Search Documents

By A. F. Taggart, Nathaniel Arbiter

The chemical reaction occurring in collection of nonmetallic minerals with amine-type collectors was early postulated by students of flotation phenomena to be metathesis between the mineral and the collector, involving exchange between the amine-bearing (aminium) ion and the cation of the mineral, and formation at the mineral surface of an oriented film of the amine salt of the mineral anion. Qualitative evidence of exchange has been obtained on several occasions at Columbia. Thus 1000 C.C. of a solution containing 495 mg of laurylamine hydrochloride was shaken 17 min. with 100 grams of barite and ground in a porcelain mill to pass a 200-mesh screen; the mixture was then set aside for 48 hr. Filtrate therefrom analyzed 476 mg. per liter of laurylamine hydrochloride. There was no substantial loss of chloride ion (78.4 mg. per liter in the original; 74 in the filtrate). No successful analyses were concluded for barium ion. Earlier, confessedly rough work with scheelite indicated a solution gain in Ca++ equivalent to about one-half the aminium ion lost. Real quantitative roof of the exchange, in the form of an established stoichiometric balance, is unknown to the authors. The data of the present paper, however, obtained from experiments designed on the basis of the exchange hypothesis, constitute strong evidence of its truth, and at the same time point the way to economic utilization of the expensive nitrogen-bearing collectors in concentration of the low-priced nonmetallic minerals. The basic postulate underlying the experiments performed was that, if the collecting reaction is of the type R+ + Y- + MX = RX + M+ + Y- where R = aminium ion, Y = the anion of the amine salt, and M and X are, respectively, the cation and anion of the mineral, the reaction should obey qualitatively the implications of the mass-action and solubility-product laws. This is to say that coating and collection should be aided by the addition to the solution of either ion (R+ or X-) of the collector-coating compound, and hindered by the addition of either of the ions M+ or y-. Experimental work comprised determination of (,) the relative solubilities of the laurylammonium salts of a variety of nonmetallic-mineral anions; and (21 the contact angles' of various minerals in solutions containing different concentrations of the postulated controlling ions. Semiquantitative flotation tests were run With barite as checks on the diagnostic character of the contact angles. The amine

Jan 1, 1947

By C. F. Willis

The time is no longer when a man can act as an independent unit; the appreciation of the interdependence of one man upon another has emphasized the importance of the social unit. Epidemics have made us recognize that even a man's health is not distinctly his own to control as he pleases. The physical examination of workmen previous to employment started with an effort to prevent the spread of tuberculosis, for tuberculosis may be detected in its early stages and cured. But it was soon found that many other diseases were detected and the saving of lives made possible. The physical examination does not mean the elimination of the unfit—on that basis it would utterly fail—but rather the measuring of a man's physical fitness and placing the man where he can do the best for himself, his fellow worker, and the company. Industry as a whole cannot expect to live up to the standard of physical examination set for the army, nor should it expect to do so, for in all branches of industry there are types of work that do not require the same amount of endurance as does army work, and the lacing of men with physical limitations in the work for which they are capable permits a higher average of physical fitness for the work requiring physical excellence. Objects of Physical Examination The objects of physical examination are: The early detection of illness, particularly at a time when a full restoration of health is possible; the protection of employees from infection caused by working in contact with contagious diseases; the discovery of a man's physical limitations, in so far as his possibility for rendering good service is concerned; assistance to the safety movement by eliminating association in hazardous occupations with men whose physical condition renders them likely to accident to themselves and others; and the lessening of time lost by sickness. Statistics issued by the United States Department of Labor show that 22.54 per cent. of idleness is caused by sickness, with an average number of 7.71 weeks idle; whereas only 1.66 per cent. is caused by acci-

