Search Documents

By A. C. Fieldner

In November, 1926, the American Engineering Standards Committee (now the American Standards Association) called a meeting of representatives of various professional societies and industrial, educational and governmental organizations to consider what action, if any, should be taken on the classification of North American coals. This meeting was called because a system for the use classification of coal, proposed by George H. Ashley, had been referred to the committee by the Coal Mining Institute of America. This meeting, at Pittsburgh, was well attended and was definitely in favor of taking up the whole question of scientific and use classification of coals, including all the various ranks from lignite to anthracite. The American Society for Testing Materials was recommended as the sponsor organization to take charge of the work and organize the sectional committee according to the rules of the American Standards Association. The American Society for Testing Materials proceeded with the organization of the sectional committee, holding a meeting in Philadelphia, June 10, 1927. Officers were elected, regulations adopted, and general plans for carrying out the work were outlined. The total membership of 28 comprising the sectional committee consists of 8 producers, 2 distributors, 9 consumers and 9 members representing general and scientific interest. From this committee three technical committees of 10 to 12 members each were organized: Scientific Classification, H. J. Rose, chairman; Use Classification, W. H. Fulweiler, chairman; Marketing Practice, F. R. Wadleigh, chairman. The Technical Committee on Scientific Classification was requested to formulate a system of coal classification based on chemical and physical properties of coal and with reference to origin and constitution. The Technical Committee on Use Classification was charged with developing a system of classification, if possible, based primarily on the uses of coal and commercial practice; this system to be correlated with the scientific system as far as possible and desirable. The Technical Commitlee on Marketing Practice was formed to collect and collate information on commercial practice for the benefit of the other two committees. The first meetings of the technical committees were held on Nov. 17, 1927, and the first informal progress reports were submitted to the

Jan 1, 1930

By Earl Hunner

IT is common knowledge that the iron orebodies of the Mesabi range lie nearly horizontal and are of trough or blanket-like types. These orebodies are from a few feet to several hundred feet thick and vary from a few acres in extent to the size of the largest one, at Hibbing, Minn., which is over 1 mile wide and 3 miles long. They are covered with sand, boulder and clay overburden and occasionally, shallow depths of ledge material, varying in total depth from about 20 to 200 ft. Large areas are not capped with overlying ledge material; the top of the ore lies directly underneath the surface material. Because of the comparatively great tonnage of ore, open-pit mining has made tremendous strides since the first open-pit ore was shipped from this range by the Merritt brothers, from the Mountain iron mine in October, 1892, and along with the great development of open-pit mining on the Mesabi range has gone a tremendous change in the character of equipment used.

Jan 1, 1930

By Jose M. Sobral

Approximate figures for petroleum production in Argentina for 1929 show an increase of only about 300,000 bbl. over production for 1928. This increase is due to greater yield in the Plaza Huincul and in the Salta regions. Table 1 shows the distribution of production in the various fields of the whole country, using estimates for the later months of the year. The outlook for production remains about the same as in 1928. It is believed that in northern Argentina there are regions that contain oil, but they are yet unexplored. Notable traces of oil at depths between 1280 and 1390 m. have appeared in a 1500-m. boring in Comodoro Rivadavia, but their importance is unknown.

Jan 1, 1930

By Joseph Jensen

No outstanding example of an important producing unit operation exists in California today where the competitive drilling drainage feature is or was entirely eliminated We need not feel, however, that the thought of unit operation had its birth in 1924, when Henry L. Doherty named and sponsored it so strongly before the American Petroleum Institute and our own organization. No man or company in California ever drilled a wildcat well without exerting every possible effort to get all of the structure, so as to control drilling and avoid competition. Overproduction did not begin in 1923, so there has always been the wish to avoid it. In this state the practice of selling acreage around a wildcat has not been followed, except possibly in rare instances. The operator drilling the wildcat knew he must pay the bill alone, so he endeavored to get the benefit of his effort by tying up all of the land around his well and by so planning his different lease obligations as to avoid as much offsetting as possible. If he failed to get all of the land, it was because someone's price was too high, some other oil man also had the same idea and already held some lands, a competitor took leases away from him while his work was still incomplete, or (as was so often the case) the hidden structure when developed did not prove to be where the wildcatter thought it would be. The last named condition often led to a forced drilling campaign by the last leases secured and thus to serious drilling drainage problems. Ownership of the Land The land situation differs a great deal in various parts of the state. In the San Joaquin Valley, all the land is surveyed into sections and townships. Railroad land grants embraced a part of the land. In the areas that were developed at an early date, as at Kern River, Coalinga, McKittrick and the Sunset-Midway field, such land as the railroad company's diligent land department had been unable to sell for a song as grazing land still remained in its ownership. Operation and ownership

