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By B. M. Larsen, T. E. Brower

In an earlier paper1 we discussed a simple, rapid method of taking samples of liquid steel and analyzing them for oxygen, which, though possibly not absolutely accurate (as is likewise true of all other methods), certainly yields results that are satisfactorily consistent. Accordingly, samples from hundreds of heats ill different shops were analyzed for oxygen, with results sufficient in number to be handled statistically and permit estimation of some general trends. Measurements were made in acid as well as in basic open hearths, throughout the refining period, to learn how stirring, blocking, adding ore or lime or sand, affects the oxygen content of the bath; we also followed the changes brought about by tapping, teeming, and deoxidizing. Some of these results, discussed in an earlier paper,2 bring out the dominant role of the carbon-oxygen reaction in regulating degree of oxidation both of metal and of slag, also the marked variability of concentration of dissolved oxygen [0] in excess of that which would be in equilibrium with carbon and with carbon monoxide at a partial pressure of one atmosphere. As a logical beginning on this complex problem, we take up in the present paper the variability of this excess oxygen, A[O], when other factors are as constant as they ever are in open-hearth operation; namely, toward the end of the refining period, when the bath may be regarded as in the comparatively steady state it approaches in absence of disturbing factors. This condition was chosen because by that time the significant reactions, except carbon oxidation, between slag and metal have come to substantial equilibrium; this facilitates interpretation of the complex situation and thus perinits more definite conclusions to be drawn. This excess concentration of oxygen, A[O], in the metal is needed, of course, to make the steelmaking process go at a reasonable rate; alternatively it may be regarded as a measure of the virtual pressure increment above one atmosphere, or of the degree of supersaturation, of carbon monoxide in the metal. According to our measurements, the excess concentration A[0] in liquid steel varies from about 0.009 to 0,035 per cent oxygen by weight. It is quite sensitive to change of conditions, being altered temporarily by operations such as stirring with green poles, additions of ore, lime, or sand; but as the disturbance works itself out, it resumes a level within the intermediate range characteristic of the steady state. The conditions most common in average furnace practice are covered by the following: i[O] Usual Per Cent Oxygen by Conditions Weight 1. Vigorous lime boil........... o.oog-0.01s 2. Steady state................ o.or;-0.025 3. Working of ore.............. o.023-0.035 Thus when the bath can be regarded as in a reasonably steady state—that is, when it is boiling normally, is at proper temperature with a well-shaped slag, and has been free from disturbing effects during the preceding half hour—A[0] returns from

Jan 1, 1948

By Carter S. Cole

Mr. Chairman, Fellow Members and Guests, our chairman this morning got over into the geneological field, so perhaps I may be pardoned if I revert to some of my ancestral training and give you a text. I always like to talk about some special little text that may illustrate what we want to say. So the text that I will take for this afternoon is a very simple one, "Win the War." That is the guide for all of our actions, or should be. We should question everything we do to see what it does to contribute to winning the war. If we fail to do that, nothing else is going to count. On the wall of the office of one of the branch chiefs in the Copper Division in Washington there is a little slogan which I think we should take very deeply to heart, "The difficult we do right away. The impossible takes a little longer." I think that is a very good guide for us to follow in the work that lies ahead of us in the metallurgical field and in the handling of these secondary metals and the things that result therefrom. My subject is "Conservation and Specifications." Some people would wonder just where that fits in, and how you might define "conservation." One very good definition would be "the utmost use of our resources." If you will pardon my going back to some of my earlier experience for a little simile, those of you who know me know that for ten years after the last war I was in the railroad business. If we are with the engineman in a cab, and we have a green signal ahead of us, that is a clear signal and tells us to proceed at full authorized speed. Now suppose we come to a yellow signal that is caution, slow down to one-half authorized speed and be prepared to stop. Now if you do slow down, the chances are that that obstruction that was ahead of you will move out of the road, and you may get another yellow or caution signal at the next block, and be able to keep going at a slow speed. As of the date of Pearl Harbor our tin supply took on a very yellow tinge, and it threw the caution sign right in our faces. If we had not heeded that sign, and cut down our consumption of tin, we would not have any today; but because we have done so we are in a much better position today than we were a year ago, that is comparing our visible supply with our present rate of consumption as contrasted with the visible supply a year ago and our then rate of consumption.

