Showing papers in "Journal of The Franklin Institute-engineering and Applied Mathematics in 1917"

The vertical distribution of dissolved oxygen and the precipitation by salt water in certain tidal areas

Abstract: It has been shown that the lower layers of certain tidal waters under investigation contain less dissolved oxygen than the upper layers. Evidence has been presented to show that this phenomenon is caused by the stratification of the water due to the specific gravity of the under-run of sea-water, which cuts off vertical circulation, and to the subsequent depletion of the oxygen in the lower layers by natural agencies. The depletion of oxygen was found to be greatest in September. The precipitation and sedimentation of matter in tidal areas by sea-water have been presented in graphic form. These data are considered to be of particular interest from the viewpoint of fish and shellfish life.

The formation of crystals in gels

Abstract: 1. 1. Good crystals of silver dichromate were obtained by allowing the slow diffusion of solutions of silver nitrate and potassium dichromate through flowers of sulphur. Barium sulphate powder served as well, and alundum was even better. This coil-firms Dreaper's opinion that diffusion through capillary spaces other than those in a gel may be efficient ill aiding crystal formation. 2. 2. An experiment was devised to prove that in many instances the amorphous or fine-grained precipitate formed when two solutions meet acts as a. nlembrane or network of capillaries. retarding further diffusion and favoring the formation of more of the precipitate in larger crystalline particles. 3. 3. Silicic acid gels of alkaline reaction were made by mixing sodium silicate with less than enough acid for neutralization. These basic gels made possible the production of crystalline salts not possible in a gel of acid reaction. 4. 4. Cold in a beautifully crystalline condition was best prepared by mixing equal volumes of a water-glass, 1.06 density, and 3 N sulphuric acid, adding 1 c.c. of 1 per cent. chloride to 25 c.c. of the mixture and, after solidification of the gel, covering with a solution of 8 per cent. oxalic acid. Startling rainbow bands of red, blue, and green colloidal gold. mixed with scattered crystals, resulted when the water-glass was 1.16 density. Both methods worked readily and gave better results than any yet recorded. 5. 5. Perfect tetrahedrons of copper were secured by using 1 per cent. hydroxylamine hydrochloride to reduce dilute copper sulphate in a silicic acid gel. Peculiar aggregates of tetrahedrons similar to those found in copper deposits in Xature were also observed. All the steps of the reduction of cupric hydroxide to yellow and red forms of cuprous oxide were shown simultaneously in a series of many bands, using glucose as the reducing agent in a silicic acid gel of alkaline reaction. With 1 per cent. hydroxylamine the same reduction was carried through the cupric hydroxide and cuprous oxide to tetrahedrons of metallic copper. This suggests a method of controlling the different steps of other reactions for study. 6. 6. Lead iodide in perfect hexagonal plates, 5 mm. wide, and golden, fern-like growths, 8 cm. long, were formed in silicic acid gels. A basic lead iodide in yellow-white needles, 2 cm. long, formed by the action of excess lead acetate on potassium iodide in a slightly acid gel and even better in a slightly basic gel. Iodine was released on the surface of crystals of lead iodide, as shown by the presence of a little starch mixed with the silicic acid. Some reduction of lead iodide must have taken place, possibly caused by the starch. 7. 7. Red mercuric iodide in 2 cm. needles or, in smaller crystals, banding in as many as forty regular bands in a distance of 8 cm. was obtained by the diffusion of a mercuric chloride solution into a silicic acid gel containing potassium iodide. With certain concentration conditions yellow crystals formed in front of the red needles and were finally changed into the red mercuric iodide. Soluble chlorides exerted a striking influence on the size, form, and arrangement of the mercuric chloride crystals. 8. 8. Magnificent red-black crystals of a basic mercuric chloride resulted when a saturated solution of mercuric chloride diffused into a silicic acid gel of slightly basic reaction. In a very slightly basic gel these crystals were grouped in a remarkable series of bands. The presence of a little glucose exerted a marked influence, changing the color and developing over one hundred compact bands in a distance of 8 cm. 9. 9. Silver sulphate crystals appeared in less than one hour when N silver nitrate diffused into a silicic acid gel made by mixing equal volumes of 1.06 density water-glass and 3 N sulphurie acid. In a few days orthorhombic slabs. 3 cm. long, developed If enough potassium dichromate to make the whole gel O.1 N molar with respect to this salt only was present, the long slabs were a beautiful clear red. In the presence of excess silver nitrate near the surface of the gel silver chromate was formed, and, since silver chromate and silver sulphate are isomorphous, red mixed crystals resulted. The color of the crystals was made any depth of red by varying the concentration of the potassium dichromate in the gel. Farther below the surface of the gel the silver nitrate became less concentrated, and triclinic crystals of the red-black silver dichromate appeared. In time they grew to a size 5 × 5 × 1 mm. 10. 10. Silver acetate grew in gleaming white sheets, 2 cm. long, when N silver nitrate diffused into a silicic acid gel made from water-glass and acetic acid. These crystals appeared in a few minutes. Such protective colloids as gum tragacanth, when present in very small amounts, twisted the straight crystals of silver acetate into fantastic shapes. 11. 11. Basic lead chromate was made in crystalline bands by diffusion of lead acetate solution into a silicic acid gel of alkaline reaction containing potassium chromate; urea nitrate in large crystals, by the diffusion of nitric acid into a silieic acid gel containing urea; perfect crystals, 5 mm. wide, of acid potassium tartrate and perfect crystals of copper tartrate in a silicic acid gel made with tartaric acid: and monosodium phosphate in large, colorless rhombohedrons by mixing disodium phosphate in a sodium silicate-acetic acid gel. 12. 12. Dry batteries discharging for short intervals developed colorless slabs, several centimetres in length, of ZnC 2 .2NH 3 next the zinc wall of the container. The gelatinous paste in this part of the cell caused slow diffusion of the zinc chloride, and ammonia formed by the discharge of the cell.