Jan 1, 1930

By E. S. Wheeler

The rapid increase in the use of monel metal and malleable nickel in the form of sheet, rod and tube has resulted in a similar increase in the demand for these metals in the form of castings. These castings range in size from small valves and pipe fittings weighing a few ounces to large centrifugal pumps, gate valves and marine propellers, some of the last weighing as much as 24,000 lb. A group of such castings is shown in Fig. 1. A large nickel agitator is shown in Fig. 2. Monel metal castings are widely used in accessories for steam power plants and in a variety of chemical plant equipment where the corrosion resistance, high strength and toughness characteristic of this metal render it particularly valuable. Nickel castings find extensive use in the construction of corrosion-resistant apparatus, and are often used in conjunction with wrought nickel sheet and tube in the fabrication of equipment for handling a variety of chemical and food products, particularly dairy products. In response to this demand for castings, numerous foundries have undertaken the production of castings of these metals and have met with varying degrees of success. The successful production of castings of monel metal and nickel requires careful attention to molding practice, proper melting equipment

Jan 1, 1930

By C. W. Lawr

The ores mined by the Santa Gertrudis Co. at Pachuca, Mexico, arc mainly silver-bearing; they also yield some gold and carry a little copper. Strong cyanide solutions are used to dissolve the silver and gold, and the mechanical loss of cyanide at the tailings filter has been considerable. Prior to the year 1923, the pulp, after agitation, was given a 35 to 37-min. wash with barren solution in a Butters-type leaf filter; the discharged slime cake was repulped and pumped into eight Merrill self-sluicing slime presses in which the slime was given a further wash with barren solution for 25 to 35 min., followed by a 10-min. water wash. At that time the barren solution titrated around 0.350 per cent. free KCN and 0.500 per cent. total KCN. (Aero brand cyanide is used.) It can readily be seen that a 10-min. water wash would leave considerable cyanide in the filter cake, which of course was a total loss. This averaged 0.522 kg. (1.15 Ib.) KCN per ton of solution. As the daily discharge to the dam was 1600 tons' of slime of a 2:1 ratio of liquid to solid, the value of this mechanical loss of cyanide was an important item and it's recovery held alluring possibilities. Principle of Cyanide-recovery Process As it had acquired the patent rights to theLayng (H. R.) and Halvor-sen (A. L.) processes, also those of Mills (L. D.) and Crowe (T. B.) after considerable experimental work in its own laboratory and at Tonopah, Nev., The Merrill Company of San Francisco early in 1923 notified the Mexican Corporation and compania de Santa Gertrudis of its process for the recovery of cyanide from weak wash solutions, or for the transference of cyanide from a foul mill solution to a clean alkaline solution. This method is known as the Mills-Crowe process, the principle of which is as follows: The solution from which the cyanidc is to be removed is made acid by bringing it into contact with sulfur dioxide (SO2). The acidified solution is the; transferred to a closed tank in which air and solution are brought into intimate contact. The air leaving the tank charged with HCN is then passed to another tank in which it is mixed with an alkaline solution,