Jan 1, 1943

In the period considered all coal produced was used locally, and the totals in Table 43 are estimated from the few data available. [ ]

Jan 1, 1942

By C. E. Nelson, T. E. Leontis

THE properties and casting characteristics of sand-cast Mg-Al-Zn alloys, used commercially in this country and abroad, have been discussed in a number of articles during the past few years.'-" In addition, broad surveys of many compositions in the magnesium corner of the Mg-Al-Zn diagram between 0 and 12 pct A1 and 0 and 6 pct Zn have been presented by Busk and Marande7 and by Fox." The purpose of this paper is to furnish a comprehensive survey of the changes in tensile properties, micro-structure, and dimensional stability of two magnesium alloys, AZ92A and AZ63A,+ as a function of aging time and temperature after solution heat treatment. Rates of precipitation in Mg-Al-Zn alloys are slow enough so that a substantially homogeneous, supersaturated solid solution can be maintained even when these alloys are air-cooled from the heat-treating temperature. Consequently, even though it has been demonstrated9 10 that significantly higher strengths can be developed in some alloys in the aged condition by quenching rather than air cooling from the heat-treating temperature, general practice is to air-cool magnesium alloys. All the work discussed in this paper is based, therefore, on aging studies performed on material air-cooled from the heat-treating temperature. This investigation was intended to be a study of commercially practical aging cycles; the tensile properties were determined, therefore, up to aging times of 25-hr duration. The alloys, used in this investigation were prepared in the laboratory by remelting commercial ingots of the appropriate composition according to the procedures described in a previous paper" as the "crucible method." All melts were given the standard superheating treatment in order to insure the maintenance of a uniform grain size of 0.003 to 0.004 in. Standard test bars, 61/2 in. long with a 2½ in. long reduced section having a diameter of Y2 in., were cast from these melts in green-sand molds using a four-bar pattern. The alloys were heat treated according to the following schedules: AZ92A alloy: 500" to 780°F in 2 hr + 780°F (24 hr) AZ63Aalloy: 500" to740°Fin2 hr + 740°F (16hr) In commercial practice," AZ92A alloy is heat treated at 770°F for 18 hr and AZ63A alloy is heat treated at 730°F for 10 hr. The slightly higher temperatures and longer periods of heat treatment were used in order to obtain as homogeneous a solid solution as possible and thus to minimize inconsistencies in the

Jan 1, 1952

By Ernest Klepetko

A notable amount of fossil resin exists in many of the bituminous coal beds of Utah, The upper part of these show a marked concentration of resin, which occurs primarily in the fracture seams. In general, these seams are less than 1/8 in. thick, but it is not uncommon to find coal with areas as thick as 3/8 in. The resin is of the hard kauri variety, with coloration varying from deep blood red to lemon yellow and almost colorless. There is also an almost black variety, which is not readily soluble in the same solvents as the lighter colored resins. These resins are valuable for many industrial purposes. When refined, they are suitable for uses similar to those for which lac resins are usually employed. They are particularly desirable for preparing dielectric varnishes. They are also desirable in preparing printing inks, waterproofing agents, special synthetic rubbers and rubber cements, They are especially suitable as an admixture in synthetic rubbers and cements, as they supply the essential tackiness the synthetics lack. The following chemical trade characteristics' have been found by Inter-Chemical Co. research chemists in the refined resins: Specific gravity (melted)....... I. 03 -1.06 Acid number.................. 6-8 Softening point, mercury method 160°-165°C Iodine valus (Wijs)............ 140-150 Refractive index............... 1.544 Color (Hellige, 25 pct toluol)... 14 Molecular weight, average...... 732 purity, 99 + pct pure hydrocarbon "Unaffected by alkalies and resistant to one hour fusion with solid potassium hydroxide. Completely soluble in aliphatic and aromatic hydrocarbons. Insoluble in alcohols, ethyl acetate and other commonly used alcohols and esters. Compatible with natural and synthetic rubbers, chlorinated and cyclized rubbers, waxes, vegetable oils, mineral oils, rosin, ester gum, phenolic and modified phenolic resins and other natural and synthetic resins of like solvent solubility."* The recovery and refining of these fossil resins has been the subject of much research work and has intrigued many investigators. Broadly speaking, the problem involves separation of the resin from the coal into a very high-grade concentrate, and subsequent treatment of this concentrate to produce an acceptable refined resin for its various usages. Obviously it is also desirable to recover the residua] coal without excessive size degradation. The late W. D. Green, concentration engineer for Combined Metals Reduction CO., obtained U. S. Patent No. 1773997 for the recovery of resin from coal through