Jan 1, 1920

W. D. BRENNAN,* Cheyenne, Wyo. (written discussion?).-My experience has been that, where possible, it is preferable for each foreman to employ his own men, rather than to have them handled through an employment bureau. The fact that each foreman comes into direct contact with the man before he is put to work gives him an opportunity to choose, at certain times, the kind and class of men that he wishes. Where possible, after a man is employed he is sent to a central office where a complete history of each individual is kept on a card. If a man has previously been in the employ of the Company, his history can be obtained from this card, and if for any reason he is not wanted he can be refused work at the time he reports to, the central office. In connection with Workman's Compensation costs, we in Wyoming feel that although the rates of compensation paid may in some cases be rather low our law works satisfactorily. As the State and the number of employees are small, compensation cases are handled through Judges of the various District Courts. In the State Treasurer's Department, a few clerks were added to look after the handling and issuing of warrants and compiling of statistics. Most of the large employers have an arrangement by which a joint claim and assent, specifying the amount of compensation due, is made tip by the employer and signed by the workman. This is forwarded, to the Judges so that personal investigation of individual cases is not necessary. In this manner, compensation is promptly received and' overhead expenses of operation of the law is kept at the minimum. The law requires each employer to pay into the State Treasury, for the benefit of the industrial fund, a sum equal to 1.5 per cent. of the money earned by each employee, engaged during each calendar month of such employment. Each employer contributes monthly, unless the sum heretofore contributed, after deducting all payments made on account of injuries to his employees, shall equal a full 1.5 per cent. of his annual pay roll, computed by multiplying his current monthly pay roll by twelve, and shall likewise be not less than ($5000). It has been found during the years that this law has been in effect, that a number of the larger employers have been exempt from payment for from five to eight months per year, so that in some cases, even in coal nines, industrial insurance has cost less than 0.75 per cent.

Jan 3, 1919

GEORGE F. COMSTOCK (author's reply to discussion*).-Mr. Thum's description of the effects of butt welding and spot welding on the micro-structure of steel are interesting and timely. The speed with which the changes noted by Mr. Thum must take place is indeed remarkable, but the writer has noted a similar very rapid diffusion of carbide in annealing a t a rather high temperature certain samples of soft sheet steel containing massive cementite segregated on a small scale. The massive cementite in such steel can be dissolved and distributed very quickly if the proper temperature is attained. Mr. Thum's explanation of the structure he found in the spot welds seems entirely reasonable, but the mystery of the decarburized material in the butt weld is one that might well be the subject of further research. The possibility of decarburization by air ,might perhaps be worthy of a little more consideration than he gives it, for the oxides formed would be gaseous on account of the presence of carbon, and hence not visible in the microscope, and the effect of the pressure might be to squeeze the carbon oxides, which would normally form blow-holes, out of the metal or possibly into such small volumes as not to be noticed The removal of carbon by liquation and squeezing into the fin would be an effect similar to the "bleeding" of a steel ingot that is rolled while the center is still liquid, giving a soft low-carbon interior in the finished section while the segregate was removed in cropping the pipe. This effect in Mr. Thum's butt welds could, however, only be obtained if the weld was heated to near the melting point of the steel, and if the carbon was considerably segregated in the bars at the start, for the first effect of the high temperature would be to promote diffusion rather than the contrary segregation and Equation. It is gratifying to learn from Dr. Ruder's remarks that his researches have resulted in no disagreement with the few points brought out by the writer's experiments. In addition to the three forms in which nitrogen may occur in iron that he mentions, it would seem that a fourth form is often found; This is apparently a eutectoid, like pearlite, and sometimes almost as coarse as the massive cementite seen in soft steel sheets that have been annealed for a long time. One of the things needed in the metallographic study of steel is an etching reagent that will distinguish definitely between nitride in this form and the more common pearlite or cementite.

Jan 6, 1919

I AM sure, that you understand that of all the things created by the most high God Himself or by Nature at His command, not one-even though it be an atom or the smallest worm-has been produced without some particular gift. And if we do not always discern this in every thing, the cause lies in our defective vision, in our little knowledge, and in our lack of careful thought concerning the necessity of seeking hidden things. Certainly those things that have such inner powers, like herbs, fruits, roots, animals, precious stones, metals, or other stones, can be understood only through oft-repeated experience. [37] Others do not need so much knowledge and belief for their, powers are obvious and shown to us at all times by their effects. They reveal themselves to us through the sense of sight by their splendor and variety of colors, through the sense of smell by their odors, through the sense of hearing by the melody of the harmonious or unpleasantly discordant repercussions. of the air. They likewise manifest themselves by. their softness or harshness. As you see, all those things, according to. their limits, are conveyed .by the ordinary senses to the mind, by whose distinctions all their species, both harmful and beneficial, are discerned. Then they are reviewed by the judgment in all their degrees of perfection and imperfection, so that whoever seeks them with careful study or with experience often finds them. Now, in order to shorten this discourse, since I wished to speak to you of lodestone and its properties, I tell you that it is one of those things that show their apparent effects to our sight by a particular virtue hidden in such a way that its cause, as far as I know, has never been known to the very wise natural speculators who have spoken on every other subject. Thus one who considers its actions carefully must surely marvel, for it appears that Nature has put into this stone a certain spirit of vivacity, so that it seems to have-I would like to say-hands, although they are not seen. For I see that it not only attracts iron but also takes hold of it and keeps it attached to itself. This action is certainly great enough to bear certain witness to the virtues possessed by other created things that do not manifest their powers to the external senses. In order not to prolong this discussion, I tell you the following. This stone is found in various places and of different colors and properties. The