Jan 1, 1930

By Gilbert Francklyn

The requirements of coals for the manufacture of coal gas, water gas and producer gas will be considered sparately and a short description of each gasmaking process will be given. In this report the term "gas coal" is confined to coals suitable for the manufacture of city gas in horizontal, inclined or vertical retorts. The report does not refer to coke-oven practice.' Briefly, the process of manufacture consists of distilling the coal at high temperature in an externally heated retort out of contact with the air. The products of distillation, consisting of gas, tar, ammonia, etc. are collected and purified. The residue consists of coke, which is removed from the retort at the end of the carbonizing period. To supply the heat required in the process, a portion of the coke produced is converted into producer gas, which is burned under the retort settings. Qualities of Gas Coals The chief qualities that coal must possess in order to be classified as a gas coal are as follows: 1. Gas Yield.—The coal must be capable of yielding gas in sufficient volume and of a satisfactory quality. The yield depends considerably upon the temperature of distillation; a higher temperature will give a larger yield of gas, but the qualit,y of gas (now measured by the British thermal units per cubic foot) will be lower, while a lower carbonizing temperature will give less gas of higher heating value. The true measure of the yield is the number of British thermal units produced in the gas from a given quantity of coal. This number is obtained by multiplying the cubic feet of gas from 1 lb. of coal by the British thermal units per cubic foot of gas; it is called B.t.u. feet per pound. It is found that the

Jan 1, 1930

By Arthur F. Taggart

Some years ago, A. M. Gaudin and one of the authors published a paper showing removal of tar acids from solution by sulfides preferentially as compared to gangues (specifically by galena as compared to quartz).' The underlying phenomenon was classed as adsorption, and the paper went on to develop the general thesis that so far as water-soluble frothing and collecting agents in flotation are concerned, the phenomenon of adsorption is one of controlling importance. Adsorption was defined in that paper as "a process of rearrangement of a system, which results in establishing a difference in concentration, as between the interfacial layers and the bulk of the phases, of a substance or substances initially uniformly dispersed in one or several of the phases." The paper went on to develop the relation between adsorption and surface cnergy according to Gibbs' equation (which may be thrown into the form U/c = KdT/dc, where U = excess concentration in surface layer, c = concentration, T = surface tension, and K is a constant), and pointed out that, according to this equation, degree of adsorption and change in surface tension vary directly. The present paper offers a somewhat different definition for the term adsorption; and sets up, in sweeping terms, the generalization that simple chemical reaction underlies the functioning of the flotation reagents which control mineral collection, when these reagents are soluble in and act from solution in the water of the pulp. Adsorption According to the modified definition, adsorption means concentration at an interface between different phases in a heterogeneous system (thus far the definition runs as before), by the action of some mechanism, of which nothing is properly implied in the word, and concerning which the user of the word is probably in entire ignorance. Thus defined,

Jan 1, 1930

By R. E. Grim

With the exception of the extreme northeastern part of the state, Mississippi lies wholly within the Gulf Coastal Plains. The largest structural feature definitely proved is the so-called Jackson structure1 in the central part of the state. This structure is mainly the result of the burial of an igneous ridge on the old sea floor. The ridge trended in a northwest direction from about the town of Jackson in Hinds County into southeastern Arkansas. The present structure is the burial of the ridge. Recent detailed surface work by major oil companies has suggested smaller structures in other parts of the state, but so far they have not been definitely proved. Also considerable magnetometer and seismographic work has been done in the northern and central part of the state. The results of the operation of the seismograph are not yet available, but the magnetometer located many "magnetic highs" in this part of the state. Outside of the area of the Jackson structure, the exact cause for this magnetic variation is not known. In a portion of south Mississippi, considerable seismographic work has been done recently in an attempt to locate salt domes. While the details are not available, it has apparently met with little success. Prospecting by districts during the past year may be summarized as follows: Five wells of importance were drilled in the Amory district of east Mississippi. This district comprises all or parts of Monroe, Lee, Itawamba, Prentiss, .Alcorn and Tishomingo counties. Small gas was discovered at about 2500 feet. Several wells were drilled in the. Jackson district which is located in part or all of Hinds, Rankin, Madison and Yazoo counties. Some of these wells were abandoned and one was shut down most of the year

