Cent Nitric Acid Research Articles

The corrosion behavior of compositional modified AISI type 304L stainless steel for nitric acid application

Purpose High corrosion resistance in different concentrations of nitric acid is essential for structural steels to be used for the aqueous reprocessing of spent nuclear fuels with high plutonium content. Design/methodology/approach In the present study, the corrosion resistance of type 304L stainless steel (SS) with modified composition was evaluated in different concentrations of nitric acid using surface analytical techniques, weight loss method and electrochemical measurements. Findings Weight loss measurement in boiling 65 per cent nitric acid showed a low corrosion rate value of about 0.2 mm/y (8 mpy) after 240 h exposure. Electrochemical measurements revealed the shift in open circuit potentials as well as corrosion potential toward more noble direction, and the results of electrochemical impedance spectroscopy studies indicated the reduction in the thickness and stability of the passive film with increasing concentration from 6 to 11.5 M nitric acid. Research limitations/implications The low corrosion rate observed for this steel is attributed to the higher content of Cr (19 per cent), Ni (10 per cent) and Si (0.3 per cent) and controlled minor alloying elements (S, P, B, C, etc.) in the alloy that contributed to improving the transpassive corrosion resistance and minimizing the intergranular corrosion attack. The X-ray photoelectron spectroscopic analysis revealed the composition of the passive films to be mainly of iron and chromium oxides. Practical implications Materials with lower corrosion rates are desirable for applications in nitric acid. Social implications The used of nitric acid creates a severe corrosive environment in chemical or aqueous nuclear reprocessing plants, and hence with a modified composition of type 304L SS resulting in minimizing failure of components are desirable for reducing cost and maintenance. Originality/value The present paper is an original work carried out by the authors on the corrosion resistance behaviors of composition modified AISI type 304L SS for nitric acid application. The effects of different nitric acid concentrations were compared to provide understanding on in applicability in boiling and high nitric acid concentrations.

TEX: The New Insensitive High Explosive

Insensitive high explosive 4, 10-dinitro-2,6,8, 12-tetraoxa-4, 10-diazatetracyclo (5.5.0.0.5,9 03,11) dodecane (TEX) has been synthesised by an improved laboratory-scale process using 93 per cent to 96 per cent nitric acid as nitrating agent. Characterisation of the product was done based on its physical constants, infrared, differential thermal analysis, and mass spectral studies. Explosive and ballistic parameters of TEX containing formulations were computed using Becker-Kistiakowsky-Wilson (BKW) code and NASA Chemical Equilibrium Composition- 71 programme, respectively. Semi-empirical quantum mechanical calculations using the parametric model 3 (PM3) method have been carried out for the TEX molecule. The optimised geometrical parameters and heats of formation were obtained from semi-empirical PM3.

Multiple foci of atypical epithelial hyperplasia (tumourlets) in irradiated human lungs.

Small foci of atypical epithelial hyperplasia arising from respiratory bronchioles, alveolar ducts and alveolar epithelial cells have been named “tumourlets” by Whitwell (1955). They have been regarded as bronchial carcinoids or adenomas (Felton, Liebow and Lindskog, 1953; Prior 1953), early carcinomas (Petersen, Hunter and Sneeden, 1949; Stewart and Allison, 1943), and atypical hyperplasia, or metaplasia of bronchial and bronchiolar epithelium (Berkheiser, 1959; King 1954; Whitwell, 1955). Tumourlets have been described in lungs affected by bronchiectasis, chronic abscesses, fibrosis, nonspecific inflammation, anthracosis, and at the edge of old pulmonary infarcts (Evans, 1968). They have never been found in the absence of damage to the lung (Spencer, 1968). They have been produced experimentally in rabbits by the intratracheal instillation into the lungs of 1 per cent nitric acid, the animals being protected from the development of pneumonia by antibiotic cover (Totten and Moran, 1961). No reports describing the presence of tumourlets in irradiated lungs have been found in the literature. The finding of tumourlets in the lungs of a patient with multiple pulmonary metastases from malignant teratoma of the testis treated by radiotherapy, who has developed radiation pneumonitis, forms the basis of this report. The patient, a 37-year-old man, was admitted to hospital with possible torsion of his right testis at the beginning of November 1971. Two weeks previously he had noticed swelling of his right testis, which became increasingly painful.