Jan 1, 1942

By Milnor Roberts

CORNWALL, a Mecca for metal miners the world over, is easily reached from the southern coast of England. Passengers who land at Plymouth or Southampton can connect with a fast train from London called the "Riviera express," which traverses the beautiful counties bordering the English Channel. In Cornwall the traveler soon notices the pits and stock-piles of white china clay, and the metal mines, both placer and hard rock. The deposits are associated with granite batholiths, of which there are four principal ones, each a few miles in diameter. Tin mines are especially worked in the granite near its borders and also in the immediately surrounding Paleozoic slates. Copper and lead are no longer of importance here but tin is being produced steadily from several mines, with arsenic and tungsten as by-products. At the close of the war the man-power available. for these mines had been reduced to one-third of normal, and only now is it again reaching full strength. As mining in Cornwall antedates the Christian era, even a Nevada prospector would have to admit that "she's a permanent camp." SUB-TROPICAL CORNWALL Redruth and Camborne are industrial centers of the tin mining industry, but more tourist hotels are found in neighboring resorts such as St. Ives, a quaint fish-ing town on the Atlantic-side of the peninsula of Corn-wall, where the numerous cats descended from those mentioned in the ancient riddle-rhyme about St. Ives now occupy every doorstep and wall. Another charm-ing resort. Penzance on the shore of the English Channel, is known by name to the public through the opera "The Pirates of Penzance," but is of especial in-terest to students of nature for its palm trees and other subtropical plants, which thrive owing to the nearness of the gulf stream, although the latitude is that of northern Newfoundland, Winnipeg, and the northern end of Vancouver Island. Among the industrial plants at Camborne are those of Holman Brothers, Ltd., where drills and other forms of mining equipment are manufactured. At the Corn-wall School of Mines, which specializes on the district, the staff has assembled excellent collections of local ores, which repay study by a visitor.

Jan 1, 1928

By C. R. Johnson, R. A. Greenkorn, G. W. Widner

This paper describes a short, simple well-testing procedure evolved from unsteady-state concepts to appraise wellbore damage in water-input wells. Input rates are changed at specific intervals over a 30-minute period and the wellhead pressure recorded at the end of each interval. From these data, the pressure drop due to the "skin" can be computed. This pressure drop in terms of psi/B/D of input rate is referred to as the "skin factor". Two of these variable-rate tests are required to determine change of wellbore damage and to evaluate well-treatment techniques. There are several advantages to the variable-rate procedure. The necessary data can be obtained with wellhead gauges and meters. There is little interference with normal operations. The short testing period eliminates many interpretative difficulties that come from interference from adjacent wells. The shut-in period required for standard tests before the plot of pressure vs log of time attains a straight line is often 12 hours or more. Such a time period is incronvenient, especially when a well must be tested repeatedly to evaluate change in wellbore characteristics. This variable-rate procedure has been successfully npplied to water-input wells in three fields. For some of the wells, skin factors were calculated from both the standard and the variable-rate tests. These results show good agreement. THEORY OF THE VARIABLE-RATE PROCEDURE In many waterflood input wells, the pressure in the wellbore differs from the pressure in the reservoir immediately adjacent to the well because of the restriction of flow through the skin of the well. If the true pressure of the reservoir at the well, p,, is that pressure which would exist in the well if no skin were present, and p,' is the actual pressure as measured in the well, this difference, is the skin effect. Fig. 1 shows the change in skin effect with change in flow rate. As the flow is reduced, the skin effect is reduced by an amount equal to the change in wellbore pressure minus the change in reservoir pressure. The equation of pressure change without skin using the point-source solution of the diffusivity equation is (after van Everdingen')

