122. The Resolving Power of Objectives. ...P. G. Nutting A half-tone screen illuminated with monochromatic light as test object gave a simple and sensitive means of testing the well-known formula for resolving power. Different values of the resolving power constant were interpreted in terms of quality of image. The performance of telescope and camera objectives was compared as regards resolving power and residual axial aberrations. (Aug., 1909.) 5 PP. 131. Selective Radiation from Various Solids. II. ... ....W. W. Coblentz The present paper is a continuation of previous work (No. 97) on this subject. Several minerals are shown to be solid solutions instead of definite chemical compounds, which suggests that this method of analysis might be of use in studying the physical condition of highly fusible oxides. The spectral energy curves of carbon and tungsten are set to a "color match" and it is shown that the eye is incapable of detecting a difference in emissivity of 5 per cent or more in the extreme red end of the spectrum. (Aug. 14, 1909.) 18 pp. 132. Luminous Efficiency of the Firefly..Herbert E. Ives and W. W. Coblentz For the purpose of obtaining the spectral energy distribution of the firefly light, photographs were taken of the spectrum of the species "Photinus pyralis" and also of the carbon glow lamp. The densities of the negatives were measured, and the spectrophotometric curve of the firefly light thereby obtained was compared with that of carbon lamp. The spectral energy curve of the carbon lamp was determined by radiometric methods and, by means of the ratios of the spectrophotometric intensities of the firefly light to the glow lamp, the spectral energy curve of the firefly was obtained. The luminous efficiency of the firefly and glow lamp were obtained from the spectral energy curves. The glow lamp (4 watt) proved to have 0.4 per cent efficiency, the firefly 96.5 per cent. (Aug. 1, 1909.) 15 PP. 133. Luminosity and Temperature. P. G. Nutting Making use of the luminosity function developed in a previous paper, the complete expressions for luminosity and luminous efficiency of bodies of known temperatures is worked out. In conclusion, numerical values are calculated in candles per watt for various lamps and other bodies and the results found to be in close agreement with known data. (July, 1909.) 9 pp. 142. A Modified Method for the Determination of Relative Wave-Lengths... .Irwin G. Priest A method especially adapted to the establishment of secondary standards. Characteristics of the Method: (1) Use of circular interference fringes. (2) Use of the double increment in the distance between two mirrors as difference of path. (3) Use of method of flexure to measure "fractions. Accuracy attained: (1) Average residual (7 determinations) I part in 8 400 000. (2) Maxi- Advantages of Method: (1) Rigorous control of errors. (2) Small chance of apparatus and (4) Automatic elimination of temperature error without thermostat. (5) Automatic elimination of error of "dispersion of phase." (June, 1910.) 34 PP. 146. The Intensities of Some Hydrogen, Argon, and Helium Lines in Relation to Current and Pressure. .P. G. Nutting and Orin Tugman The intensities of spectrum lines are known to vary widely with the condition of the gas or vapor emitting them. This paper contains the results of a study of the visible spectra of hydrogen, argon, and helium contained in Plucker tubes. The curves given show the variations in the intensities of about 20 lines with varying current and gas density. Potential gradient as a function of current was determined for hydrogen and helium, so that for these gases line intensity is known as a function of the internal energy of the gas. Finally a summary of the important new results are given. (Aug. 6, 1910.) 22 pp. 150. Note on Oscillatory Interference Bands and Some of Their Practical Applications... (Sept. 1, 1910.) 12 pp. 152. The Reflecting Power of Various Metals. G. O. Squier and A. C. Crehore .W. W. Coblentz This paper gives an illustrated description of an investigation of the reflecting power of various pure metals, including tungsten, molybdenum, tantalum, graphite, antimony, silicon, chromium, etc. The results obtained give additional evidence to previous observations, showing that a common property of pure metals is a low reflectivity in the visible spectrum and explains the high luminous efficiency of the tungsten and other metal filament lamps. Several supplementary notes are added in which are given the thermoelectric power of molybdenum-copper, comments on the radiation laws of metals, etc. (Dec. 6, 1911.) 53 pp. 154. The Visibility of Radiation. A Recalculation of König's Data... .P. G. Nutting This is a supplementary note and correction to the previous paper on the Luminous Equivalent of Radiation. From the paper reprinted in his works, it appears that König's data on Equivalent Slit Widths had not been corrected for variable prismatic dispersion. This dispersion is given in a later paper and is now applied to correct the visibility curves so much used in spectrophotometry and in problems in illumination. The most notable effect of the correction is the shift of the maximum at high intensities from 565 back to 544. (Oct. 1, 1910.) 