S423. Operation of the Modulator Tube in Radio Telephone Sets.. .E. S. Purington ... The modulating device in radio communication varies the output current of a radio generator at a frequency lower than the radio frequency. This paper deals with the phenomena of modulation by speech in radio telephone transmitting sets employing electron tubes. A radio telephone transmitter is analyzed into four units-power supply, modulator unit, the generator unit, and the radiator unit. The essential operation and the limitations of the modulator unit are discussed. The strength of speech signals and power rating of radio telephone sets are discussed. (Nov. 15, 1921.) 30 pp. Price, 10 cents. S424. Mathematical Theory of Induced Voltage in the Three different circuits representing in simplified form the essential features of the high-tension magneto are developed and equations for the electrical performance of each are given. It is shown that by the insertion of proper electrical constants in these equations the resulting performance will be substantially the same as that of an actual magneto. Methods are suggested for the experimental determination of these constants and the agreement between this theory and observed results as shown in certain cases. (Dec. 13, 1921.) 63 pp. Price, 15 cents. $425. Characteristic Soft X-Rays From Arcs in Gases ..F. L. Mohler and Paul D. Foote and Vapors.. Critical radiating potentials for II gases and vapors have been measured in a range from 17 to 500 volts. The spectrum range of limiting frequencies is from λ=700 to λ=25A. The principal L series limits for sodium, magnesium, phosphorus, sulphur, and chlorine have been measured. A new softer L series for these elements is also indicated by the results. The K limits for carbon, nitrogen, and oxygen and the M limits for potassium have been measured. Experiments on radiation from solids indicate that nearly pure characteristic effects with no measurable general radiation can be obtained under the best vacuum conditions. Results with nickel show radiation starting at 80 volts. (Dec. 17, 1921.) 26 pp. Price, 10 cents. S426. Thermal Expansion of Nickel, Monel Metal, .Wilmer H. Souder and Peter Hidnert This paper gives data on the thermal expansion of 29 samples of commercial nickel, monel metal, stellite, stainless steel, and aluminum, and results obtained by previous observers on the expansion of nickel and aluminum. All of these materials except stainless steel (heated to 900° C) were examined from room temperature to about 600° C. The results are presented in the form of tables and curves. The expansion curves of stellite show irregularities in the region between 300° and 500° C. For commercial nickel only a slight irregularity was perceptible at about 350° C. For the range from room temperature to 100° C, the coefficients of expansion vary from 9.6×1076 for a sample of hardened stainless steel to 23.8× 10TM for a sample of exceptionally pure aluminum. (Dec. 17, 1921.) 23 pp. Price, 10 cents. 90308-22-6 S427. Some Effects of the Distributed Capacity between Inductance Coils and the Ground.......Gregory Breit When two condensers connected in series with common terminal grounded are connected across the terminals of an inductance coil as in the figure, their effective capacity in series is not equal to their effective capacity so far as resonance of the coil is concerned. If the capacity of one condenser CC is the effective capacity of the is C, and of the other C2, the quantity 1 C2+C2 two condensers in series. As stated, it does not stay constant when C, is changed arbitrarily and C, is readjusted for resonance. A mathematical calculation shows, however, that provided the coil is symmetrical with respect to its two terminals the quantity is linearly related to Experimental verification of this fact has been obtained. (Dec. 21, 1921.) 7 pp. Price, 5 cents. S428. The Radio Direction Finder and Its Application to I C1+C2* .Frederick A. Kolster and Francis W. Dunmore The development of the radio direction finder, together with the radio fog-signaling system, has been undertaken by the Bureau of Standards, and in cooperation with the Bureau of Lighthouses extensive practical tests have been conducted. The radio direction finder as a nautical instrument is completely described, and the results of experiments are given. Three radio-signaling stations or radio beacons have been established at the entrance to New York. During fog, or at such times as may be necessary, these stations transmit their characteristic signals at frequent intervals. Ships equipped with radio direction finders can at such times take bearings on these stations and thereby proceed with safety. The application of the direction finder to navigation and the establishment of fog-signaling stations at lighthouses and on board light vessels will result in more adequate protection to life and property at sea. (Jan. 16, 1922.) 38 pp. Price, 15 cents. $429. Note on the Preparation of Mannose. . .... .E. P. Clark A method is described by which mannose may be prepared easily and economically. Ivory-nut shavings or sawdust are treated with dilute NaOH, washed, and dried. 500 grams of the material thus prepared are digested for a day with 75 per cent sulphuric acid, then dissolved in water to make 5.5 liters. This mixture is boiled for 21⁄2 hours, neutralized with BaCO3, concentrated, and the sugar crystallized from glacial acetic acid, giving a yield of 42 to 45 per cent of the treated meal. (Jan. 16, 1922.) 2 pp. Price, 5 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.] ...A. V. Bleininger TI. Effect of Preliminary Heat Treatment upon the Drying 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 oil, 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 .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 modulus 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 compressive 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 determination, 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. (Nov. 1, 1911.) 6 pp. Price, 5 cents.) T7. The Testing of Clay Refractories, With Special Reference to Their Load Carrying Ability at Furnace Temperatures. ...A. V. Bleininger and G. H. Brown NATURE OF TESTS.-General consideration of the refractoriness of fireclay bricks, their viscosity at furnace temperatures, nature and manufacture of refractory clays, effect of accessory constituents upon softening temperatures, effect of fluxes upon refractoriness, effect of heat upon dehydration, contraction, crystallization, and load carrying capacities. I RESULTS.-General conclusions are stated and specifications proposed for No. 1 and No. 2 refractories. (Dec. 15, 1911.) 78 pp. Price, 15 cents. T8. A Rapid Method for the Determination of Vanadium in Steels, Ores, etc., Based on Its Quantita- .J. R. Cain and J. C. Hostetter Vanadic acid may be precipitated quantitatively by ammonium phosphomolybdate. The vanadium may be separated from the precipitate, or it can be accurately determined in it by reduction and titration with permanganate. (Oct. 26, 1911.) 20 pp. Price, 5 cents. 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, ro 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. J. 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. |