By Paul Hunt

UP TO June, 1923, the Park-Utah mine had shipped about 94,000 tons of a direct-smelting ore of a gross value of $4,200,000, or about $45. a ton. These values were in gold and silver only, although the ore carried small amounts of lead, copper and zinc. Freight, treatment and deductions had averaged $15.40 a ton. At the expiration of the Pittman Silver Act there was in sight about 30,000 tons of a similar ore with a gross value of about $15 a ton in gold and silver, and a large body of partly developed lead-zinc ore of a gross value of about $20 a ton, 40 per cent. of which was represented by the lead-zinc content and the balance by the silver and gold. Mine costs had been high during the life of the Pittman Act, but as a large part of the profits had gone into equipment of the mine and the orebodies were large and had good walls, we knew that mine costs could be greatly reduced. We were therefore faced by the necessity of getting lower freight and smelter rates or of concentrating the ore. We did obtain better freight rates on lower grade ore, and a favorable smelting rate on the small tonnage of siliceous silver-gold ore, but this smelter rate could not be applied to the lead-zinc ore with any profit to ourselves. The Judge mill of the Park City Mining & Smelting Co., with which we were affiliated, was running to capacity; if we built our own mill it meant a 5-mile freight haul to a satisfactory millsite and a year's delay. Fortunately, the International Smelting Co. had just inherited a mill at Tooele which, with some changes, was about double the capacity required for its own ores. Flotation tests were run on Park-Utah ore and a contract entered into with a low base treatment charge per ton, the tariff being largely fixed by the metallurgical deductions. This contract has been admirably calculated so that the miner can follow a lean orebody to its limit. Such a procedure has no doubt made it difficult for the smelting company at times, but it has resulted in finding ore extensions that otherwise might have been missed, so in the long run it has profited too. A flat rate per ton would have been like mining up to the claim endlines in a great many of the stopes. In order to offer such a contract it can be inferred that the smelting company must have been able to make high recoveries and high-grade products on a very lean ore.

Jan 1, 1928

By E. T. Dumble

Discussion of the paper of E. T. DUMBLE, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 104, August, 1915, pp. .1623 to 1638. E. L. DEGOLYER, Norman, Okla. (communIcatIon to the Secretary*).-Referring to Mr. Dumble's description of the stratigraphy of eastern Mexico, I should like to question the classification of the ?Papagallos? or ?Mendez? shales as being of Cretaceous age and the so-called overlapping of the Papagallos or Mendez shales by the Alazan shales; the classification of the San Felipe series as Cretaceous, and the correlation of the San Felipe series with the San Juan limestones. Mr. Durable apparently recognizes the continuity of the great shale formation by his use of the terms "Papagallos" and "Mendez," as equivalent and interchangeable, since the Papagallos Hills in the State of Nuevo Leon and Mendez Station in Northern Vera Cruz, localities at which the shale formation outcrops, and from which the formation names are taken, are approximately 250 miles apart and on opposite sides of the Tamaulipas barrier. The Papagallos shales (evidently referring here to the northern extension only) are said to be non-fossiliferous and no reason for .their Cretaceous classification is given, though in a previous article' they are classified as Cretaceous because at their northernmost outcrop they "have the same relation toward the overlying Tertiary that the Escondido (Cretaceous) has through its whole extent." The Alazan fossil locality was found by me and the first collections from it were sent to Dr. Dall; about 17 species of marine invertebrates were recognized by him, the fauna noted as having a distinct Pacific tincture, and the age of the formation from which they cause pronounced lower Eocene. The outcrop of the shale formation has been traced continuously from this point by me and my assistants into the Panuco River region, where Eocene fossils are reported at a depth of 1,810 ft. in a well at Topila.2 From Topila the formation has been traced continuously north to the Padilla-Jiminez region in Central Tamaulipas. Lithologically, the formation is fairly constant and though I am only generally acquainted with it north of the Padilla-Jiminez region, until definite evidence of the Cretaceous age of the Papagallos shale in its type localities, or of an overlap, is available, it seems to me more logical to consider the shale formation a single stratigraphic unit of Eocene age.

Jan 12, 1915

By C. E. Arnold

In attacking the problems of mining and treating large disseminated copper orebodies such as those occurring in the Miami or the Ray district of Arizona, one of the vital questions to be decided is, "What is the value of the orebody per ton in place?" The importance of this question lies in the fact that its answer helps to reach a decision concerning the method of mining to be employed. Let it be assumed for the moment that milling and smelting practice, especially the latter, is more or less standardized, and has a cost incapable of much variation, while the cost of mining has a considerable range owing to the large number of mining methods by which a mine may be exploited. For instance, a method may be adopted whereby all the available ore can be extracted perfectly clean (i.e., unmixed with barren material) at a relatively high cost; or a method may be used involving the necessary dilution of a portion of the ore with waste, in order to recover that portion, thus giving a relatively poorer extraction but nevertheless a lower working cost than the former method. Naturally, between these two extremes there lie intermediate methods. In order to arrive at a solution of a mining method problem that is of any value, it is necessary that accurate and complete estimates of mining, milling, and smelting performances and costs shall be established. By way of illustration is given a case of mining, by the system of undercutting and caving, a large orebody with an average content of 1.50 per cent. copper supposedly all in sulphide form, to which case has been applied those results in mining operations which one may fairly assume are to be expected when viewed in the light of G. R. Lehman's ore-drawing experiments, which form the subject of a paper to be presented at this meeting. It is assumed that the total costs will be as shown in the table on page 204. To attain these costs, a daily production and treatment of 14,400 tons has been assumed. Other assumptions are as follows: 15 per cent. of orebody is to be extracted clean by development work and undercutting; 63.8 per cent. (75 per cent. of 85 per cent.) is to be extracted clean by caving, leaving 21.2 per cent. part of which is to be extracted by diluting with waste, and the remainder lost. Dilution and extraction are to