Jan 1, 1949

By Ernest Klepetko

A notable amount of fossil resin exists in many of the bituminous coal beds of Utah. The upper part of these show a marked concentration of resin, which occurs primarily in the fracture seams. In general, these seams are less than 1/8 in. thick, but it is not uncommon to find coal with areas as thick as 3/8 inches. The resin is of the hard kauri variety, with coloration varying from deep blood red to lemon yellow and almost colorless. There is also an almost black variety, which is not readily soluble in the same solvents as the lighter colored resins. These resins are valuable for many industrial purposes. When refined, they are suitable for uses similar to those for which lac resins are usually employed. They are particularly desirable for preparing dielectric varnishes. They are also desirable in preparing printing inks, waterproofing agents, special synthetic rubbers and rubber cements. They are especially suitable as an admixture in synthetic rubbers and cements, as they supply the essential tackiness the synthetics lack. The following chemical trade characteristics have been found by Inter-Chemical Co. research chemists in the refined resins: Specific gravity (melted)....... I .03 -I.06 Acid number.................. 6-8 Softening point, mercury method 160º-165ºC Iodine value (Wijs)............ 140-150 Refractive index............... 1.544 Color (Hellige, 25 pct toluol)... 14 Molecular weight, average...... 732 Purity, 99 + pct pure hydrocarbon "Unaffected by alkalies and resistant to one hour fusion with solid potassium hydroxide. Completely soluble in aliphatic and aromatic hydrocarbons. Insoluble in alcohols, ethyl acetate and other commonly used alcohols and esters. Compatible with natural and synthetic rubbers, chlorinated and cyclized rubbers, waxes, vegetable oils, mineral oils, rosin, ester gum, phenolic and modified phenolic resins and other natural and synthetic resins of like solvent solubility."* The recovery and refining of these fossil resins has been the subject of much research work and has intrigued many investigators. Broadly speaking, the problem involves separation of the resin from the coal into a very high-grade concentrate, and subsequent treatment of this concentrate to produce an acceptable refined resin for its various usages. Obviously it is also desirable to recover the residual coal without excessive size degradation. The late W. D. Green, concentration ennineeru for Combined Metals Reduction CO., obtained U, S. Patent No. 1773997 for the recovery of resin from coal through

