Nitrate Bath Research Articles

Cathodic reduction of different metal salt solutions Part I: synthesis of metal hydroxides by electrogeneration of base

The yield of metal hydroxides obtained by electrolysis of chloride baths is greater than the yield obtained from nitrate baths showing that the hydrogen evolution reaction (HER) contributes as much to electrogeneration of base as the nitrate reduction reaction. This observation has implications for the fabrication of nickel hydroxide positive electrodes for alkaline secondary cells, and widens the scope of electrosynthesis to include chloride, sulphate and other anion containing α-nickel hydroxides and other layered hydroxides. Electrosynthesis of Mg(OH)2 has been investigated as a model synthesis.

DSC sample preparation for Al-based alloys

This work explores the conditions for safe heat treatment of aluminum alloys containing lithium and magnesium in molten sodium nitrate (NaNO3) bath furnaces, and conditions where industrial accidents may occur. Using calorimetry coupled to classical thermodynamics, the strength of classical thermodynamics when analyzing thermal curves was demonstrated through a series of small-scale thermal analyses of various aluminum alloys in contact with sodium nitrate. This system was selected to illustrate reactions that may lead to severe and violent heat effect phenomena. Using idealized binary alloys, severe oxidation of magnesium- and lithium-rich aluminum alloy samples were shown to occur near 500 °C, a temperature range dangerously close to the operating temperature of solution heat treatment furnaces in manufacturing processes of heat treatable aluminum alloy sheets used in the aerospace industry. Commercial aluminum alloys AW257, 2198, 2024, and 1050 were also assessed with the same tools. The temperature that needed to be reached for these commercial aluminum alloys to react with molten sodium nitrate was significantly higher than the normal operating temperature of a conventional solution heat treatment furnace.

Cyclic voltammetric studies of electrodeposited solid solution and composite oxide/hydroxide electrodes in 1 M KOH: the Co(OH) 2-Ni(OH) 2-MnO 2 system

Solid solutions of the type Ni 1- x Co x (OH) 2 ( x = 0.1 to 0.9) obtained by cathodic deposition from a mixed nitrate bath show a redox behaviour that is completely different to that of the pure components. The solid obtained from a bath containing a Ni/Co ratio of 40/60 exhibits the lowest E rev and the smallest difference between the anodic and cathodic peak potentials (0.03 V). This is indicative of the high reversibility achieved at this composition. A layer-by-layer deposited composite electrode Pt/Ni(OH) 2/MnO 2 shows the migration of the active nickel oxide species from the inner layer to the surface and a marked lowering in the E rev of the nickel hydroxide reaction. By contrast, the cobalt counterpart of this electrode does not show any of these interesting features. The Pt/MnO 2/Ni(OH) 2 electrode does not hold much promise as it exhibits a markedly reduced reversibility of the nickel hydroxide reaction. In the cobalt counterpart Pt/MnO 2/Co(OH) 2, MnO 2 profoundly affects the reactions of cobalt hydroxide: first anodic reaction is suppressed and the second anodic reaction is less reversible. These observations suggest that there is a common chemical reaction mechanism for all oxide electrodes in alkaline media.

Electrolytic recovery of tungsten and cobalt from tungsten carbide scrap

Tungsten and cobalt are recovered by an electrochemical method using nitric acid as the electrolyte. The method involves the oxidation of carbide material at the anode producing insoluble tungstic acid (H 2WO 4) and cobalt ions in the solution. Conditions for simultaneous oxidation of tungsten carbide and dissolution of cobalt have been investigated, using concentration of nitric acid, current density, temperature and time as the variables. The addition of cobalt, ammonium nitrate and potassium perchlorate has a beneficial effect on oxidation of tungsten carbide. Current efficiencies obtained for cobalt deposition from a nitrate bath are very low. Anodic behaviour of the cemented carbide is studied by polarisation curves and potentiostatic dissolution and the reactions occurring at the electrode are discussed.

Preparation and evaluation of selectively absorbing coloured stainless steel surfaces

Selectively absorbing surfaces have been prepared on bright annealed austenitic stainless steel type AISI 304 by two different chemical oxidation methods: immersion in aqueous acid (AA) and in molten sodium potassium nitrate (SPN) baths. Various immersion times and temperatures have been used and the solar absorptance α and thermal emittance ϵ were measured for each set of conditions. The oxide surface showed a decrease in total solar absorptance α t with increasing incidence angle of the beam. Thermal and chemical stability tests have also been carried out on the surfaces. The SPN surfaces exhibited the better high temperature stability as a consequence of the higher oxidation temperature.

Electrolytic production of silver powder using a vibratory cathode in cyanide electrolyte

Finely divided silver powder was prepared from a cyanide bath at a vibrating stainless steel cathode under potentiostatic control. The mechanism of the process was investigated using potentiokinetic methods, scanning electron microscopy and other techniques. The morphology of the powders obtained from cyanides was found to be quite different from that reported using the more conventional nitrate bath. Vibration was found to enhance considerably the mass transport to the cathode and thus enabled higher current densities to be used. This fact, rather than promotion of powder detachment, appears to be the main advantage of vibration.