Jan 1, 1917

By Rossiter W. Raymond

I DESIRE to call the attention of the Institute to a novel system of dredging, which, it seems to me, may prove applicable, not only to river and harbor improvements, but also to certain varieties at least of alluvial and diluvial gold mining; that is, river-mining, barmining, coast-mining, and any other similar operations now carried on by means of coffer-dams or dredging machines. The simple and effective method to which I refer is the invention of General Roy Stone, formerly an officer of volunteers, and at present a civil engineer, engaged under General Newton, of the United States Engineer Corps, upon the government works in New York harbor. General Stone has been, since September, 1878, in charge of operations upon Diamond Reef. This reef, lying between Governor's Island and the Battery, is one of the most dangerous in the harbor. Its position in the highway of navigation, and the fact that it is dangerous only to vessels of considerable draught and at certain stages of the tide, combine to increase the serious nature of the disasters which it has caused. The reef consists partly of rock in place, and partly of deposits of glacial clay, boulders, and pebbles, over all of which lies, or did lie until it was removed, the ordinary silt and rubbish of the harbor. As the purpose of the present paper has nothing to do with the special dimensions and other circumstances of this particular work, I describe those features only which are connected with General Stone's ingenious device. Various attempts have been made to remove the upper portion of Diamond Reef and secure a navigable depth at low tide. Some years ago Maillefert undertook to accomplish this by firing charges of high explosives, simply laid upon the surface. He accomplished some good in the removal of projecting points and ridges ; but as soon as the surface of the reef had become approximately level, his method was no longer effective. After the work had been taken up by the Engineer Corps, the well-known drilling-scow invented by General Newton was brought into action ; and, so long as holes could be bored and fired in solid rock, this process was effective enough. In the mixture of hard-pan

Jan 1, 1880

By John A. Church

In the year 1874, when the price of pig-iron was still high, that staple product became the subject of discussion in the newspapers and among those philosophers who are determined to know the "reason why" for all things. The object of the inquiry was to find out Why iron did not fall in price as much as some other things had fallen. Indeed, there seemed to be an impression that iron and gold ought to move on nearly parallel lines, for the fact was constantly brought forward that iron then cost twice as much as it did before the war, though gold had returned to within twelve or fifteen per cent. of its former value. After some time the papers, by what seemed to be nearly unanimous consent, reached the conclusion that the maintenance of high prices was the work of the furnace proprietors, who, as the result of their shrewdness, were pocketing enormous profits. No proof was given to support this opinion, and the figures of cost and sale that were produced were of the most general kind, and used in the most vague manner. Visiting the president of the Thomas Iron Company, whose great works at Hokendaqua and Catasauqua, in Pennsylvania, are so well known as the largest and among the best conducted in America, I found him quite willing to meet the vague suspicions of the newspaper wiseacres, by a publication of the figures contained in the furnace-books of his company. These were accordingly given to the world through the Engineering and Mining Journal, and attracted the general attention they so well deserve. Though my own name became connected with these statistics, from the fact that I used them as the basis for the first attempt ever made to calcalate the furnace economy of an American works, I can, without the suspicion of egotism, say that the statistics referred to are the most valuable contribution the literature of American blast-furnace work has yet received, for their interest is independent of personal considerations, and due entirely to the fact that they represent faithfully the details of practice in one of the most prominent American works. They are an exact transcript of the furnace-books, and form a body of accurate information of the greatest value to the metullurgical student. Their importance is shown by the fact that though the theoretical conclusions which I based upon them have been several times attacked, not one of my critics has made the slightest contribution to