Experimental bone tumours caused by common viruses.

ATYPICAL osseous and articular lesions have been observed in children in the course of measles and viral neuroinfections1,2. Although no viruses were isolated from the bones of the patients, the observations prompted the following investigation of the influence of viruses on bone tissue. In this communication we present the results of experiments with the ornithosis virus O.A.P. strain Y.S. 224, Coxsackie A9, Coxsackie B1, B3 and B4 viruses. The method used has been described before3. The experimental suspensions were free from bacterial contamination, as checked by inoculating various culture media. White mice of the ‘Porton’ race weighing 15 g each were used in the experiments. The suspensions were injected into bone marrow or joints. The Coxsackie A and B viruses were used in 25 per cent carcass suspensions, and the ornithosis virus in 15 per cent brain suspensions. The numbers of animals inoculated, the dosage of the suspensions and the frequency of lesions in the bones are shown in Table 1. Mice were anaesthetized in groups at intervals of 5 days, and inoculated parts were removed for histological examination. (The material was decalcified with 7 per cent nitric acid, fixed in paraffin, and stained with haematoxylin and eosin). In two mice, 25 and 35 days after inoculation, rapidly growing tumours were observed on the temporo-frontal aspect of the head in one case, and on the front limb in the other. The longest period of observation was 50 days.

Retention of Carbon Dioxide Bubbles on Calcite Etch-Peaks

THE etch-patterns on cleavage faces of calcite which have been reported1–3 bear some interesting similarities and dissimilarities to etch-patterns obtained in this Laboratory. Watts etched calcite for 30 sec. in 1 per cent nitric acid and obtained five-sided figures which he called pits. We immersed calcite in 0.001 N hydrochloric acid for one week and obtained essentially six-sided peaks (Fig. 1) with irregular valleys between them. The sixth side has a rougher surface than the other sides and it seldom extends to the apex of the peak. It may constitute an incompletely formed figure. Stanley used 10 per cent hydrochloric acid for 10–60 sec. and obtained figures which he describes as four-sided, although from his published photographs we detect a tendency of these figures toward the six-sided etch-patterns observed in our study. The Pandyas, using ammonium chloride, obtained parallelograms.

Metallographic Studies of Iron Carbide and Tungsten Carbide

IN most metallographic investigations of steels or of cemented carbides the fine details of the carbides are not studied. We have just completed an etching study of iron carbides made in three different ways and of some tungsten carbide (1/32-in. equilateral triangles) single crystals. The iron carbide studies, made with Carapella's reagent (5 gm. ferric chloride, 2 ml. concentrated hydrochloric acid and 99 ml. methyl alcohol) etching for 20–60 min., revealed cracking as the principal deformation mechanism and twinning as the secondary agency. The cracking behaviour has been described previously, but the twinning appears to be a new observation1. In two cases only, out of hundreds of samples studied, the cracks found were aligned along the twinning planes in the carbides. These observations were made upon a carburized plain carbon steel, upon a carburized ‘Westinghouse Puron’ iron (spectrographically pure) and upon a pure, massive, polycrystalline, iron-manganese carbide kindly supplied by Dr. L. S. Darken of U.S. Steel Research from his recent ternary system studies. In the two carburized samples there was no possibility of mechanical work having caused cracking of the carbide. Fused caustic, 50 per cent nitric acid and 50 per cent hydrochloric acid were also successful etching reagents.

A study of fast reactions in fuel-oxidant systems: Anhydrous hydrazine with 100 per cent nitric acid

A study of fast reactions in fuel-oxidant systems: Anhydrous hydrazine with 100 per cent nitric acid

Passivating Characteristics Of the Stainless Steels

While it has long been accepted that stainless steels , have the inherent ability to passivate in air or under other oxidizing conditions, investigation indicates that the rate of film growth and the degree of passivity attained vary considerably under different conditions. Solution potential measurements offer a convenient means of following the progress of the film formation. Data show the behavior of stainless steel specimens in various solutions and in air after a prior chemical activation. A 30 per cent nitric acid solution rapidly produces a passive potential as compared to air. A comparison of several stainless steel types in regard to their passivating characteristics is given and the effect of surface finish is also considered. Results suggest that in some instances stain-less steels probably owe their corrosion resistance to the formation of a protective film of corrosion product on the surface rather than to the passive film which, according to the usual concept, is caused by an oxidizing env...

