S502. An Improved Type of Wave Meter Resonance Indicator ....Morris S. Strock Most portable wave meters use, as a resonance indicator, a thermogalvanometer connected in the tuned circuit. This increases the resistance of the wave-meter circuit and gives comparatively small resonance deflections at low settings of the wave-meter condenser. As a result, the precision of setting the wave-meter condenser is reduced. This paper describes a resonance indicator for a portable wave meter which can be used in place of the thermogalvanometer. It gives an approximately uniform resonance deflection over the frequency range of the wave meter, does not appreciably increase its resistance, and is more sensitive than the thermogalvanometer. Experimental data are given to show that this method of resonance indication permits of precise settings of the wave-meter condenser. The resonance indicator may be added to most portable wave-meters and results in greater precision in their use. (Mar. 6, 1925.) 8 pp. Price, 5 cents. S503. A Flow Calorimeter for Specific Heats of Gases N. S. Osborne, H. F. Stimson, and T. S. Sligh, jr. The flow calorimeter described in this paper has been designed and built primarily for determining the specific heat of superheated ammonia vapor at constant pressure. The aim has been to develop an instrument for accurate measurement of the specific heat of gases at pressures below 100 atmospheres and temperatures below 150° C. Refinements have been incorporated into the apparatus to make it sensitive, responsive, and to avoid thermal leakage, to control experimental conditions which affect steadiness, and to keep the size of the instrument within limits appropriate for small samples of pure materials. The instrument has been used successfully to obtain data, in the superheat field of ammonia, which have been used in preparing tables of the thermodynamic properties of this refrigerating agent. (Apr. 4, 1925.) 33 Pp. Price, 20 cents. S504. A Method of Studying Electrode Potentials and ....Homer D. Holler A resistance-coupled electron tube amplifier was used to operate an oscillograph for observing and recording the variations in potential of several electrodes without requiring any current from the electrode under investigation. By superposing alternating current upon the electrode it was possible with the use of a separately excited wattmeter to measure the potential due to resistance and compute the boundary resistance at the electrode. The paper is limited to a description of the method and illustrations of its use in the case of some typical electrodes, including both smooth and platinized platinum, carbon, lead, and copper in sulphuric acid, and copper in a copper sulphate solution. (Apr. 17, 1925.) 14 PP. Price, 15 cents. S505. Critical Potentials Associated with Excitation of .F. L. Mohler The experimental results include electrical measurements of critical potentials and a spectroscopic study of conditions for exciting alkali spark spectra. Data on all the alkali metals are given. It is found that the potential required to excite spark lines in the thermionic discharge depends on the current density, being from 8 to 12 volts higher for small currents than for large currents. The lower potential measures the work required to remove one electron from the rare gas shell of the atom while the higher value gives the work required to doubly ionize the atom by a single collision. (Apr. 16, 1925.) 25 Pp. Price, 10 cents. S506. Theory and Interpretation of Experiments on the Walls... ..Edgar Buckingham As a preliminary, the principles brought out by W. C. Sabine's work on the reverberation of closed rooms are discussed, and the equations needed for interpreting the observed facts are deduced for further reference. The theory of reverberation suggests experimental methods for measuring the acoustic transmittance of panels by means of observations in two closed rooms which are in acoustic communication only through the panel, which is set up as a part of the partition wall between the rooms. The necessary equations are developed for interpreting such experiments and expressing the results in absolute units, so as to give values which are characteristic of the panel alone and independent of the peculiarities of the laboratory where the tests are conducted. The proposed methods are then compared with those employed by Paul E. Sabine and F. R. Watson and it is shown that the quantities measured by the different methods are not physically identical, hence discrepancies are to be expected among the values obtained, although it seems probable that all the methods would arrange any given set of panels in the same order. (May 26, 1925.) 27 pp. Price, IO cents. $507. A New Interference Apparatus for Testing Haemacytometers.... ..C. G. Peters and B. L. Page Haemacytometers or counting chambers, used in determining the number of corpuscles in the blood, were previously tested with a micrometric instrument, which was subject to imperfections that produced appreciable errors in the measurements. A new instrument, based on the principle of the interference of light waves, which is free from instrumental errors and with which a chamber can be measured in one minute with an uncertainty of not more than o. 1 micron was, therefore, designed and constructed. A description of the new apparatus and the results of comparative tests of the accuracy and reliability of both instruments are presented in this paper. (June 3, 1925.) 