By J. A. Herrick Nashua

IN this country steel made in a Siemens furnace or Bessemer converter, is generally tapped into a ladle or shoe, and then drawn through an aperture in its base into the various moulds. In order to regulate the flow of the molten mass a refractory valve is arranged at the aperture. A plumbago nozzle is fixed firmly in this aperture, and a stopper of like material is fitted to it, making a socket valve. In order to raise and depress this stopper at will, a rod is fastened-to it, extending through, the metal and over the brim of the ladle, where it is bent back in a half circle and secured in a slide. This slide plays vertically in a frame, permanently fastened to the outside of the ladle, and is moved by a lever having as a fulcrum a pin fixed in this frame, one end, of the lever being temporarily fixed to the slide, and the other end being moved by hand. Reference being had to the drawing (see Plate 1, Fig. 1), E is the nozzle, D is the stopper, A is the rod, protected as hereinafter described, C is the cast-iron framework, B is the wrought-iron slide, B' is the offset into which the rod, A, enters, and is secured in the usual manner by a key, a. Section J, K, shows the manner of hanging the lever. J is a pin attached to the slide by which the end of the lever raises the slide, B. J is the fulcrum fastened to the frame, C. K (Fig. 1) is a hand-nut fastening the slide, B, to the frame, C, at will. Fig. 2 is a side elevation of ladle, showing the outside working of the parts above described. It is the common practice to protect the rod, A, by a coating of clay and fire-sand, kneaded to the right consistency and applied to the rod, and then thoroughly dried. Just before casting, the plumbago stopper, D, is heated at its extremity to redness separate from the ladle and, at the moment of pouring, is placed in the ladle and slide, and adjusted as well as practicable. Some very serious defects ensue, causing much trouble and vexation as well as actual loss. The fire-clay coating in drying becomes cracked and seamy, and at its best is more or less loose on the rod. The hot metal sometimes cuts

Jan 1, 1879

By Martin Mayers

IT has long been recognized that it would be highly desirable to be able to predict the temperatures at various points in a burning fuel bed and their variations with changes of the properties of the fuel and the rate of air supply. Experimental investigations of fuel-bed tempera-tures1-4 have not been lacking, but the absence of any theoretical back-ground has made it impossible to use the results of these tests as a basis for prediction, except in a very general way. A mathematical analysis5, based on a somewhat simplified theory of the distribution of heat in a, fuel bed, has recently been completed by the author. Even though numerical values of some of the coefficients are not. known, the calcula-tions result in some conclusions of general significance. Thus, for example, it appears that when the temperatures throughout the fuel bed can be calculated, the rate at which ignition of the fuel by underfeed action can be maintained can also be calculated. The uncertainty concerning the values of the coefficients referred to above is a serious limitation on the use of that method. The following paper presents a discussion of these coefficients and includes estimates of their values based on the data now available. A brief description of the theory on which the analysis is based, and some results of the calculations showing their degree of agreement with experimental results, are presented by way of introduction to the discussion of, the coefficients. For a more extended discussion of the theory, see the A.S.M.E. paper5.

Jan 1, 1937

By Raymond Mancha

TO determine the optimum inside dimension of an airshaft, it is necessary to strike the proper balance between the cost of power for air friction and turbulence losses within the airshaft, on the one hand, and the cost of sinking the airshaft, on the other. An airshaft larger than necessary is extravagant because the increased amortization rate exceeds the reduction in power cost. Conversely, an airshaft smaller than is needed wastes more power than can be justified by the corresponding reduction in amortization rate. The airshaft power is a function of the air volume Q cu. ft. per min. and the air-pressure drop p in. water gauge across the airshaft. † The airshaft pressure drop is calculated by the formula: R X l X O X Q2 P= 5-2 X A3 wherein R is the air-friction coefficient for the portion of the airshaft 1 ft. deep, 0 ft. in perimeter and A sq. ft. in area, when passing an air volume of Q cu. ft. per minute. The airpower w kw. dissipated within the airshaft is computed by the formula: w= 0.746Q X P 6345 With a combined over-all unit efficiency of the fan and drive of E per cent, the air-shaft power requirements become W = 100w There are 8760 hours per year, so with energy at I cent per kilowatt-hour the annual cost per kilowatt for continuous operation is $87.60; therefore, with energy at C¢ per kw-hr. the annual airshaft power cost MI dollars per year becomes: M1 = 87.60W X C which, expressed by the component parts, becomes: M1 V 5.2X4' / XQ Z 0.746 X 100 X 87.60 X C V 60 X E ) The amortization rate a dollars per year per dollar invested includes both depreciation and interest on the investment. These in turn involve the expected useful life of the airshaft and available molletary interest rate. For the purpose of this discussion the cost of airshaft sinking is assumed to comprise a fixed move-in charge Y dollars, which covers the cost of transporting, erecting and removing the shaft-sinking equipment and is independent of the air-shaft size. Also, it is assumed that the cost of shaft lining, if any, is fixed at $X per cu. yd. of lining material and that excava-