Jan 1, 1948

By Ernest Klepetko

A notable amount of fossil resin exists in many of the bituminous coal beds of Utah. The upper part of these show a marked concentration of resin, which occurs primarily in the fracture seams. In general, these seams are less than 1/8 in. thick, but it is not uncommon to find coal with areas as thick as 3/8 inches. The resin is of the hard kauri variety, with coloration varying from deep blood red to lemon yellow and almost colorless. There is also an almost black variety, which is not readily soluble in the same solvents as the lighter colored resins. These resins are valuable for many industrial purposes. When refined, they are suitable for uses similar to those for which lac resins are usually employed. They are particularly desirable for preparing dielectric varnishes. They are also desirable in preparing printing inks, waterproofing agents, special synthetic rubbers and rubber cements. They are especially suitable as an admixture in synthetic rubbers and cements, as they supply the essential tackiness the synthetics lack. The following chemical trade characteristics have been found by Inter-Chemical Co. research chemists in the refined resins: Specific gravity (melted)....... I .03 -I.06 Acid number.................. 6-8 Softening point, mercury method 160º-165ºC Iodine value (Wijs)............ 140-150 Refractive index............... 1.544 Color (Hellige, 25 pct toluol)... 14 Molecular weight, average...... 732 Purity, 99 + pct pure hydrocarbon "Unaffected by alkalies and resistant to one hour fusion with solid potassium hydroxide. Completely soluble in aliphatic and aromatic hydrocarbons. Insoluble in alcohols, ethyl acetate and other commonly used alcohols and esters. Compatible with natural and synthetic rubbers, chlorinated and cyclized rubbers, waxes, vegetable oils, mineral oils, rosin, ester gum, phenolic and modified phenolic resins and other natural and synthetic resins of like solvent solubility."* The recovery and refining of these fossil resins has been the subject of much research work and has intrigued many investigators. Broadly speaking, the problem involves separation of the resin from the coal into a very high-grade concentrate, and subsequent treatment of this concentrate to produce an acceptable refined resin for its various usages. Obviously it is also desirable to recover the residual coal without excessive size degradation. The late W. D. Green, concentration ennineeru for Combined Metals Reduction CO., obtained U, S. Patent No. 1773997 for the recovery of resin from coal through

Jan 1, 1948

By Richard Hodgson

FMC Corporation, at their mine and soda ash refinery near Green River, Wyoming, currently mines in excess of 3 million tons per year of trona. Upon completion of the current expansion, the mine will be producing in excess of 4.0 million tons per year. The single level mine, approximately 1,500 feet in depth, is currently serviced by five (5) concrete lined circular shafts varying in diameter from 12 ft. to 24 ft. A sixth shaft is complete, but not yet operational and the seventh is currently being sunk. Two of the shafts are equipped with single drum hoists. The original production shaft is equipped with a double drum hoist. The newest production shaft and the main service shaft are both equipped with ground mounted friction hoists. These friction hoists have given excellent service and another will soon be installed as a man and material hoist at No. 7 Shaft. There are a number of advantages that the ground mounted hoist has over a tower mounted hoist. There are also operating problems common to both. FMC's original experience with ground mounted friction hoists began in 1962 with the conversion of a single drum hoist to a friction hoist. The converted hoist was an Ottumwa with a 5 ft. diameter drum and a 4 ft. face. This hoist had been installed at the No. 3 Shaft for some years prior to its conversion to a friction hoist. At the time the conversion of this hoist was made, there were no friction hoists in service in Wyoming. Wyoming mining laws required that all conveyances carrying men be equipped with safety dogs. Since it was desired that wire rope guides be used, safety dogs were impractical. Agreement was reached with the State Mine Inspectors that safety dogs would not be necessary provided that recommended rope safety factors for hoisting men would still be maintained if one hoisting rope was broken. Since-the shaft is approximately 1,500 ft. deep, the recommended safety factor is 6.0 so that this installation has a safety factor in excess of 8.0 for hoisting men when new ropes have been installed. The hoist conversion was engineered by Lake Shore, Incorporated. The friction ring was made in halves and bolted over the original drum face which had been machined to remove the grooves. The ring provided for four 3/4 in. diameter ropes on 8 inch center to center spacing. The pitch diameter of the modified drum was 72 inches. The grove liners are hald in place by hard-wood wedges bolted to the drum. The other modification required by the conversion was an increase in size of bearing caps and the hold-down bolts because of the increased force tending to lift the drum.

Jan 1, 1975

By M. M., Fine

In a laboratory study of grinding and classification' of silica sand, a satisfactory means of producing the medium-fine specification sand desired by producers of flint-glass containers was developed. The best procedure consisted of ball-mill grinding and double classification, which gave a properly sized sand containing less iron than the feed.