Jan 1, 1930

By H. S. Martin

Although it was known some years ago at the Utah Copper Co. mills that fine grinding improved flotation recoveries, no accurate data were available until recently as to just how far the grinding could be carried economically. In 1923 the ultimate degree of fineness for flotation feed was supposed to be about 10 per cent. on 65 mesh, with approximately 55 per cent. through 200 mesh, which meant that most of the mineral would pass 100 mesh. At this time Garfield and Wilfley tables were used ahead of flotation and a good deal of the coarse mineral removed prior to the ball mill regrind. Shortly afterwards, mill-scale tests developed the fact that on a feed containing not over 10 per cent. +65-mesh material flotation alone would give a copper recovery equal to that obtained by the combination of tables and flotation, but that on much coarser feed the recovery with flotation alone was lowered. This was at a time when all the sulfide minerals were floated if possible, so that the only requisite was to grind fine enough to free the mineral from gangue. Earliest Use of Microscopic Examination of Tailings As early as 1921, the writer had attempted to determine by chemical analysis the relative proportions of copper minerals in tailings from an ore that made extremely poor flotation results. Chemical analysis was not satisfactory or conclusive, and samples of these tailings were sent to the U. S. Bureau of Mines Station at the University of Utah for microscopic examination. The question at that time was to determine, if possible, which copper minerals had been lost and why, but R. E. Head, in his report, revealed other interesting data. He said in part: Briefly stated, the mineral partieles or grains may be classified into scparate groups as follows: 1. Free grains of pyrite, chalcopyrite, chalcocite and bornite, respectively, which contain 110 other included sulfides; 2. Grains in which all three of the copper sulfides are representel (the core may be of chalcopyrite, partially altered to boruite, these two minerals being cntirely surrounded by a shell of chalcocite); 3. Grains composed of equal amounts of bornite and chalcocite or chalcopyrite and chalcocite. The grains of free mineral particles are perhaps the most numerous, taking the ore as a whole, but it is noticeable that of the grains of combined or associated sulfides

Jan 1, 1930

By Ionel I. Gardescu

Natural gas influences the movement of oil through reservoir rock by affecting the physical properties of the oil and the pressure within the reservoir. The presence of gas bubbles changes the laws of flow and the distribution of forces. The problem of flow of oil and gas through a porous rock is complex, and most authors, in order to analyze their problems, have found it necessary to make or accept certain generalized assumptions. Some of these assumptions, particularly the ones dealing with capillary phenomena and moleculnr forces, have not received sufficient attention and by lack of understanding have often been misinterpreted. Herold1 has called attention to the resistance offered by gas bubbles in capillary spaces and has drawn some interesting conclusions with regard to the action of natural gas in a reservoir rock. He has duplicated an experiment of the French physicist Jamin, has interpreted his findings in terms of molar mechanics, and, from experimental observations, has made a number of assumptions which he later applies in discussing problems of natural flow and recovery of oil. The Jamin action is an assumption because it lacks a physical proof and has never been determined quantitatively. Tickel12 attempts to develop a formula expressing the work performed by a distorted bubble. H. A. Wilson, in the recent publication of the American Petroleum Institute on the function of natural gas, discusses the phenomenon in terms of classical physics. Both contributions are incomplete and offer no experimental data. This paper includes a study of the static condition of equilibrium of gas and liquid bubbles confined to capillary spaces. In order to avoid any possible confusion, it is proposed to restrict the term "Jamin action"

Jan 1, 1930

By H. T. Matson

IN the Northern Rhodesia copper fields the size of the orebodies and the exceptionally consistent values over great distances made it possible to outline the ore with drill holes spaced at 1000-ft. intervals; in some cases, 2000-ft. intervals.. Owing to the fact that the size of the deposits made it very evident that much outside capital would have to be called in to develop them and, owing to the wide spacing of the holes, it was essential that the sampling of drill holes be as accurate as possible, so that outside examining engineers could adopt the results as trustworthy within the limits of accuracy of the drilling method. With this object in view, the field staffs of the Selection Trust group of companies have studied for the past three years, and are still studying, drill sampling in a very thorough manner, and for this reason it is felt that these notes may be of interest to engineers or students who are, or in the future may be, in charge of drilling operations. The orebodies in this field lie in shales and sandstones, more or less indurated, in the lower strata of the Roan series, and the copper mineralization is in the form of sulfides predominantly, with some oxidized copper minerals. Those interested in the geology and history of the area can find full details in a recent paper by Anton Gray and Russell J. Parker.1

