit or process.

The aim of this laboratory is to correct this state of things, and to turn out men who have learned somewhat of the value of economy; who have found out by their own experience that little losses, taking place here and there and everywhere in their work, mount up enormously in their final account of stock.

For the sake of example, we will suppose that a silver-lead ore is given to a student who is entirely inexperienced in such matters, and who is inclined to be self-sufficient. On reading up, he finds that such ores, when worked on the large scale, are subject to a loss, which we will say is 15 per cent. of the silver, and which takes place largely in the smelting. He is surprised at this, and thinks it is a large loss, and expects to do as well or better. On taking account of stock, however, we will suppose he finds his losses are: silver in dust while crushing and handling, 2 per cent.; roasting, 15 per cent.; agglomerating, 3 per cent.; smelting, 15 per cent.; fume in refining, 2 per cent.; handling in refining, 6 per cent.; fume in cupelling, 4 per cent.; parting and recovering, 3 per cent.; total, 50 per cent.

He is astonished to find that his total loss amounts to 50 per cent., and that by carelessness in handling alone, he has lost 11 per cent., the whole of which might have been obviated as well as not; that in roasting he used too high a heat, and in cupelling the same; that by having large condensing flues, he might have saved a large proportion of the loss in smelting and refining.

In fact, this man has either learned a lesson in the economy of metal working that will last him his life, or he has failed to learn it. In either case, whatever may be the risk incurred by a works in taking an untried man from a school, the risk is in some degree lessened by this test of the man. We believe that ability to offer to works a selection of men is all the incentive we need for developing

this laboratory. We hold that the school owes a duty to the works as well as to the student, and that the supplying of works with good men is fully as important a duty of the school as the finding of places for the student.

The methods of working the laboratory will best be given by a brief description of the last year's work. The course began in February with a class of thirteen students. The work was allotted so that each student had the entire responsibility of a whole process or of a part of a process.

A quantity of low grade ore from the Merrimac Mine, weighing 44 tons, was treated first.

Two students, A and B, took charge of the mineral examination, and of the crushing and washing. They were assisted in the washing by their whole class, who had this opportunity to operate the washers, and to make themselves familiar with the principles on which they work. The class came on, five men at a shift, and they worked ten shifts of four hours each; in this way every man had an opportunity to work and to study every machine.

The captains, A. and B., meantime took charge on the alternate shifts, so that one of them was always on hand to keep watch, and to see that waste did not take place, that samples were taken at the proper intervals, and that everything went on as it should. When the work was through, they dried, weighed, sampled, and assayed all the final products. They found out then whether the refuse was poor enough to throw away. They found out which machine did the greatest work, and which the least. In fact, they were in condition to report upon the economy of the process from beginning to end. They afterward made numerous tests on sands falling into water, and speculated on possible alterations which would be desirable if the washers were to be used exclusively for the ore in question. These tests were rendered possible by means of a series of samples which had been taken at every stage of the process. A, reported especially upon the crushing machines and the washing jigs, while B, reported upon the spitzkasten and on the tables which were used in washing.

Three products were the result of this treatment:

1. Smelting ore. 2. Middle-grade ore. 3. Refuse.

C. and D. took charge of the smelting ore; this was first roasted in reverberatory furnaces. The whole class came on by shifts of four hours each, and the operation went on night and day continuously until finished. The total time required was 52 hours. C. and D. then agglomerated the ore, sampled it, analyzed it, and

also their fluxes (limestone, tap cinder, magnetic iron ore, etc). They planned their smelting to obtain a given slag, matte, and metal. When it was smelted in the shaft furnace all the class came on by shifts, and by means of this run, and several others during the term, every man was able to serve in every place, and thus to learn the principles which underlie the whole operation, as well as the details by which it is carried on in the laboratory. This smelting yielded1. Lead. 2. Matte. 3. Slag.

C. followed up the metal, and turned out silver, lead, and gold. D. followed up the matte, and turned out copper, lead, and silver. Their reports consist of a detail of the operations, results of analyses, and tables showing where, when, and how the losses took place, with suggestions as to how they would mitigate them another time.

E. and F. undertook to work the middle-grade ore, and they tried the Ziervogle, Augustin, Von Patera, as well as roast, chlorination with amalgamation, and a number of other methods. They divided the processes, one taking the responsibility of a part, the other of the rest. They report moderate success in some and dead failures in others.

A sulphuretted ore was allotted to G. and H. This ore, as a matter of course, required to be first roasted. We have two methods of roasting, by reverberatory furnace and by kiln. But as a kiln had never been tried in the laboratory, and as it was to a certain extent doubtful whether it could be made to work, a division was made. G. took the kiln roasting, followed by the subsequent smelting, roasting and smelting, etc., while H. took the method by reverberatory furnace, followed by the subsequent processes. This work was carried on in the same spirit as before indicated.

K. took up nickel, looked up the published methods, and experimented upon its extraction.

L. worked a gold ore by Atwood's amalgamators, concentration, and gas chlorination. This method is still in its experimental condition with us.

M. had a barrel of quartz galena assigned to him.

N. had a barrel of silver ore assigned him, which was to be treated by pan amalgamation.

O. worked out a problem on a copper ore from a mine at Santa Fe. The question to be settled was whether it would pay best to turn out a slag lean in copper, and at the same time a poor copper pig, or to turn out a pure copper pig, and at the same time allow some metal to enter the slag. His results are very interesting.

VOL. VI.-33

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