Jan 1, 1950

By Persifor Frazer

The following notes on the Whopper and adjoining mines in the Gunnison district of Colorado mere made in the spring of this year. The time chosen for the author to visit the region was, unfortunately, the most unfavorable of an exceptionably unfavorable year. About the middle of May all the hill slopes, which at this period of the pear are generally covered with pasture, were thickly covered with snow. The unusually large precipitation of this Tear caused loacal mountain torrents at every few hundred feet, which wore away the oft foothills into gulches, gouged great chasms out of the roads, and transformed miles of usually dry soil into dangerous quagmires. Travel was totally interrupted for weeks, except on horseback or afoot, and even then with great difficulty and some danger. The Whopper mine is situated on the Whopper Mountain, about two miles from the headwaters of Rock Creek, and on the right hank of that stream. The Whopper Creek flows into Rock Creek horn the east, and, by a precipitous descent, offers excellent facilities for its utilization as a source of power. This stream, which pours past the picturesque Whopper Cabin about thirty tons of water a minute, has a fall of 100 feet in 400 yards, and is said to be a stream of some size, even at the seasons of the year when drought prevails. The Whopper claim extends down the hill a distance of about 250 feet to its intersection with the Whopper Creek (on the other side of which is a small tunnel on its extension called the "Teller") and over the steep hill northwest to the limits of the claim about 1250 feet. The part of the mountain in which this mine is situated is remarkable for its splendid forest, the spruce, fir, and quaking asp covering the mountain-sides with a green growth of valuable timber. The distance from Gothic City to this mine is about eight miles along the valleys of East River and Rock Creek, and on the divide which separates them. The elevation of Gothic City is given from the engineer's notes as 9500 feet above sea-level, and the mean of several observations with a Beck watch-barometer made the elevation of Whopper Cabin (which is about fifteen feet above the floor of the Whopper upper tunnel) about 1260 feet above Skiles's Cabin in Gothic City. The record of this instrument must, how-

Jan 1, 1881

By Persifor Frazer

THE following notes on the Whopper and adjoining mines in the Gunnison district of Colorado were made in the spring of this year. The time chosen for the author to visit the region was, unfortunately, the most unfavorable of an exceptionably unfavorable year. About the middle of May all the hill slopes, which at this period of the year are generally covered with pasture, were thickly covered with snow. The unusually large precipitation of this year caused local mountain torrents at every few hundred feet, which wore away the soft foothills into gulches, gouged great chasms out of the roads, and transformed miles of usually dry soil into dangerous quagmires. Travel was totally interrupted for weeks, except on horseback or afoot, and even then with great difficulty and some danger. The Whopper mine is situated on the Whopper Mountain, about two miles from the headwaters of Rock Creek, and on the right bank of that stream. The Whopper Creek flows into Rock Creek from the east, and, by a precipitous descent, offers excellent facilities for its utilization as a source of power. This stream, which pours past the picturesque Whopper Cabin .about thirty tons of water a minute, has a fall of 100 feet in 400 yards, and is said to be a stream of some size, even at the seasons of the year when-drought prevails. The Whopper claim extends down the bill a distance of about 250 feet to its intersection with the Whopper Creek (on the other side of which is a small tunnel on its extension called the "Teller ") and over the steep hill northwest to the limits of the claim about 1250 feet. The part of the mountain in which this mine is situated is remarkable for its splendid forest, the spruce, fir, and quaking asp covering the mountain-sides with a green growth of valuable timber. The distance from Gothic City to this mine is about eight miles along the valleys of East River and Rock Creek, and on the divide which separates them. The elevation of Gothic City is given from the engineer's notes as 9500 feet above sea-level, and the mean of several observations with a Beck watch-barometer made the elevation of Whopper Cabin (which is about fifteen feet above the floor of the Whopper upper tunnel) about 1250 feet above Skiles's Cabin in Gothic City. The record of this instrument must, how-