Jan 1, 1947

By Raymond J. Kujawa

For general purposes, insulating materials may be any of those mineral substances that provide a barrier between a desired human environmental feature and an unwanted condition. In this sense, radiation shields, electrical insulations, cryogenic insulation, and acoustical barriers would qualify. For this chapter only the thermal and acoustic insulations used for the median range of normal comfort control will be covered. Because of their magnitude and complexity the other fields are left to other chapters. In another sense, this section deals only with the ultra-lightweight aggregates and insulations, rather than the multitude of light-weight structural materials. Definitions and Uses The insulating materials covered in this chapter are the three groups of mineral products that provide thermal or acoustic barriers through the median temperatures encountered in home and industry. The three mineral categories are perlite, vermiculite, and the silicate wools whether they be categorized as glass, mineral, or rock. Perlites are those amorphous aluminum silicates with minor impurities that take the form of a felsitic, glassy lava possessing a pearl-like luster and concentric cracking. In a more commercial sense the term is used to describe either the natural or processed acidic, volcanic glass, containing from 2 to 5% combined water, that may be converted to a frothy mass by heating rapidly to the softening point. Vermiculites are micaceous, hydrated magnesium iron aluminum sheet silicates of varying composition. Commercial vermiculites are any of these sheet silicates that are capable of sufficient expansion on rapid heating to make an acceptable, highly porous product. Mineral wools, rock wools, silicate cottons, glass fiber are generic names for manufactured fibers in which the fiber forming substance may be slag, certain rocks, or glass. The fibers may be made by a blowing or spinning process. The resultant fibers may be felted or matted or gathered in the manner best suited to the use. The three groups may be used competitively to insulate ceilings and walls. The fibers have strong advantages in this area as they may be manufactured in batts that are stable in residential wall construction. The perlites and vermiculites are more suited to insulate cores and cavities of masonry walls and as plaster and concrete aggregates for thermal insulations. Vermiculite is widely used for insulating attic floors. Because of manufacturing techniques and controls, the glass fibers have made great strides as composites in the plastics industry but only a few of these uses classify in the insulation category.

Jan 1, 1975

By T. Sterry Hunt

IT is now five years Since I called the attention of the Institute to the industrial importance of the coal and the iron ores of the Hocking Valley in Southeastern Ohio, and in a pamphlet on the region published Soon after, in 1874, endeavored to resume the principal facts then known respecting it, including the observations of the geological survey of Ohio, made and published up to the time by Professors Andrews and Wormley, together with an estimate of the probable future of the region, and its relations to the coal and iron markets of the country. Since that time the labors of the Geological Survey have included a further Study of the coal by Prof. Edward Orton, the results of which will be awaited with much interest. I may say from my knowledge of them, that while confirming the general conclusions of his predecessors, he has been enabled to add much to our knowledge as regards the correlation of the various members in different parts of the coal-field, and to Show more clearly the positions and the importance of the ore-beds in the Hocking Valley region. The only ore mined in that vicinity previous to 1874, was below what is called the Great Vein or No. VI coal, and to the west of what is known as the Hocking Valley coal-field, and although experiments in a few furnaces in the State had Shown that this coal could be used with advantage in iron-Smelting there was not a single blast furnace within the field. My observations at that time, however, impressed me with the abundance of iron ore, not only below but above this important coal Seam, and I then ventured to express the opinion that this region, from its cheap and easily mined Smelting-coal, its native ores and limestones, and its geographical position and relations to the great markets of the West, and to the supply of rich iron-ores from Lake Superior, was destined at no distant time to become a great metallurgical centre, where iron could be made more cheaply than at any other equally accessible point in the country. The object of the present communication is to report progress, and to State how far my observations made in the region last month have justified the predictions of 1874. The five years which have elapsed have been, as all know, most unfavorable to the iron trade, and especially to new enterprises in untried regions, yet they have not passed without important industrial developments in the Hocking Valley, where not less than thirteen blast furnaces have been erected