Radiochemical Determination of Chromium, Vanadium and Molybdenum by means of Radioactive Silver

THE extreme sensitivity of measurements of radioisotopes makes it possible to use the artificial radioelements as an aid in analytical chemistry. In our experiments we have used radioactive silver for making quantitative estimations of small amounts of chromium, vanadium or molybdenum present in steel or in various substances. Insoluble silver salts can be prepared by means of these elements. Previous investigations have shown that all these silver compounds are suitable for radioactive measurements, except silver vanadate, which gives no reproducible results. Therefore, we dissolve the silver meta-vanadate in boiling 50 per cent nitric acid, and silver is precipitated as chloride; the latter is filtered on a fritted glass filter, so giving directly a radioactive sample for counting. A Geiger–Muller tube (R.C.L. Chicago) with thin mica window is used for the radioactivity measurements.

Comparison of Metallographic and X-Ray Measurements of Retained Austenite

THE martensite reaction in steels has been studied by microscopic examination of polished and etched samples after the samples have been tempered for short periods of time. One etching reagent which has been used is a solution of 6 per cent nitric acid in alcohol, which is called 6 per cent nital. This etchant stains the martensite grey or black and leaves the austenite white.

Estimation of Carbon Black in Neoprene Compounds

Abstract During a recent investigation it was necessary to determine the amount of carbon black in a sample of vulcanized Neoprene. The usual method adopted for vulcanized rubber, which consists in dissolving the rubber in nitric acid (British Standard Methods of Testing Vulcanized Rubber, B.S. 903–1940, p. 28), was tried without success, as the Neoprene did not dissolve. No methods for the analysis of Neoprene compounds appear to have been described in the literature; the following method of estimating carbon black, which has been found to work satisfactorily, may therefore prove of interest, especially as it can be used for certain other synthetic rubbers such as Buna. About 1.0 gram of the Neoprene sample is reduced to a fine crumb, such as will pass through a B.S. 10-mesh test sieve, by means of a rapidly rotating rasp. After extraction with acetone and chloroform, the extracted material is dried in a vacuum desiccator, transferred to a 400 cc. beaker, 20 cc. of nitrobenzene added, and the whole heated on a hot plate for a few minutes to allow the Neoprene to swell. 20 cc. of 25 per cent nitric acid (25 volumes of conc. nitric acid and 75 volumes of water) are then added, and the beaker is replaced on the hot plate. The Neoprene disintegrates and dissolves in the nitrobenzene in a few minutes. The beaker is then heated on a steam bath for about an hour, after which 100 cc. of xylene is added and the mixture filtered, while hot, through an alundum crucible or prepared Gooch crucible. The carbon is carefully washed with hot xylene till free from decomposed Neoprene, and finally with acetone. After drying at 150° C, the crucible is weighed, the carbon black then burnt off in a muffle furnace, and the crucible reweighed. The difference between these weights is the amount of carbon black present.

DECALCIFICATION OF TEMPORAL BONES: THE USE OF X-RAYS FOR DETERMINING WHEN DECALCIFICATION IS COMPLETE

In the decalcification of temporal bones, two important questions arise: 1. Which decalcifying fluid is best? 2. How can one know when the bone is actually decalcified? It is frequently stated that 5 per cent aqueous nitric acid is the most suitable decalcifying fluid. The temporal bones are placed in this solution, and fresh changes are made every few days until the bones are decalcified. Other acid solutions that have been used are hydrochloric acid and sulphurous acid. When hydrochloric acid is used, however, the outer parts of the bone seem to become so disintegrated that they are frequently lost. It has been my experience that even 5 per cent nitric acid solution in 70 per cent alcohol produces dissolution of the outer parts of the bone before the central part is decalcified. Thus, valuable tissue and landmarks are often destroyed. From 1 to 2 per cent nitric acid has