Jan 1, 1881

By A. D. Brokaw

The so-called "paraffin dirt" of the Gulf Coast oil fields has been considered an indication of the possible presence of oil and gas, and not a few wells have been brought in solely on the basis of such evidence. In a sense, it may be empirically justified as evidence of the presence of oil or gas, though it cannot be said to be infallible. If the writer is correctly informed, its association with oil and gas was pointed out by Lee Hager some years ago, and while it is commonly mentioned by geologists and operators in conversation, no discussion seems to have found its way into print. The present interpretation is based on laboratory study rather than on field investigation, and is put forth with the hope of stimulating discussion which shall lead to more complete understanding. The term "paraffin dirt" has been applied to soils with a peculiar texture, which has been described as "curdy" or "rubbery." When moist, the material breaks much after the fashion of "green" cheese. It is rubbery under compression, but does not resemble rubber in tenacity or cohesion. When dry, the material ranges from hard clods to a horny mass of high tensile strength. The shrinkage in drying is very great, especially in the hornlike matter. The moist material ranges in color from dark brown in the specimens rich in organic matter to grayish in specimens containing more inorganic matter. All of the specimens studied were readily attacked by molds, which in some cases grew in great profusion on the samples. Samples exhibited a rather characteristic "swampy" or "mucky" odor when wet, and a characteristic odor of humic soils when moist. If the material is brought into suspension in water, very fine sand settles out and may be recovered by successive washing and decantation. The sand is almost entirely quartz, but contains occasional fragments of feldspar—more or less kaolinized and iron-stained. Practically all of the sand passes through a 100-mesh screen and the grains are extremely sharp —possibly below the limit of rounding. A flocculent mud, of clay and organic matter, remains in suspension for days. Some material is taken into solution in the water, imparting a slight tendency to froth when vigorously shaken. The results of partial analyses of four samples of "paraffin dirt," and, for comparison, one of a coastal plain soil are given in Table I.

Jan 1, 1920

By D. D. Todd, W. A. Oates

THERMODYNAMIC data for solutions are best derived from a combination of equilibrium and calorimetric studies. However, the accurate measurement of heats of mixing of metallic solutions at high temperatures presents considerable experimental difficulties, simple calorimeters1-3 giving

Jan 1, 1964

By Frank C. Greene

Drilling in Missouri in 1945 dropped slightly from the preceding year. The only notable development was that in the Ballard area in Bates County, where a number of farmers drilled private gas wells with an average depth of a little more than 30o feet. Table 1 gives a summary of activities by counties. The total footage drilled was 36,186 ft. of which 20,489 ft. was by cable tools and 15,697 ft. by rotary tools.