Jan 1, 1930

By Robert E. Palmer

The Hawkesworth detachable drill steel shank and bit were invented by A. L. Hawkesworth, while he was a mechanical foreman for the Anaconda Copper Mining Co., at Butte, Mont. Mr. Hawkesworth died on June 16, 1925, at the time that his invention was practically a proved success. The first application for patents was made by him in November, 1918, and the bit is now being manufactured under patents issued in 1922 and 1923. The credit for its development in the early stages belongs to A. L. Hawkesworth, Roy S. Alley, Harry A. Gallwey, E. J. Bowman and various officials of the Anaconda Copper Mining Co. Later improvements, manufacturing problems and the direct usage in the mines were originated and perfected by the mechanical department under C. D. Woodward, E. R. Borcherdt, head of the Rock Drill Equipment Department, Robert E. Kelly of the Mechanical Department, and various operating department heads of the Anaconda Copper Mining Co. The author wishes to acknowledge the assistance of these officials in the preparation of this paper. Comparison of Costs Using Regular Drill Steel and Detachable Drill Steel In 1922 production was satisfactory and sufficient enough to warrant a complete installation in an operating mine. The study and tests were made at the Badger State mine, the production of which averaged 1200 tons of ore per day. E. R. Borcherdt, head of the rock drill equipment department, was in direct charge of the trials, installation, operating problems and records during the entire .period, arid still continues in that position. This mine is a typical Butte mine, operated through a standard four-compartment shaft, served by a double drum hoist and an auxiliary hoist. The texture of the ground and ore has all the variations from soft to very hard granite and sulfide ore with production from levels between the

Jan 1, 1930

By F. W. Bremmer

The experiments described in this paper constitute the preliminary work of an investigation outlined to determine the combined effects of steam and temperature on the endurance properties of certain steels. Essentially of a fundamental nature, it was found necessary, in order to make the investigation comprehensive, to test materials treated to give a wide range of properties. The work reported deals chiefly with nickel steel with one series of tests including nitriding steel. Such a study involves numerous variables, and requires an endurance-testing machine of rather special design. Testing Machines The testing machines used were designed by C. E. Weaver;l they are a modification of the White-Souther and McAdam types. Each was driven directly by an individual 1/2-hp. 115-volt direct-current motor, running at a speed of 2200 r.p.m. Fig. 1 shows the assembly drawing and Fig. 2, a photograph of one of the machines. Specimen B is held by the rotating specimen holder A inside the steam box F, which is closed at the top by a tight-fitting, elliptical cover G. The load is applied to the specimen through the rod D and bearing C. E is an oil pipe leading fromthe lubrication system to the bearing C. The steam, which comes from the power house, is admitted through an inlet (not shown in Fig. 1) at the side of the box, the drain being at the bottom. Steam packings were placed around the rod D and the rotating shaft at H, from which the water was drained by means of a vacuum, which usually showed a gage reading of about 10 in. The temperature was measured by a mercury thermometer, and the pressure by a steam gage. Method of Applying Load After the motor has been started and the specimen as a consequence put in rotation, the load is applied by placing the foot pedal A (Fig. 2) in contact with electromagnet B, the winding of which is connected electrically in series with the motor. This operation releases the support under the weights that constitute the load. By this means the load

Jan 1, 1930

By J. Walter Scott

IT is usual practice in the copper industry to use open horizontal molds for casting tough-pitch copper wire bars.1 A wire bar cast in this manner is partly characterized, by heavy wrinkles and a comparatively deep skin of oxide on the top of the bar, corresponding to the open side of the mold. On the theory that the rough, high-oxide surface might have an adverse effect on the rolling and drawing properties of a wire bar and might account for some of the irregularities of mill behavior, several bars which had been planed to remove the wrinkled surface were processed into wire. These bars responded to mill treatment more satisfactorily than did the regular wire bars. Realizing that machining the surface of one face of each bar would not be commercially feasible, it was decided that casting the metal into a vertical mold and cropping off the pouring end would accomplish. approximately the same result. Several wire bars of commercial size (250 lb.) were so cast and processed into wire for comparative test with bars cast in the usual horizontal molds. It is the purpose of this paper to present the results obtained from this investigation, in which commercial bar sizes and processing technique were used throughout. The results show that in general copper wire bars cast vertically are superior to those cast horizontally.