Jan 1, 1879

By H. W. Camp

RESEARCH is defined, scientifically, as a "sys- tematic investigation of some phenomenon, and also a search for hidden treasures." Chemists tell us that the hidden treasures of petroleum are far richer than the .products which have been best known to us. However, these secrets will be discovered only through intensive and systematic, as well as scientific, industrial research. Indeed, the scope of the subject is so great that such an intensive research program should be assumed by a centralized organization supported by the petroleum industry as a whole. Such organization would assume the responsibilities for investigation of new products and development of markets for such products. Gasoline, the chief product of the petroleum industry, has become a cheap commodity. The continual un-controlled overproduction of crude petroleum, the in-tensive competitive condition in the marketing of petro-leum products and the increase of refining efficiency and installing of cracking facilities, have all combined to lower the market value of gasoline. The lower cost of gasoline has all been passed on to the purchaser in the form of lower prices so that today the most important product can scarcely be manufactured at a profit. In other fields, manufacturing industries have diversified their products when faced by a similar situation. Thus, they have been able to widen their marketing outlook. Why cannot the petroleum industry employ the same tactics ? Right now we are hearing much discussion concerning the development of a wider market for existing petro-leum products and new products for existing or prospec-tive markets. For instance, we can cite recent develop-ments for use of propane, butane, and ethylene. Butane has been found to be an efficient and inexpensive re-frigerant, especially adapted to home refrigerating sys-tems. Propane and butane fractions of natural gasoline may be shipped under pressure and may be used as a substitute for acetylene in cutting torches in connection with oxygen. There is a possibility of substituting butane for gas oil in the carbureting of coal gas, as we know that butane contains practically the gas enrich-ment as the same volume of gas oil and should prove to be a superior product for this function. Ethylene, a hydrocarbon present in cracked gases, is finding an outlet for the artificial ripening of green fruits. The following table . shows the more general use of petro-leum products as now established.

Jan 4, 1928

By John A. Church

IN the year 1874, when the price of pig-iron was still high, that staple product became the subject of discussion in the newspapers and among those philosophers who are determined to know the "reason why" for all things. The object of the inquiry was to find out why iron did not fall in price as much as some other things had fallen. Indeed, there seemed to be an impression that iron and gold ought to move on nearly parallel lines, for the fact was constantly brought forward that iron then cost twice as much as it did before the war, though gold had returned to within twelve or fifteen per cent. of its former value. After some time the papers, by what seemed to be nearly unanimous consent, reached the conclusion that the maintenance of high prices was the work of the furnace proprietors, who, as the result of their shrewdness, were pocketing enormous profits. No proof was given to support this opinion, and the figures of cost and sale that were produced were of the most general kind, and used in the most vague manner. Visiting the president of the Thomas Iron Company, whose great works at Hokendaqua and Catasauqua, in Pennsylvania, are so well known as the largest and among the best conducted in America, I found him quite willing to meet the vague suspicions of the newspaper wiseacres, by a publication of the figures contained in the furnace-books of his company. These were accordingly given to the world through the Engineering and Mining Journal, and attracted the general attention they so well deserve. Though my own name became connected with these statistics, from the fact that I used them as the basis for the first attempt ever made to calculate the furnace economy of an American works, I can, without the suspicion of egotism, say that the statistics referred to are the most valuable contribution the literature of American blast-furnace work has yet received, for their interest is independent of personal considerations, and due entirely to the fact that they represent faithfully the details of practice in one of the most prominent American works. They are an exact transcript of the furnace-books, and form a body of accurate information of the greatest value to the metallurgical student. Their importance is shown by the fact that though the theoretical conclusions which I based upon them have been several times attacked, not one of my critics has made the slightest contribution to

Jan 1, 1876

By Elliott J. Roberts

In spite of the fact that the percentage of true colloids in an ore grind is very small,' these pulps exhibit many of the properties of true colloidal suspensions. A quartz particle, appreciably finer than 10 microns in diameter, has a settling rate so low that at a dilution of 5:l or over, the capacity of a settling tank to settle such particles would be uneconomical if the individual particle rate prevailed. However, by grouping the finer particles into aggregates or flocs, the settling rate can be increased to an economical value. The colloidal chemistry of pulp thickening is thus chiefly concerned with particles having diameters of between 1 and 10 microns, although particles as coarse as 40 microns in diameter are more or less involved. These particles must be associated in such a manner that they settle at an economical rate and give a clear, supernatant liquid or overflow. The treatment of the subject may be divided into three phases, cach phase having a more or less different colloidal aspect. The first phase is the problem of getting the pulp or suspension into the proper condition of flocculence; the second is the behavior of the flocculent pulp in its initial and intermediate stages of settling; the third is the behavior of the flocs in the find period of settling or thickening stage. Let us look first into the methods and mechanism of obtaining the flocs and then consider their behavior and properties. Flocculation Colloids are merely ordinary substances reduced to a very small particle size, the upper limit being placed by definition at 1 micron (0.001 mm.) diameter by the soil chemists and at from 0.2 to 0.1 micron by various other colloid chemists. The lower limit is reached only when the particles approach molecular dimensions. The term L'colloid" should not necessarily imply lack of crystallinity. Particles as small as 0.01 to 0.02 micron give perfect X-ray patterns, while with 0.005 micron particles the bands on the powder photograph are merely broaderled and diffused.2

Jan 1, 1935