Small Amounts Of Sulfur Research Articles

The kinetics of dissolution of chalcopyrite in ferric ion media

The kinetics of dissolution of chalcopyrite (CuFeS2) in ferric chloride-hydrochloric acid and in ferric sulfate-sulfuric acid solutions have been investigated using the rotating disk technique. Over the temperature range 50 to 100‡C, linear kinetics were observed in the chloride media while nonlinear kinetics were noted in the sulfate system. The apparent activation energy in the chloride system was about 11 kcal/mole. The rate increased with increasing ferric chloride concentrations but was insensitive to the concentrations of hydrochloric acid, the ferrous chloride reaction product and “inert≓ magnesium or lithium chlorides. Cupric chloride substantially accelerated the rate. Small amounts of sulfate in an otherwise all chloride system greatly reduce the chalcopyrite leaching rate; still larger amounts of sulfate make the system behave essentially like the slower-reacting ferric sulfate medium.

The influence of dose on the pattern of conjugation of phenol and 1-naphthol in non-human primates.

1. The pattern of conjugation of phenol and 1-naphthol was investigated in several primates; three Old World species (rhesus, cynomolgus, patas monkeys), two New World species (capuchin, tamarin), and two prosimians (bushbaby, tree shrew). 2. Following intra-muscular phenol or 1-naphthol (10 mg/kg), sulphation was the major conjugation in the Old World monkeys and prosimians, whereas glucuronidation predominated in the New World species. 3. In rhesus and cynomolgus monkeys, sulphation decreased as dose increased, but remained the major conjugation with both substrates at dose levels of 0.01 to 25 mg/kg. 4. In the capuchin, the conjugation pattern of phenol changed markedly as dose increased; at 0.01 and 1 mg/kg sulphation was the major conjugation, whereas at 10 and 25 mg/kg glucuronidation predominated. With 1-naphthol only small amounts of sulphate were excreted; glucuronic acid conjugation was the major metabolism at all four dose levels. 5. The importance of considering both substrate and dose when making inter-species comparisons, particularly with man, is discussed.

Indirect determination of fluoride by EDTA back-titration of lanthanum

Semimicro to macro amounts of fluoride ion (0.4–100 mg) are determined rapidly and accurately by precipitation with an excess of lanthanum at pH 2.5–2.8 by digestion on a water-bath, cooling to room temperature, addition of excess of EDTA and back-titration of the excess with zinc solution to the Xylenol Orange end-point at ph 5.8–5..9. Large amounts of chloride, acetate and perchlorate, and small amounts of sulphate and silicate do not interfere, but phosphate does. This method is much superior to the usual thorium nitrate titration method and can be applied after preliminary separation of fluorine by steam distillation or pyrolysis.

A Study of the Effectiveness of the Standard Surface Cleaning Techniques as Applied to Ni(111), Ni(100), and Ni Sheet Using Auger Electron Spectroscopy (AES)

An investigation of the standard surface cleaning techniques, e.g., oxygen reaction at high temperatures and argon ion bombardment, has been carded out with special reference to Ni(111), Ni(100), and Ni sheet using Auger electron spectroscopy (AES) to monitor surface conditions. Carbon, sulphur, chlorine, nitrogen, and oxygen are observed as impurities on these surfaces. On Ni(111) a heavy carbon deposit (> 10 A thick) is noted. Argon ion bombardment is not effective in removing this layer. High temperature reaction (> 700°C) with oxygen is required to eliminate the surface carbon. The kinetics of this reaction are recorded by monitoring the rate of production of carbon monoxide dNCO/dt which obeys the relationship dNCO/dt=kPO20.9±0.1 exp−(32±2 kcal mol−1)/RT in the temperature range 663–917°C and oxygen pressure range 1.0×10−8 to 5.9×10−7 Torr. After this carbon removal the sulphur and chlorine impurities are eliminated using argon ion bombardment. Reaction with oxygen at 1100°C and 10−6 Torr is also effective in removing these latter impurities. At this point only a small carbon peak due to slow diffusion from the bulk is present on the surface. However, a short anneal to 700 °C for <1 min caused small amounts of sulphur and chlorine to reappear. This effect is discussed in terms of diffusion and support effects. The minimum attainable coverage (θs) of sulphur on the Ni(111) was θs=0.1. For Ni(100) and Ni sheet a much smaller carbon peak compared to Ni(111) is observed. This may be “removed” by heating alone. Some reaction of surface carbon and oxygen takes place to give gaseous carbon monoxide. Some carbon diffuses into the bulk. On cooling, carbon slowly diffuses to the surface. Sulphur and chlorine impurities may be removed by argon ion bombardment. Removal of these impurities by oxygen reaction at high temperatures is unsatisfactory. Oxidation occurs. Hydrogen reduction is not particularly successful, although this oxygen can be removed by prolonged argon ion bombardment.