4 pp. 155. A Photometric Attachment for Spectroscopes... ....P. G. Nutting For simplicity and convenience the polarization spectrophotometers are far ahead of other types, but have lacked sensibility and precision. In the new form an image of the finely ruled dividing surface is thrown on the slit of any spectroscope (wave length, high intensity, high dispersion). Tests of an instrument show that it has the highest sensibility of which the eye is capable, good light, economy, and, of course the dispersion of any spectroscope to which it is attached. The scale correction is shown to be negligible by three different tests. (Oct. 1, 1910.) 3 pp. 156. Selective Radiation from Various Substances. III....W. W. Coblentz An investigation of the emission and the absorption of the acetylene flame and the Welsbach mantle. The acetylene flame has an absorption band in the orange yellow, with regions of greater transparency in the violet and in the red. It is shown that the spectral energy curves of the Welsbach mantle and of the same material used as a solid electrically heated glower are entirely different, due to the great difference in the thickness of the radiating layer. Further experiments are described on the question of color match versus spectral intensity match, showing that the superposition of the spectral energy curves of two widely different sources of radiation holds true over only a very short spectral region. (Nov. 9, 1910.) 52 pp. 168. Radiometric Investigation of Water of Crystallization, Light Filters, and Standard Absorption Bands....W. W. Coblentz The present paper contains further contributions (see No. 45) to the question of the manner in which water is contained in minerals. A detailed examination was made of the absorption spectra of opal and tremolite in various states of dehydration. The former shows the absorption bands of water, while the latter does not, although it is supposed to contain dissolved water. The radiometric test finds no distinction between "water of crystallization," "dissolved water," "absorbed water," and water in "solid solution,' all of which give absorption bands identical with those of water in its free liquid state. Minerals containing "water of constitution" do not show the absorption bands of water. The paper contains also the transmission and reflection spectra of a miscellaneous collection of substances, including sylvite and quartz glass. On "light filters" it is shown that a 2-cm thickness of a 2 per cent solution of cupric chloride absorbs all the infra-red beyond 0.67 μ and transmits 80 per cent in the green and blue. Standard spectral lines are given for calibrating prisms. (May 16, 1911.) 45 PP. 176. The Luminous Properties of Electrically Conducting Helium Gas. II. Reproducibility. . . ..P. G. Nutting This paper gives the results of photometric and spectrophotometric tests of a set of 38 helium tubes made up and operated as shown most advisable by preliminary work. The tubes do not differ measurably in color. In light emission per cm of capillary the average deviation is 1.15 per cent, the maximum deviation 3 per cent, the uncertainty in observation being 1 per cent. (Aug. 25, 1911.) 8 pp. 179. Wave Lengths of Neon.. ..I. G. Priest Ten wave lengths resulting from determinations by the method described in Reprint 142, Bulletin of the Bureau of Standards, are presented in a table. The precision, reliability, and accuracy of these values are discussed. The probable errors are all less than one part in 10 ooo ooo, and the values are considered accurate to within about one or two parts in 6 000 000. (Nov. 23, 1911.) 6 pp. See also (on p. 43) Circulars 12, 27, and 28. V. CHEMISTRY 53. On the Colorimetric Determination of Iron with Special Reference to Chemical Reagents. . . . .H. N. Stokes and J. R. Cain A method of separating iron from materials in which it exists in minute traces and of determining it colorimetrically as sulphocyanide. (Jan. 20, 1907.) 42 pp. 54. On Sulphocyanic Acid.. .H. N. Stokes and J. R. Cain An improved method of preparing sulphocyanic acid, especially for colorimetric iron determinations, with observations on its properties and those of some of its derivatives. (Jan. 20, 1907.) 5 PP. 77. The Atomic Weight of Hydrogen.. W. A. Noyes A determination of the ratio of hydrogen to oxygen by direct synthesis of water by the action of hydrogen on copper oxide and by the union of hydrogen and oxygen over palladium foil. (Sept. 11, 1907.) 26 pp. 81. The Atomic Weight of Chlorine.......W. A. Noyes and H. C. P. Weber A determination of the atomic weight of chlorine by the direct synthesis of hydrochloric acid by means of hydrogen and potassium chloroplatinate. (Oct. 1, 1907.) 20 pp. 82. The Preparation of Chloroplatinic Acid by Electrolysis of Platinum Black... .H. C. P. Weber A method of preparing chloroplatinic acid free from nitric acid by the electrolysis of finely divided platinum in concentrated hydrochloric acid. (Oct. 8, 1907.) 