Electrodeposition of silver on silver single crystals

The morphology of silver electrodeposits deposited on silver single crystals has been studied in sulphate, perchlorate and ammonium nitrate baths at several current densities. A. characteristic type of deposit was observed in the above baths. In presence of sulphadiazine and sulphadimidine, the growth habit changes depending upon the concentration and current density.

A new method for the reduced silver impregnation of arthropod central nervous systems.

A rapid reduced silver impregnation for arthropod central nervous systems is described. Material is fixed in Gregory’s Dubosq-Brasil or in Carnoy’s solution. Incubation of 2-3 μm sections in an urea-silver nitrate bath of the Ungewitter type is preceded by treatment with a dilute solution of mercuric chloride in 2% nitric acid in 70% ethanol in the presence of excess cobalt nitrate. Gold-toning follows conventional strategies. The method succeeds with a wide range of materials, and the results are comparable to those obtained with variants of the Bodian, Holmes and Bielschowsky routines.

Electrodeposition of silver from the system AgNO 3—ethyleneglycol—water. Effect of temperature ( ∼ −30°C) on the smoothness of silver deposits

The electrodeposition of silver from a nitrate bath can be improved by lowering the temperature and by the addition of ethyleneglycol as anti-freeze. When the bath temperature is lowered below 0°C, the dendritic silver deposition is suppressed and a smooth surface is obtained; at −30°C a very finegrained deposit results. The dendritic growth is supposedly prohibited partly by the lowering of temperature and to a less extent by the adsorption of ethyleneglycol at the surface both of which might enhance the activation overvoltage of silver deposition. From the polarisation measurement in, 0·25 M AgNO 3 electrolytes, the exchange current density of Ag deposition was evaluated as 1·70 × 10 −2 A/cm 2(25°C) and with 50 vol. per cent ethyleneglycol, 9·72 × 10 −4 A/cm 2 (25°C) and 1·22 × 10 −5 A/cm 2 (−32°C). Adsorption of ethyleneglycol on Ag cathode was discussed by differential capacitance change.

Growth spiral patterns in electrodeposited silver

To study the mechanism of crystal growth, silver electrodeposition on silver single crystal (100) surface was investigated by means of a differential interference microscope. The deposition was performed from an acid silver nitrate bath containing a small amount of the additives at various current densities. It was found that poly-amideamine played an important role in the conditions under which spirals grew. The screw dislocation groups of large Burgers vectors are produced by adding additives to the electrolytes, which indicates the importance of the impurities in the formation of screw dislocation groups. A mechanism for the formation of macro-steps by drawing together monatomic steps is discussed in terms of “step-bunching”. Several patterns of spiral growth, which were very useful to know the mechanism of basic crystal growth, were observed in electrodeposited silver. The growth patterns for two or more spirals on the deposit are also reported in relation to the theory of crystal growth.

Effect of addition of lead acetate during the deposition of lead dioxide from the nitrate bath

When lead dioxide is deposited from lead nitrate solution the free nitric acid produced during the electrolysis affects the optimum pH of the bath, and thus the physical characteristics of the deposit. Although this is effectively prevented by neutralizing the free acid either with lead carbonate, or lead monoxide and copper carbonate, the pH of the anode film is still more acidic than the bulk of the solution. To maintain pH almost constant lead acetate can be used as a buffer. We have studied the effects of lead acetate, and have examined the throwing power of the bath. Stress measurements during the deposition of lead dioxide, anode potential measurements and X-ray studies of the deposit have also been carried out.

Chemical Structure and Properties of Heat Treated Coal in the Early State of Carbonization (III)

Much sample of uniformly heat-treated coal was prepared by using a nitrate bath in which the vessel containing a thin layer of coal sample was heated. The Japanese Nishikawachi strongly coking coal was added to the sixteen vitrain samples described in previous paper. These samples were heat treated with a heating rate of 3°C/ min. over the range from heat treatment temperature (HTT) 200°C to 500°C at intervals of 50°C.The yield of products the state of devolatilization have a strong correlation with the chemical constitution of original coals. Therefore, the yield of products at HTT 500°C is analogized from the proximate and ultimate analytical constitution of original coals.The analytical constitution of heat-treated coals depends on HTT and coal rank.In general, the beginning temperature of change in heat treatment increases with the increase of coal rank. The chemical constitution of heat-treated coals hardly changes below HTT about 350°C, except the lower rank coals below about 80% C. It seems, however, that the change of physical structure of heat-treated coals may happen below HTT about 350°C.At HTT about 400°C, the chemical constitution in coking coals of 83-87%C begins to change and the devolatilization rate of the lower rank coals shows a maximum. For coking coals, the devolatilization becomes violent and the ultimate analytical constitution of heat-treated coals changes largely at HTT about 450°C. At HTT about 500°C, the change of chemical constitution in strongly coking coals of about 90% C becomes remarkable.The reaction occured by heating up to HTT 500°C is mainly dehydration for lower rank coals. Dehydration and then demethanation predominate with the increase of coal rank.The aromaticity of heat-treated coals increases suddeny with the increase of HTT. The aromaticity and the chemical constitution of heat-treated coals at HTT 500°C do not show so large difference each other in comparison with the large difierence in original coals.