Jan 1, 1946

By C. J. Bechtoldt, H. C. Vacher

Quenched alloys, prepared by powder metallurgical techniques, were examined by microscopic and X-ray diffraction methods. The compositions and heat treatments were chosen so that the chromium and nickel solvuses could be determined and a range of composition and temperature, in which a eutectoid had been reported, could be explored in small intervals. The results showed no evidence of eutectoid reactions having taken place. ALLOYS containing iron, chromium, molybdenum, and nickel are extensively used in high-temperature applications. In order to provide basic information on the solid-state reactions that occur in such alloys, the National Bureau of Standards is engaged in an extensive study of the equilibrium phases in the binary, ternary, and quaternary systems involving these four metals. Attention was directed to the chromium-nickel system because a review of the literature showed conflicting data. A recent compendium1 of the constitution of binary alloys gives two diagrams for the chromium-nickel system, one a simple eutectic and the second a diagram showing a eutectoid and a eutectic. The eutectoid was the result of an allotropic transformation in a high-temperature solid-solution form of a chromium-rich phase called 0. The approximate temperature and composition of the eutectoid was 1200°C and 30 at. pct Ni. In the preliminary study, at the Bureau, no transformation was indicated in the chromium-rich phase of ternary and quaternary alloys in which chromium and nickel were major components. Similar results have been reported from time to time in the literature,2-8 In consequence of this situation, a systematic study was made of the constitution of heat-treated chromium-nickel alloys using metallographic and X-ray diffraction methods. The compositions of the alloys were selected so as to determine the boundaries of the chromium-rich and the nickel-rich phases and to explore in small intervals the ranges in composition and temperature in which the eutectoid had been reported. The results of this study are reported and discussed in the present paper. EXPERIMENTAL PROCEDURES Materials, Alloys, and Heat Treatments—The alloys were prepared by a powder metallurgy technique similar to that used in earlier work.9 Analyses of the materials used are given in Table I. Powders were mixed using a vibrator in 30-g batches of predetermined composition; 2-g pellets were made from the mixture by compacting at room temperature in a 1/2-in. diam mold under 60,000 lb per sq in. pressure. The pellets were sintered in dry hydrogen for 10 days at 1300°C. At the end of the sintering treatment the specimens were quenched in water, which caused a pale green film to form on the chromium-rich alloys and thin black scale to form on the nickel-rich alloys. The pellets after sintering were approximately 1/2 in. diam by 3/32 in. thick. The purification train9 was modified by inserting a tube of titanium turnings, heated at 700°C to increase the efficiency of the removal of oxgen and nitrogen. It was found in the earlier work that the sintering treatment lowered the carbon, oxygen, and nitrogen contents of chromium-rich alloys to 0.01, 0.01, and 0.004 wt pct, respectively, and that there was a loss of chromium. In order to ascertain the extent of this loss, the chromium contents of certain alloys were determined chemically. They included those alloys used to determine the parameter-composition curves and those of critical composition, used to determine the chromium-solvus microscopically; these analyses were made on samples after the final heat treatments. The mixed powder values for the chromium content of those alloys that were not analyzed were adjusted to conform to a smooth curve based on the chemically analyzed values for

Jan 1, 1962

By John A. Brown

Granules are used primarily as roofing material. From the earliest times, man has been faced with the basic problem of providing protection for himself, his family, and his property against the ravages of the weather. Basically, this problem is no different today than in the past, except that today the trend is to demand shelter which is also colorful and distinctive. There has been a gradual evolution from the thatched roof to the modem ranchstyle home. In his search for a more permanent and more attractive roof, the home owner has utilized many mineral materials. All granules, whether slate or colored granules, are referred to by the asphalt roofing industry as "Slate Granules." Early Roofing Materials The development of mineral roofing in the United States followed two trends: first, the slate industry, and second, the bituminous products. The early colonists were familiar with slab slate construction from Europe and it was natural for them to continue with this type of roofing. As early as 1780, the forerunners of the present bituminous products were finding favor. Those early products consisted of saturating burlap or similar material with crude tar or pitch. This type of roofing was soon improved by dusting a variety of materials on the surface of the roofing to prevent adhesion while in rolls. Such factors as fire resistance and protection from the actinic rays of the sun soon followed. This started the general pattern which is still followed today, that is, saturating felt materials and supplying a uniform grade of crushed mineral to the surface. In commercial and public buildings, metal roofs found early favor. The attractive green color of verdigris-coated copper became a symbol of churches and institutions of learning. Aluminum roofing has become economical for large structures and is finding limited popularity in rural areas. Tile, asbestos, and cement materials, being weather resistant, found early acclaim and are still popular. Today, by far the most widely used roofing materials in the United States are asphalt products. Two important characteristics-economy and weatherability-account for their popularity. Influence of Building Trends on Roofing The postwar building boom in 1947 had many attractive features for the American people. The ranch-style one story type of home seemed well suited for suburban developments which sprang up in such profusion. As the roof in modern home construction is one of the most conspicuous aspects of its architecture, the home owner could now express his tastes not only in paint and landscaping, but could also select an attractive and harmonious roof color. Variety of Minerals Used Many naturally occurring minerals are used today in the roofing industry. Most widely used (and most noticeable to the public) is the granulated mineral surfacing applied to asphalt products. Selected natural colored granules as well as artificially colored granules are