3 pp. 153. The Action of Sunlight and Air upon Some Lubricating Oils.. ...C. E. Waters By the combined action of sunlight and air certain lubricating oils were found to yield a solid oxidation product within six hours, the amount increasing at a slowly diminishing rate, but not ceasing after four months' continual exposure. The oils gained in weight in spite of the water and carbon dioxide, as well as traces of volatile oily matter, that were given off. The increase in the acidity of the oils was also determined. The oil filtered from the oxidation product was found to contain considerable oxygen. (Sept. 29, 1910.) 8 pp. 160. The Behavior of High-Boiling Mineral Oils on Heating in the Air.... ..C. E. Waters Results of "carbonization" tests of gas-engine oils when heated in flasks; also when heated in tubes of glass, brass, cast iron, and different steels. The tests made in tubes show some evidence of catalytic effects and indicate possible variations due to fatty oil, a question which will be taken up in the near future. (Dec. 14, 1910.) 12 pp. 161. The Determination of Vanadium in Vanadium and Chrome Vanadium Steels.... J. R. Cain Errors in the usual methods for determining vanadium in steels are considered and methods of eliminating or correcting for some of these are discussed. A new method, based on precipitation of the vanadium by cadmium carbonate, followed by electrolysis, reduction, and titration, is described. (Apr. 24, 1911.) 16 pp. 174. The Determination of Total Sulphur in India Rubber..... ..C. E. Waters and J. B. Tuttle Comparative determinations by different methods, especially a number of variations of the method of Henriques. These determinations were made on rubber and also on a sample of very dilute sulphuric acid. The amount of error caused by the presence of lead sulphate was also determined. The method adopted and used for some time in our routine work is a modification of that of Henriques. The rubber is attacked by nitric acid saturated with bromine, instead of using nitric acid alone. (July 19, 1911.) 9 PP. 178. The Hydrolysis of Sodium Oxalate and Its Influence Upon the Test for Neutrality ..William Blum In connection with the testing of sodium oxalate for use as a primary standard for acidimetry and oxidimetry, a knowlegde of the normal alkalinity of the pure salt is important. The purest sodium oxalate that could be made was found to produce in o. 1 molar solution a pink color with phenolphthalein, equivalent to 4 per cent transformation of the indicator, and 6 per cent in 0.2 molar solution. This value was not in accord with that calcu lated from the theory of hydrolysis, using the present accepted values for the various constants. The error produced by neglecting this alkalinity in determinations of the purity of the salt was found to equal about 0.02 per cent, which is negligible for practical purposes. The action of sodium oxalate solution on various kinds of glass, and the behavior of such solutions on heating, was also studied. A method for the accurate testing of the neutrality of sodium oxalate is described. (Nov. 9, 1911.) 20 pp. The Standardization of Potassium Permanganate Solution by Sodium Oxalate. R. S. McBride The effect of temperature, acidity, volume of solution, rate of titration, access of air, and presence of added manganous sulphate upon the value obtained for a permanganate standardized against sodium oxalate was determined and the necessary end-point corrections fixed. Loss of oxygen during titration is probably responsible for the observed variations, but none of these exceed one-half per cent. The following procedure is recommended: Dissolve 0.25-0.3 g of sodium oxalate in 200-250 cc of 5 per cent (by Vol.) sulphuric acid 80-90°, and titrate at once, stirring the solution vigorously and continuously. The main part of the permanganate should be added not more rapidly than 10-15 cc per minute, and the last 1⁄2-1 cc dropwise. A correction for the amount of permanganate necessary to produce the end point is desirable. See also (on p. 43) Circulars 14, 19, 25, and 26. (E) DESCRIPTIVE LIST OF TECHNOLOGIC PAPERS 1. Effect of Preliminary Heat Treatment upon the Drying of Clays.... .A. V. Bleininger 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. 2. 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 per cent 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 is 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. 3. Tests of the Absorptive and Permeable Properties of Portland Cement Mortars and Concretes, Together with Tests of Damp-proofing and Water-proofing Compounds and Materials... .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 "water-proofing" 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 dampproofing or water-proofing 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. 4. The Effect of Added Fatty and other Oils upon the Car bonization of Mineral Lubricating Oils... .......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 also caused an increase. 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. |