Lead Dioxide Anode for Commercial Use

Results are presented on one phase of a research carried out under an Office of Naval Research contract for the development of an electrode to replace platinum in the perchlorate cell. Electrodeposition of massive lead dioxide is preferably carried out from a lead nitrate bath. Uniquely, anodic deposition on tantalum is possible without polarization or erosion of the base. In the subsequent anodic process use, this tantalum acts as a polarized, inert filler. Sprayed silver permits the formation of an operable, low resistance current contact to the lead dioxide. Operation of a 100 amp perchlorate cell with a lead dioxide anode is described. Current efficiency of the lead dioxide anode is compared to platinum, and the effect of addition is shown.

Differentiation of Myofibrillae, Reticular and Collagenous Fibrils in Vertebrates

A procedure for the differentiation of the mesenchymal derivatives, myofibrillae, reticular and collagenous fibers is presented. Formol-Zenker fixation (5-12 hours) is followed by the washing, iodinization, dehydration and paraffin embedding steps routine for that fixative with the following modifications. Zirkle's butyl alcohol series is used for dehydration and infiltration with paraffin as well as in the alcohol slide series. Embedding paraffin used is Parawax plus 8-10% bayberry wax. Tissue-exposed surface of paraffin block is soaked in water overnight before cutting serial sections at 3-5μ. Sections are mounted using the dilute albumen method, and the slides, thoroughly dried at 37oC. overnight, are left at 60o for 10 minutes to melt the paraffin of the sections. Before staining, the sections are given a preliminary treatment with potassium permanganate and oxalic acid. For reticular staining a 10% silver nitrate bath is succeeded by an ammoniacal silver carbonate solution followed by reduction in 1% neutral formalin, toning in gold chloride and fixing in sodium thiosulphate. Myofibrillae, the sacroplasmic limiting membrane and other sarcous elements are stained by Heidenhain's azocarmine solution, adult tissues at room temperature and fetal tissues at 50 oC. Differentiation in phosphotungstic acid is followed by the staining of collagenous fibers. For adult tissue, light green SF (C.C.) is used and for fetal tissue, fast green FCF (C.C). A discussion of the preparation of ammoniacal silver solutions is included. Both stock and used solutions of ammoniacal silver have been in use by the author for over a period of two years.

The Bearing Strength of Steel and Aluminum Alloy Sheet in Riveted or Bolted Joints

T object of this investigation was to develop ''tear-out design criteria by means of which the strength of the material outside the bolt or rivet in a joint in tension could be more accurately determined. As test data were obtained and studied it became apparent that the edge distance had a definite relationship with the bearing strength and the test program accordingly was arranged to show how the bearing strength varies with the edge distance, with bolt or rivet size and with sheet thickness. A number of typical test specimens are shown in Fig. 1. In all cases the specimen was made of two pieces of 24ST aluminum alloy or chrome-molybdenum steel sheet fastened together with a single bolt or rivet. The bolts were of steel heat-treated to an ultimate tensile strength of 125,000 lbs. per sq.in. and were used in all cases in double shear. The rivets were made from 17S aluminum-alloy rivet wire purchased under Army-Navy specifications and heat treated in a nitrate bath to an ultimate tensile strength of 55,000 lbs. per sq.in. They were used in all specimens in single shear. All specimens were tested in tension to failure. Most of the specimens were formed with square ends. A few, however, were made with rounded ends. Of the latter specimens some had the bolt hole drilled concentric with the rounded end, some had the hole drilled with a plus offset and some with a minus offset, noted in the presentation of the test results. To clarify the offset designations it may be stated that when the distance from the center of the hole to the end of the lug was less than the radius of curvature of the rounded end, the offset was assumed to be minus. The sheet stock used in these tests was purchased under Army-Navy specifications. Test coupons were cut from the 24ST material and showed an ultimate tensile strength that varied from 68,100 to 73,700 and averaged 71,000 lbs. per sq.in. The bearing values obtained in the tests were not corrected to a common ultimate strength. In the case of the chrome-molybdenum steel specimens tested in the as received condition, the test coupons showed a variation in ultimate strength of 71,800 to 83,500 lbs. per sq.in. The

STAINING NERVE FIBERS IN MOUNTED SECTIONS WITH ALCOHOLIC SILVER NITRATE SOLUTION

The procedures to be described have developed through experiments designed to test the effects of varying some of the many conditions involved in silver staining. The previous article 1 on staining nerve fibers in unmounted celloidin sections gave the technic from which the present method has evolved. The application of silver solutions to mounted sections with subsequent reduction of adsorbed or chemically combined silver salt is not new. Sand 2 embedded nerve tissue in paraffin after fixation in a strong solution of nitric acid in acetone and later impregnated the mounted sections. Malone 3 described a method for handling paraffin sections to produce a Cajal type of stain. Brandt and Kadanoff 4 investigated the effect of varying the time of impregnation and the concentration of the silver nitrate bath on sections from celloidin, paraffin and gelatin embedded material. They chose gelatin as best suited to the O. Schultze method. More