Vapour phase chemistry of arenes. I: Thermolysis of benzene and derivatives; the effect of additives. Evidence for free radical chain processes

AbstractThe rate of the conversion of benzene into biphenyl (“tank flow” reactor, atmospheric pressure, nitrogen dilution, 540°) is found to be highly dependent on type and concentration of additives. For example, small amounts of sulfur or oxygen lead to strong retardation, but a little formaldehyde or C2Cl6 has a profound accelerating effect. Wall (memory) effects are also observed.These facts point to a radical chain mechanism ‐ involving H· and phenyl radicals ‐ rather than to a (bi)molecular process as was recently proposed by Fields and Meyerson. Other phenomena (H/D exchange, oxidation to phenol) are also consonant with a (semi)quantitative description based on thermo‐chemical kinetics.The thermolysis of other arenes can be explained analogously; thus, biphenyl (giving benzene, ter‐ and quater‐phenyls) forms H·, C6H5‐C6H4· and phenyl radicals as intermediates, the latter fragments arising through H· + biphenyl → (C6H6‐C6H·5.→ benzene + phenyl.

Indirect Complexometric Estimation of Boron and Its Application in Glass, Enamel and other Ceramic Materials

A simple method for indirect complexometric estimation of boron has been worked out in which boron is precipitated as barium-boro-tartrate at pH 10.0 with excess barium and tartrateions and the excess barium is directly titrated at a temperature below 20°C with EDTA using a sensitive mixed indicator comprising Eriochrome Black T, Titan yellow and Naphtholgreen B. Small amounts of sulphate (5 mg), phosphate (5 mg), chromate (6 mg), silica (3 mg), aluminate (5 mg) and fluorine (10 mg) do not interfere but presence of higher amounts of these ions cause positive error due to precipitation of respective barium salts. The interference can, however, be avoided by precipitating them out with barium chloride prior to the precipitation of boron. The method has been successfully applied for the estimation of boron in glass and other complex silicate materials and the results agree well with the standard values.

AMORPHOUS SILICA DEPOSIT AT ONI-KOBE DISTRICT, MIYAGI PREFECTURE, JAPAN

The amorphous silica deposit formed as masses near the surface at the southern foot of Mt. Arawo-dake occurs in the mudstone of Uppermost Miocene-Pliocene age. Various minerals such as kaolinite, opal, and alunite which are characterized by acid alteration occur around and within the silica deposit. A small amount of sulphur is sublimated in the fissures and cracks in the silica ores. The silica ores contain 80 to 96 percent of SiO2 (in dry matter), and are almost soluble by two normal NaOH solution at 100°C. This deposit is considered to have been formed by the action of strong acid fluid containing a large amount of sulphuric acid and to be related with recent volcanism. The characteristic features of the amorphous silica ore from Oni-kobe are discussed, and it is concluded that amorphous silics is composed essentially of “xerogel”.

3.5%ニッケル鋼溶接金属の熱間割れに対するジルコニウム,チタンおよびマンガン添加の効果

It is well known that a low melting point filmy sulfide causes hot cracking in a steel weld metal. Especially, in the case of nickel steel weld metal containing over 2.5% of nickel, the occurrence of such hot cracking becomes more significant even in a small amount of sulphur, such as 0.01 %. In this paper, the effect of alloying elements, which can effectively change the iron sulfide film into other sulfides of higher melting point and of globular form, was studied to prevent such not cracking.The experimental result showed that hot cracking of 3.5% Ni steel weld metal can be prevented by addition of strong sulfide forming elements, like zirconium or titanium. These elements are much more effective to prevent such hot cracking than manganese. Sulfide inclusion of these elements seems to be globular type of MnS, TiS or ZrS, respectively.