16 pp. Price, 10 cents. S508. Spark Photography and Its Application to Some Problems in Ballistics.. ..Philip P. Quayle Apparatus for securing shadowgraph pictures by spark illumination of extremely short duration is described. The application to the study of projectiles in flight both near to and remote from the firing piece is discussed and numerous photographs are presented giving evidence as to the acceleration of a projectile outside the piece and on other physical phenomena. The object of the photographs is to illustrate the effectiveness of the method rather than to present an exhaustive study of the subjects tcz. which they relate. (June 13, 1925.) 40 pp. Price, 20 cents. TECHNOLOGIC PAPERS [For publications in following list that are out of print or procurable only from Superintendent of Documents, Government Printing Office, Washington, D. C., see the supplement to this Circular.] TI. Effect of Preliminary Heat Treatment upon the Dry ..A. V. Bleininger ing of Clays.. Investigation undertaken to ascertain the possibility of using excessively plastic clays which on drying show losses due to cracking and checking, by subjecting the clays in the crude state to a preliminary heat treatment before working them by the usual methods. Preheating offers a possible commercial method for the treatment of excessively plastic clays which can not be worked and dried successively by other means, subject to certain limitations. Methods and conditions are discussed. (Dec. 6, 1910.) 53 pp. Price, 10 cents. T2. The Strength of Reinforced Concrete Beams-Results of Tests of 333 Beams (First Series) .. .Richard L. Humphrey and Louis H. Losse NATURE OF TESTS.-These tests form a part of the study of the behavior of reinforced concrete beams under load. This series consisted of tests of gravel, granite, limestone, and cinder concrete, with seven percentages of reinforcement varying from 0.5 to 2 per cent. Beams were accompanied by cylindrical and cubical test pieces for determining compressive strength, initial modulus of elasticity, yield point, bond, etc. METHODS.-The beams were 8 by 11 inches in section and 13 feet long, tested on 12-foot centers by applying loads at the third points. Observations were made of deformation of upper and lower fibers, deflection of beam at the center, slip of the reinforcement, and development of cracks as the loads were applied. RESULTS.-Complete data are given of the beam tests, results are summarized and illustrated by typical curves, diagrams, and photographs, and studies are made of the values usually used in the design of a beam. (June 27, 1911.) 200 pp. Price, 50 cents. T3. Tests of the Absorptive and Permeable Properties of .Rudolph J. Wig and P. H. Bates NATURE OF TESTS.-Results of tests of the absorption of water and permeability to water of Portland cement mortars and concretes, together with tests of 40 commercial so-called “damp-proofing" and "waterproofing" compounds. METHODS.-Tests were made by exposing one surface of small slabs to water, both permitting absorption by capillarity and subjecting one surface to hydrostatic pressure, measuring the quantity of water passing through. RESULTS. None of the integral compounds was found to be of much value as damp-proofing or waterproofing mediums nor in reducing the absorption. Well-made Portland cement mortar and concrete were found to be impermeable to the passage of a sensible quantity of water under hydrostatic pressures of 20 pounds per square inch, and rich mortars if aged sufficiently will be impermeable to 60 and 80 pounds per square inch hydrostatic pressure. (Aug. 22, 1911.) 127 PP. Price, 20 cents. T4. The Effect of Added Fatty and Other Oils Upon the .C. E. Waters Continuation of work published in Bul. 7, p. 365 (1911). Known mixtures of mineral oil with fatty oils, etc., subjected to the carbonization test. The amount of insoluble precipitate is variously affected. Rosin, asphalt, etc., caused an increase; rosin on, lard oil, rapeseed oil, and tallow caused a decrease. Oil exposed to the oxidizing action of sunlight and air, and oil mixed with ferric oxide yielded more of the carbonized product. The addition of fatty oils is not yet recommended. More work is to be done with a view to determine the corrosive action on metals. (Aug. 24, 1911.) 14 pp. Price, 5 cents. T5. The Effect of High-Pressure Steam on the Crushing Concrete. Rudolph J. Wig NATURE OF TESTS.-Results of tests made to determine the accelerating action of steam on the hardening of Portland cement mortar and concrete. Tests were made varying the steam pressure, duration of exposure, age and consistency of mixtures, etc. METHOD. Cylindrical test pieces 8 inches in diameter by 16 inches in length were exposed in a steel tank equipped with removable head, steel cars, and track, and provided with regulating valves for controlling steam pressure. The ultimate compressive strength, initial nodulus of elasticity, and yield point were then determined. RESULTS. Steam under pressure greatly accelerated the hardening of the mortar and concrete. Under certain conditions, a comp Bressive strength was obtained greatly in excess of that obtained by aging normally for one year. (Sept. 5, 1911.) 