THE EFFECTS OF POLARIZATION UPON THE STEEL WIRE-NITRIC ACID MODEL OF NERVE ACTIVITY

The active process in a short length of steel wire passivated by 65 per cent nitric acid has been observed under the influence of a polarizing current, and the form of the potential recorded by the cathode ray oscillograph. In the passive wire, 80 per cent of the total potential drop takes place at the anode, 20 per cent at the cathode. The change from active to passive states, as measured by the potential change, is very abrupt compared to the duration of activity and the potential curve at a point on the wire is probably almost rectangular. The duration of the refractory state is decreased at the anode and increased at the cathode, as in nerve. This fact is against the idea that reactivity after passivation results from a partial reduction of an oxide layer. Soft iron wire passivated by anodal polarization repassivates after activation in acid of a dilution that fails to passivate it initially. It soon becomes rhythmic with a very short refractory phase, and then reacts continuously. Such a wire exhibits a very sharp alternation between a dark brown oxide coat during activity, and a bright clean surface during passivation. A passive steel wire in nitric acid shows many of the characteristics of an inert electrode such as platinum, and it may be inferred that, superposed upon the primary passivation potential, there exists an electrode or oxidation-reduction potential equilibrium between the effects of the various constituents of the solution. It is suggested that the phenomena of nerve-like reactivity in this system may involve an alternation between two protective coatings of the steel wire. During activity, the surface becomes mechanically coated with a brown oxide. If this coating does not adhere, due to gas convection or to rapid solution of the oxide, passivation does not result. Under sufficiently intense oxidizing conditions, a second oxide coat may form in the interstices of the first, and cover the surface as the first coating dissolves off. This furnishes the electrochemical protection of passivation, which is followed by the gradual attainment of electrode equilibrium with the solution.

Reduction Potentials of Organic Substances by the Lead Peroxide Electrode.

It has been pointed out frequently that the potentials measured in a solution of pure oxidant or pure reductant have a questionable meaning. Moreover such potentials are difficult to measure because they fall in a region of a curve approaching the potential axis asymptotically, and thus a slight change of conditions in the solution causes a wide fluctuation of potential. In such a solution an “inert” electrode, being unpoised, is subject to further fluctuation due to its own surface activity. The same considerations obviously apply to solutions of those reductants which tend to transform irreversibly into products not active at an electrode, such as most organic compounds. Various schemes have been proposed for the measurement of such potentials, which depend in general upon the addition of some other component which poises the system. It occurred to us that an oxidizing electrode might in itself have a poising action on an otherwise irreversible system. We have tried manganese dioxide and lead peroxide electrodes. In the following we report preliminary determinations with lead peroxide electrode on solutions of certain organic reductants. The electrodes were prepared by plating out lead peroxide on platinum electrodes, made anodal in a solution of lead nitrate acidified with eight per cent nitric acid, under voltage sufficient to cause evolution of a fine stream of gas bubbles. These electrodes read in buffer solutions far in the the oxygen overvoltage region. On long standing they approach the oxygen electrode potential, but still read sluggishly in a reducing solution. If placed in a solution of a reducer until equilibrated, then washed in buffer until they again approach the oxygen electrode potential, when next placed in a reducing solution, equilibrium is attained very promptly.

Heterakis vesicularis Frolich 1791: A vector of an infectious disease.

Several parasites, a flagellate of the genus Giardia and also microsporidia have been reported in intestinal round worms, but up to the present time the latter have not been shown to be concerned in the transmission of disease.Blackhead, an infectious disease of turkeys and other poultry, is caused by a flagellate, Histomonas meleagridis. It is transmitted experimentally and to some extent in nature by the direct ingestion of material contaminated with freshly passed discharges containing the protozoon. It appears, however, to be much more frequently transmitted indirectly by some phase distributed on the soil, evidently in association with the eggs of the caecal worm, H. vesicularis.The presence of the protozoon in the egg of Heterakis is indicated by experimental evidence of various sorts.1. Heterakis eggs kept in 1.5 per cent nitric acid until embryonated produce blackhead when fed to young birds isolated from all other sources of infection, although this treatment renders the material bacteriologicall...