Slowly available sulphur fertilizers in South-western Australia. 1. Elemental sulphur

At Pinjarra and Bakers Hill, Western Australia, the rate of breakdown of elemental sulphur applied in different size gradings was followed over two seasons by periodically measuring the elemental sulphur remaining in the soil. Similar measurements were made on experiments at Kwolyin, Darkan, and Pinjarra in which commercial sulphur fertilizer was applied in the autumn of two successive years. Particles finer than about 200 mesh oxidized quickly and would be a poor source of slowly available sulphur. Particles between 40 and 100 mesh appeared to provide the best compromise between too fast and too slow oxidation. Oxidation appeared to be faster at sites with higher annual rainfall and faster in the second year of application than the first. The commercial sulphur fertilizer was an effective source of slowly available sulphur and produced pasture responses at all three sites in the first year. Responses continued into the second year but the level of effectiveness relative to a current dressing could, not be accurately measured. At the Pinjarra site, two annual applications produced a 2.5-fold increase in yield of clover. A total of 19 soils were tested in incubation experiments for their ability to oxidize sulphur. All soils were able to do this and differences between soils were small when small amounts of sulphur were used. Differences between soils were larger when large amounts of sulphur were used.

Rapid determination of small amounts of sulphate in cellulose nitrate by a water-digestion procedure

Oxidative decomposition of cellulose nitrate into a completely water-soluble material is accomplished by an aqueous digestion method that involves boiling it with water under pressure. Sulphate is quantitatively liberated, and most of the nitrate groups are decomposed, thus minimising errors from co-precipitation of the nitrate ions. The digests, which are completely free from inorganic additions, allow rapid sulphate determination by direct titrimetric procedures.

Skeletal muscle ribosomal proteins: General characteristics and effect of diabetes

1. 1. Skeletal muscle and liver ribosomes contained a similar, if not identical, heterogeneous group of basic proteins. The proteins had approx. 18 moles percent of acidic, and about 27 moles percent of basic residues; there were only small amounts of sulfur containing amino acids and of tryptophan. Alanine, glycine and serine accounted for most of the N-terminal amino acids, although there were also lesser amounts of valine, proline, methionine, aspartic acid and glutamic acid. 2. 2. The proteins of skeletal muscle ribosomes had great electrophoretic heterogeneity (there were at least 25 bands); the pattern of bands was, however, the same as with proteins from liver ribosomes. 3. 3. Each ribosome subunit from skeletal muscle contained a number of unique proteins; some of the subunit proteins had the same electrophoretic mobility. The pattern of the proteins from whole ribosomes was reconstituted when the 60-S and 40-S subunit proteins were combined and coelectrophoresed. From analysis of the subunits it appears that the minimum number of ribosomal proteins was 33. 4. 4. Diabetes did not produce a detectable alteration in the electrophoretic pattern of skeletal muscle ribosomal proteins.

The mineralization and hardness of the radular teeth of the limpet Patella vulgata L.

A study of the Patella vulgata radula has been made using: the scanning electron microscope in its normal and compositional contrast modes of operation, the electron microprobe analyser, ion etching with argon ions and microhardness testing. Only iron, silicon and small amounts of sulphur were detected in the radula. The teeth can be subdivided into a cusp, a junctional area where the cusp is joined to the base, and the base which is embedded in the radular membrane. From a study of longitudinal vertical and transverse sections of the mature teeth it was found that the cusp could be subdivided into a posterior iron-rich area (44–51% Fe, 1–6% Si) and an anterior silicon-rich area (22–30% Fe, 27–32% Si). The junctional zone consisted of a poorly mineralised layer at its border with the cusp and an iron-rich layer where it joined the base. The upper part of the base (5% Fe, 16% Si) could be clearly differentiated from the silicon-rich anterior and lower parts of the base (3–4% Fe, 28–35% Si). No minerals were detected in the membrane. The changes in the mineral content of the teeth cusps along the length of the radula were studied. Iron appeared in the cusps at the 25th row and the concentration increased to 28% at the 50th row. The iron was here evenly distributed throughout the cusp. Silicon appeared in the anterior part of the cusp at the 50th row and as it increased in concentration so the iron was displaced, and at the same time the concentration of iron increased in the posterior part of the cusp. Mineralization appeared to be complete by the 150th row. The teeth cusps appear to consist of 800 A fibres grouped into 1μ thick bundles and the tooth appears to be covered by a thin enamel-like layer. It is suggested that the fibres contain the silicon-rich phase and the matrix the iron-rich phase. The significance of the arrangement of the fibres and the distribution of the minerals are discussed with relation to the function of the teeth.