The colors of mother-of-pearl

Abstract: 1. 1. Mother-of-pearl owes its colors to two causes 1. (a) Diffraction of light due to a grating-like structure of the terminal edges of successive laminae. 2. (b) Interference of light due to reflection from numerous parallel laminae of sensibly equal thickness. 3. 2. By means of “replicas” the study 0f diffraction colors was carried out. Interference measurements were obtained in the infra-red region of the spectrum where conditions are much simplified. From these data the thickness of the laminae for many different samples was found to lie between the limits 0.4μ and 0.6μ.

The proteins of the peanut (Arachis Hypogæa)

Abstract: The ravages of the boll weevil have made it unprofitable to grow cotton in various sections throughout the South. In many regions where the growing of cotton has been decreased, peanuts are now being grown as a supplementary crop. This has caused a large increase in the production of peanuts in the United States. A number of mills which in the past produced cottonseed oil are now using their presses for the production of peanut oil. The press-cake thus obtained as a by-product is used for cattle food and sells at about thirty-five dollars a ton. This cake, therefore, furnishes a relatively cheap source of food with a very high protein content. The most striking result brought out during this investigation is the fact ‘that the globulins of the peanut contain a high percentage of basic nitrogen when compared with the proteins of other seeds commonly used for food. Work on the hydrolysis and separation of the amino-acids of the peanut globulins is in progress and will be reported in a later publication. The proteins of the peanut have received but little attention. The only published experiments seem to be those described by Ritthausenl in a paper which appeared in 1880. This author extracted oil-free peanut meal with a solution of sodium chloride and with solutions of potassium, calcium, and barium hydroxides. From the sodium chloride extract he obtained the globulin by saturating the diluted extract with carbon dioxide, or simply by diluting the extract with a large volume of water. Apparently the same globulin was obtained by acidifying the alkaline ex-

The reflecting power of tungsten and stellite

Abstract: acteristic, as will be shown in the present paper, is a marked depression at o.8/x in the reflectivity cm've. In a subsequent investigation ^ of the radiation from incandescent tungsten filaments the energy curves showed elevations in the smooth curve in the region of o.8/a to 0.9/x, which could not be attributed entirely to experimental errors. If tungsten has an indentation in its reflectivity curve, in the region of 0.8 to 0.9/x, similar to the indentations in the reflectivity curves of gold and of copper in the visible spectrum, then selective emission must ocour in this region of the spectrum similar to the selective emission of incandescent gold and copper in the visible spectrum. A further examination of the spectral reflectivity of tungsten was, therefore, made recently in order to verify these observations.

The characteristics of iron in high frequency magnetic fields

Abstract: Not many years ago it was quite generally believed that iron was unable to follow rapid magnetic changes. Experiments which showed an apparent decrease in the permeability of the iron with an increase in the frequency of the magnetic cycle furnished a basis for a theory that iron was magnetically sluggish. Further and more accurate experiments proved, however, that the effects which had previously been ascribed to a peculiarity of the material were in reality caused by eddy currents in the sample. Theoretical calculations were made which demostrated that eddy currents in an iron test piece increased as the square of the frequency and that for even the lower frequencies it was necessary to use quite thin laminations in magnetic circuits in order to eliminate deleterious effects. Furthermore, it was found that due to eddy currents and the magnetic properties of iron, the magnetization in high frequency fields was confined to a thin surface layer of the piece. This “Magnetic Skin Effect” reduced the cross section of the iron which was magnetically active even though the laminations were extremely thin. Careful experimental measurements compared with theoretical calculations proved that the real permeability of iron remained unchanged at frequencies up to about 106 and that previous results had been is serious error due to neglect of the factors mentioned. This fact having been established, efforts were made to see what practical use could be made of iron in high frequency work and to that end some extensive experimental investigations of the saturation curves and core losses were made upon specimens laminated as thinly as was commercially practicable. The resulting data have furnished a basis for design. It is a demostrated fact that the permeability of all metals is unity for the magnetic cycles imposed upon them by heat and light waves. In the region between frequencies of about 106, where the true permeability of iron is practically the same as at zero frequency, and frequencies of about 1010 where the true permeability of iron approaches unity, the experimental values of μ decrease smoothly with the frequency. What happens to μ in the range of frequencies between the lingest heat waves and the shortest Hertzian waves which have yet been made is a question which has many interesting features but which has not yet yielded to the experimenter.