Jan 1, 1930

By O. C. Ralston

Flotation is now commonly practiced in alkaline ore pulps, yet little is known regarding the action of the alkaline solutions on the ore particles beyond the fact that films of oxidized material form. We wish to chronicle our discovery of the presence of soluble reducing agents in alkaline ore pulps of the United Verde, and present some data on lime consumption. During the grinding and flotation of a pyritic ore containing small amounts of ferrous sulfate and other soluble salts, an excess of lime was added to precipitate the salts, and filtered samples of the solution were titrated with standard permanganate solution. Even in pulps of high causticity an appreciable permanganate titration was always obtained, in spite of the fact that the solutions were shown to contain little iron. Investigation of the cause brought about the discovery of several previously unsuspected compounds in flotation pulps made from pyritic ore. Not only the reducing agents present had to be identified, but also the amount of dissolved oxygen, and a survey was finally made of the free oxygen content and reducing agents of the mill pulp in the concentrating mill at Clarkdale. A great many compounds might form, caused by oxidation of pyrite or other metal sulfides or by reaction between a lime solution and pyrite. The most probable compounds considered were calcium sulfides, polysul-fides, thiosulfates, and polythionates. Later it was discovered in the literature that in alkaline pulp polythionates do not exist and if introduced are decomposed into sulfites and thiosu1fates.l Any precipitated sulfur is changed by alkali into thiosulfate and polysulfide. Sulfites and sulfides react to form thiosulfate, so that in the end it is possible to have in an alkaline solution only thiosulfate and an excess either of sulfide or sulfite. Confirmatory tests were made and it was finally established that the alkaline mill pulps made from the United Verde ore contained

Jan 1, 1930

By C. E. Wood, E. P. Barrett, T. L. Joseph

The United States Bureau of Mines has been studying the blastfurnace process for about ten years. An experimental furnace was developed by the Burcau in cooperation with the Minnesota School of Mines Experiment Station, University of Minnesota. Many data have been obtained and published.' Royster, Joseph and Kinney §(48) found that the particle size of ore had an important effect upon the blast-furnace process. Kinne(28) stated: Economy in blast-furnace practice depends largely upon efficient gas-solid contact in the shaft of the furnace. If efficient work is not done in the shaft, the hearth and bosh will not function properly. A condition may be readily imagined where the particles of ore in the shaft are so large that the time entailed in the descent of these materials into the bosh is not sufficient to permit proper reduction and preparation prior to the time the ore enters the bosh of the furnace. Another condition may be pictured where the density of theatock column and the flow of stock is such that the ore will take one course and the gas another. Both of these examples will result in insufficient contact between the gas and the ore. Unreduced ore will reach the hearth, and the gas which has not been efficiently oxidized will reach the stock line. The result is the use of an excess of carbon in the smelting process. It is obvious that fine ore particles occurring in the ore as charged, or formed in the furnace due to heat and mechanical action, place a definite limitation upon the efficiency of the operation. There is also an economic loss of fine material as dust. Effect of Size of Material Kinney reported (p. 83(29)) the reduction of iron oxides between planes at three furnaces as given in Table 1. The Chicago furnace was operated on Lake ores. Distribution of gas was not good and much of the charge passed into the hearth before the iron oxide was reduced. The Holt furnace was operated on coarse ore. Distribution of gas was fairly uni-