Jan 1, 1960

By Robert Henry Bradford

This investigation was undertaken at the suggestion of Prof. Henry M. Howe, of the Department of Metallurgy, Columbia University, who, in a letter to the author, dated October 23, 1900, wrote as follows, suggesting the subject of this dissertation : "The extraction of silver from copper mattes by either the Ziervogel or the Augustin process depends upon converting the silver into silver sulphate by means of the sulphuric anhydride evolved from the decomposition of ferrous sulphate and cupric sulphate, which are formed during the roasting operation itself from the iron and copper sulphides present. "It occurred to me, some time prior to the autumn of 1897, that these processes might be made much easier by adding to them, at the proper stage, ferrous or cupric sulphate, or both, in the form of green or blue vitriol. That is, instead of having to rely solely on our ability to generate these sulphates in this very delicate roasting operation, my idea was that we could add a small quantity of already-prepared sulphate at the proper state of roasting, viz., at or before the period when the solphatizing of the silver occurs. The comprehensive audit of the accounts of a mining company is extremely important in its relations to the legal situation and obligations of the corporation, the personal liability of the directors, and the interests of the investing public. A consideration of the subject as affecting the professional duties and fixing the responsibility of a mining engineer engaged in the expert examination of a mine or in charge of mining operations, is equally important, though this phase of the question is not often presented systematically.

Jan 1, 1903

By D. S. Sanders, E. W. Witcomb

FLOTATION tests, from which the flowsheet for the concentrator was determined, were made in a pilot mill at Chuquicamata and later comparative testing of full size flotation cells was done at the Andes Copper Mining Co. concentrator in Potrerillos. The principal sulphide copper mineral is chalcocite with varying amounts of covellite, enargite, and chalcopyrite. The oxidized portion is principally antlerite, a green basic copper sulphate. The gangue minerals include quartz, sericite, pyrite, feldspars and kaolin. Chuquicamata pit ores have proved to be hard grinding. The results of the flotation and metallurgical work prove that good extraction and concentrate grade can be obtained under a rather wide range of conditions. Metallurgy In general the metallurgy of the ore requires a fairly close control of the grind to the primary rougher flotation and of the regrind of the primary rougher concentrate before cleaning. Regrinding is necessary to reduce the insoluble content of the final concentrate since a large part of the middling combinations are between the copper and silica minerals. The alkalinity of the pulps can vary between wide limits and control of the percent solids gives the desired grind. Alkalinity Control Arroyo Salado water is supplied to the concentrator head tanks. It contains about 5000 ppm of salts but test work shows no deleterious effect. Actually this water permits a decrease of as much as 1 lb of lime per ton of ore as compared to San Pedro water, which is used for leaching oxide ore. About one quarter of the water flow through the concentrator will be new water from the reservoir. The remainder will be reclaimed from the thickeners. For primary grinding and rougher flotation, new and reclaimed water are combined in the head tanks. To avoid erratic results, only new water is used in the regrind system. Milk of lime is added to the rod mill feed chute to obtain the maximum benefit of mixing with the ore. This protects the equipment from corrosion due to entrained acids and soluble copper salts. Lime consumption is 3 to 5 lb per ton of ore. Grinding and Flotation The six bin gates over each belt feeder are opened in controlled combination and sequence to keep a live bed of ore in the bin to prevent arching and to obtain mixing. The milk of lime added ahead of the rod mill is regulated to suit rougher flotation requirements. The primary promoter reagent, Aerofloat 238, is added to the 10-mesh discharge of the rod mill as it is laundered to the ball mill scoop box. The classifier overflow is regulated to produce a grind of about 12 to 15 pct +65 mesh and 60 pct -200 mesh. A secondary promoter Z-4 (aml zanthate) and the pine oil frother are added in the overflow launder where a pH of 10 to 11 is maintained. Comparatively heavy beds of froth on the

Jan 1, 1952

By C. C. Wright, T. S. Spicer, R. G. Bowman

In recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation's fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. Production of Fly-ash The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air

Jan 1, 1944

By T. S. Spicer, C. C. Wright, R. G. Bowman

In recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation's fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. Production of Fly-ash The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air

Jan 1, 1944