On the Manufacturing of Porous Bronze Powder by Atomization

In order to improve the poor compactibility of atomized bronze powder, the authors re-ex-amined the producing process. First powders containing small amounts of sulfur were produced, then, these powders were subjected to oxidation and finally reduced. The powder obtained showed outstanding compactibility in comparison with that of those powders obtained by mixing each component powder. .The results were summarized as follows:1. The optimum oxidizing temperature was 800°C.2. The retained sulfur in the powder decreased with increasing oxidizing time.3. The optimum reducing temperature after oxidation was 550°C and the reduced cake was crashed easily.4. Apparent density decreased with increasing sulfur content and oxidizing time.5. Weight decrease by Rattler test was found in the low percent range and the powder was found excellent in comparison with conventional atomized bronze powders.

Diminishing the role of sulfur oxides in air pollution.

Each year, in the US, more than 20 million tons of sulfur are discharged into the atmosphere, most of it in the form of SO/sub 2/. This gas is slowly converted into sulfuric acid, which is corrosive to many materials, including metals, building stones, and clothing. The toxicity of SO/sub 2/ and H/sub 2/SO/sub 4/ to plants and animals is controversial, as is the effect of these compounds when they are inhaled along with other components of smog. Principal targets for such restrictions are electric power generating plants. These are a major source of air pollutants when they use coal or residual oil as fuel. Five means of meeting the sulfur pollution problem seem feasible. One is to use fuel containing only small amounts of sulfur. A second is to discharge the fumes from tall smokestacks (more than 200 meters high). A third method is to add a material such as powdered limestone to the flue-gas stream, following combustion, to convert the gaseous sulfur oxides into a solid form. A fourth is to convert the coal to gas and to remove the sulfur from the gas prior to combustion. A fifth method is to pass the flue gases through amore » chemical processing plant, the sulfur being recovered in elemental form or as H/sub 2/SO/sub 4/. Both the sulfur and the H/sub 2/SO/sub 4/ are consumed on a large scale. The price of sulfur has advanced sharply during the last year and is currently quoted at close to $50 a ton. With present technology the value of the sulfur recovered from coal-fired power plants would about offset the cost of investment and operation of the processing plants. A combination of better technology with a higher price for sulfur may eventually convert a nuisance into a valued asset.« less

Estimation of Small Amounts of Sulphate by Precipitation with Radioactive Barium

IN the course of work on the metabolism of sulphur amino-acids in malnourished infants it was necessary to measure total sulphate concentration in large numbers of urine samples. The urine from these patients is very dilute, so that to obtain accurate results by the classical gravimetric or titrimetric methods it would be necessary to use large volumes. This is inconvenient, since for the oxidation of organic sulphur the urines have to be digested with concentrated acid. By precipitating with barium chloride containing radioactive barium, and measuring the radioactivity in the precipitate, the estimation could be made on 0.1–0.5 ml. urine.

The distribution of sulphur in the muds, water and vegetation of Lake Victoria

The sulphur contents of the muds, water and vegetation at the northern end of Lake Victoria have been determined. Contrary to previous assumptions it was found that the sulphur in the bottom deposits is principally in the form of organic compounds and not as sulphides. Evidence is presented which suggests that the muds are in an aerated condition. The water of the lake contains extremely small amounts of sulphur and receives a negligible quantity of this element from the rain. The soils of the islands in the lake are rocky and well-leached of sulphur except where patches of forest conserve it. Certain peculiarities were noted in the behaviour of the muds and these are to be discussed in a future paper.