Jan 1, 1930

By H. J. Rose

In a paper1 presented before this Institute in 1926,I briefly discussed the evaluation of coking coals by means of ultimate analysis. The paper contained several graphic studies in which coal analyses calculated free of moisture, ash, sulfur and nitrogen were plotted on triaxial diagrams in which carbon + hydrogen + oxygen = 100 per cent. From a study of such data for 600 coking coals of the United States, and 150 coking coals of Wales, France and Germany, it was concluded that it was usually possible to predict coking properties and by-product yields with fair success from ultimate analysis. The coals which have proved exceptions to the general rules were found to have physical peculiarities. Run-of-mine Coal It must not be forgotten that run-of-mine coal is a composite material consisting of many constituents differing in physical properties and chemical analysis. A coal sample usually contains: 1. Glossy black coal known as anthraxylon or vitrain. This constituent usually has the strongest coking properties, and the lowest ash content. 2. Dull black coal consisting of attritus containing thin layers of anthraxylon. It is also known as clarain. This constituent, in a coking coal, usually has good to excellent coking properties. 3. Mineral charcoal or fusain. This is a porous black material which is soft and crumbly (unless impregnated with mineral matter) and which has absolutely no coking properties. It is different in every respect from the other constituents in coal. The volatile matter content of mineral charcoal is less than 20 per cent. even when it is associated with high-volatile coals. As would be expected the hydrogen content is low, and the carbon content is high. 4. A coal sample may contain tough gray canneloid material which has a high-volatile matter and a high hydrogen content, but is poor in coking qualities.

Jan 1, 1930

By D. K. Crampton

INTERNAL stress and season cracking in brass have been studied for many years and the technical literature contains many data on various phases of the subject. A résumé of the literature shows certain fairly well established points upon which various authors are mostly agreed: 1. Season cracking is primarily caused by the presence of relatively high internal stresses, or possibly in some cases by external stresses, or both. 2. A specific corrosion is also essential to season cracking: Certain agents, particularly mercurous salts, mercuric salts and ammonia salts; have such a specific corrosive effect. 3. The tendency to season crack under given conditions increases with increasing zinc content, brass containing less than 20 per cent zinc being relatively immune. 4. In alpha brass the season cracks are intercrystalline; in alphabeta brass they lie between the two constituents; and in beta brass they are transcrystalline. 5. The ordinary impurities or added elements in special brasses have little or no effect on the tendency to season crack. 6. Internal stresses can be eliminated, or at least reduced to a safe 'limit by annealing treatments at temperatures that do not produce visible microstructural changes or appreciable softening of the worked brasses. There are, however, some points in connection with the phenomenon of season cracking which have not been thoroughly investigated, or wherein different authors and investigators are not entirely in agreement. The investigations described in this paper were undertaken to determine: 1. The correlation between mercurous nitrate tests and actual season cracking on long-time atmospheric exposure. 2. The quantitative effect of type and degree of drawing operations on the intensity of internal stress and on the tendency to season crack in brass tubes. 3. The possibility of drawing high-brass tubes in such a manner as to prevent the occurrence of harmful stresses rather than to find a remedy for such stresses once having obtained them.

Jan 1, 1930

By Stanley C. Herold

Only two years ago there appeared in our technical magazines articles wherein it was shown that the application of back-pressure increased the ultimate production of a well, that edge water can be stopped in its encroachment by the injection of gas into the productive formation, with the consequent conservation of energy within the pool, that gas is the source of all energy involved in oil production, and that each pool has a definite minimum-valued gas-oil ratio to be attained for the most economical operation of wells. Today we are not so certain of these matters. Probably in some fields, under special circumstances, these ideas are correct, but certainly they must not be correct in all fields, under any and all circumstances. The nature of the productive structure, the location of particular properties on the structure, the existence of adjoining neighbors, whether these are higher or lower on the structure, and the methods of production followed by all operators on the structure, sand for sand on depth, make these subjects worthy of full consideration. Our difficulties in analyzing and comparing the performance of reservoirs in various parts of the world do not rest solely upon structural features and property lines. We do not complete the list of causes for these difficulties if we add lithologic features and correlation of strata encountered by the drill, with the magnitude of pressures exerted by fluids within any of these strata. A further cause, one which the author believes will complete the list, is one involving the theoretical mechanics of fluids within porous formations—porous in the nature of interstices in sandstones and some limestones, networks of fractures in shales, and cavities in otherwise compact limestones. The confusion of ideas concerning reservoir mechanics still with us today seems largely due to our failure to recognize among all wells three great divisions of theoretical mechanics, three great systems which are distinct in themselves, and according to which each well, or better, each group of wells, must be analyzed separately. These systems have been named by the writer Hydraulic Control, Volumetric Control and Capillary Control, respectively.' Wells in these controls behave dif-

Jan 1, 1930