25 pp. Price, 10 cents. T6. The Determination of Chromium and Its Separation From Vanadium, In Steels.. J. R. Cain Sources of error in certain methods used for this determina tion, which limit their accuracy, are described. A procedure is given for the quantitative precipitation of chromium (and of vanadium) from solutions of steels (permitting a separation from most of the iron), for its separation from this precipitate in pure condition and for its determination." 1, 1911.) 6 pp. Price, 5 cents. T7. The Testing of Clay Refractories, With Special Reference to Their Load Carrying Ability at Furnace Temperatures... I (Nov. ....A. V. Bleininger and G. H. Brown NATURE OF TESTS.-General consideration of the refractoriness of fire clay bricks, their viscosity at furnace temperatures, nature and manufac ture of refractory clays, effect of accessory constituents upon softening g temperatures, effect of fluxes upon refractoriness, effect of heat upon dehy dration, contraction, crystallization, and load carrying capacities. RESULTS.-General conclusions are stated and specifications propose for No. 1 and No. 2 refractories. (Dec. 15, 1911.) 78 pp. Price, 15 cent T8. A Rapid Method for the Determination of Vanadium in Steels, Ores, etc., Based on Its Quantitative Inclusion by the Phosphomolybdate Precipitate.. ..J. R. Cain and J. C. Hostet Vanadic acid may be precipitated quantitatively by ammonium p' phomolybdate. The vanadium may be separated from the precipit or it can be accurately determined in it by reduction and titration d S. T9. The Density and Thermal Expansion of Linseed Oil and Turpentine.. .....H. W. Bearce The paper describes an experimental determination of the density and thermal expansion of linseed oil and turpentine. The work was undertaken for the purpose of obtaining the necessary data for preparing tables to give the density of these substances at any temperature between 10° and 40° C, from the density at any other temperature. The data obtained are herein presented, together with the tables prepared therefrom. There are included also tables for converting pounds to gallons and gallons to pounds. (Apr. 15, 1912.) 27 pp. Price, 10 cents. Tio. The Melting Points of Fire Brick. ..C. W. Kanolt Determinations have been made of the melting points of 62 samples of fire brick and of material of importance in the manufacture of fire brick. These samples included fire-clay brick, bauxite brick, silica brick, magnesia brick, chromite brick, kaolin, pure alumina, pure silica, bauxite, bauxite clay, and chromite. The materials were heated in an electric vacuum furnace. Temperatures were measured with an optical pyrometer. An improved method of calibrating optical pyrometers is described. (June 15, 1912.) 17 pp. Price, 5 cents. TII. Comparison of Five Methods Used to Measure Ralph P. Devries The static tests of hardness studied are the cone and Brinell sphere. The dynamic tests are the Shore Scleroscope and Ballantine. The Bauer drill test for measuring the workability of metals is also included. The tests were made on a series of metals which ranged from very hard steels to comparatively soft alloys. The laws governing the resistance to indentation are experimentally deduced for spheres of different sizes and cones of different degrees of angular opening. The effect of elastic deformation of the sphere upon the results of sphere tests is determined by means of a method which involves the exact measurement of the depth of indentation. This method of measurement is also applied to the cone tests. The study of the individual methods shows (1) the possibility of obtaining rational hardness numerals for the cone and sphere tests, and (2) that the dynamic tests for hardness do not agree in general with the results of static tests. (July 22, 1912.) 27 pp. Price, 5 cents. T12. Action of the Salts in Alkali Water and Sea Water ..... .P. H. Bates, A. J. Phillips, and Rudolph J. Wig NATURE OF TESTS.—A series of laboratory and field investigations made to determine the suitability and permanency of various cements in structures exposed to the chemical and mechanical action of the salts present in sea water and alkali water. METHODS. The laboratory investigation consisted in subjecting various typical cements to salt solutions for a period of months and their action noted by analyzing the solutions as removed and the residue at the end of the test. Small hollow cylinders of cement and cement mortar were made and exposed to the percolation of various salt solutions. Field investigations were made by exposing cements in the form of briquets and concrete test pieces to sea water at a branch laboratory established at Atlantic City, N. Į. RESULTS.-Tentative conclusions are drawn showing that concrete is subject to disintegration by the mechanical force exerted by the crystallization of salt in its pores if sufficient quantity is permitted to accumulate; that there is no relation between the chemical composition of a cement and the rapidity with which it reacts with sea water when brought into intimate contact; and that marine construction appears to be a problem of method rather than materials, as concrete sets and permanently hardens as satisfactorily in sea water as in fresh water or in the atmosphere, if it can be placed in the forms without undue exposure to the sea water while being deposited. (Nov. 1, 1912.) 157 PP. Price, 25 cents. |