Radiation Effects on Aqueous Thiourea Solutions

Thiourea and elemental sulfur (1), as well as other compounds containing sulfur in labile organic and inorganic linkage, play an important part in radiation chemical reactions in vitro and in vivo (2-5), owing to their protective action against radiation effects. The protective power of a substance in aqueous solution means its ability to decrease or abolish the effect of radiation on another solute, and this depends on the relative probabilities with which the two substances eliminate radicals formed from the solvent (water) by radiation. Very low concentrations of solute decrease the probability of collision between solute and radicals and therefore favor the recombination of radicals. At higher concentrations of solute this competing recombination gradually becomes negligible; i.e., the radiation yield increases. For some substances a constant yield is reached; for others the yield continuously increases with concentration. This variation in concentration dependence is not yet fully understood, as pointed out in previous communications (6-9). A possible explanation is that with good protectors, i.e., good acceptors of radicals, the recombination of radicals will become more negligible at lower concentrations than with inefficient ones, leading to a constant number of molecules changed per 100 ev (G). Other factors, e.g., molecular weight and shape of molecules, in particular in proteins, may be additional causes. It was observed in preliminary experiments that the amounts of sulfur liberated by ionizing radiations from thiourea increased with concentration without reaching a constant value, although this substance is a good protector. Because of this apparent contradiction in the yield/concentration relationship, it seemed of interest to investigate the radiation chemistry of thiourea in greater detail. The results obtained exceeded the initial purpose of the investigation and revealed various interesting and unusual features in the radiation reaction. Since the preliminary experiments were carried out with the crude technique of weighing very small amounts of sulfur, a more quantitative procedure was adopted 35

Determination of Total Sulfur in Rubber

Abstract With the recent increase in research on natural and synthetic rubber, there has arisen a need for a rapid method for the determination of total sulfur in rubber samples where only a semimicrosample can be spared for analysis. The usual methods in which the rubber is oxidized by digestion with acid, followed in some cases by fusion to complete oxidation, and the sulfur is precipitated and weighed as barium sulfate, yield good results on semimicro-samples, but are time-consuming, because quantitative precipitation of the sulfate cannot be attained unless the solution is allowed to stand overnight before filtration. Several volumetric methods, most of which depend on the precipitation of sulfur as barium sulfate, have been described, but none is very satisfactory in the determination of small amounts of sulfur. St. Lorant has proposed a volumetric method for the determination of microsamples of sulfate, in which the sulfate is reduced to sulfide with hydriodic acid, and the hydrogen sulfide is distilled off and determined colorimetrically. The author has recently developed a modification of this method which has proved to be very satisfactory for the analysis of sulfur in small samples of rubber. The procedure consists essentially of oxidation of the rubber in the usual manner, reduction of the sulfate to sulfide, separation of the hydrogen sulfide by distillation, and titration of the latter iodometrically. The new method is very rapid (20 to 25 minutes for the distillation and titration), and is not subject to the errors of adsorption, occlusion, and solubility encountered in the gravimetric barium sulfate method, or to difficulties in detection of the end-point encountered in some volumetric methods. It possesses the distinct advantage over some of the gravimetric methods that it is applicable to the analysis of rubber containing barium, lead, and calcium. The only serious objections to the method from the standpoint of general use are that hydriodic acid is expensive and that the applicability of the method is somewhat limited because of the fact that no more than about 5 mg. of sulfur can be handled conveniently. This means that the sample size must be small when analyzing rubber high in sulfur; and when small samples are used there is always the danger of error due to unequal distribution of sulfur in the sample.

LIVER DAMAGE AND URINARY EXCRETION OF SULFATE IN RATS FED l-CYSTINE, dl-METHIONINE, AND CYSTEIC ACID

1. Rats fed l-cystine at excessive levels excrete large amounts of sulfate sulfur in the urine and develop liver necrosis and cirrhosis. 2. Rats fed dl-methionine at excessive levels excrete large amounts of sulfate sulfur, but do not develop liver necrosis and cirrhosis. 3. Rats fed cysteic acid at high levels excrete relatively small amounts of sulfate, but do develop liver necrosis and cirrhosis. 4. In conclusion, there is no apparent correlation between the amount of sulfate formed and the development of liver damage in rats fed l-cystine, dl-methionine, and cysteic acids.

A Theory of Protein Metabolism in Man

During a 24-hour period when the subject is maintained in nitrogen balance with either protein, or a mixture of amino acids, or a single amino acid, the larger fraction (60-75%) of the nitrogen metabolized in this period is derived not from the nitrogen ingested during this interval, but from that already present. In this sense the bulk of the protein metabolized in any one day is endogenous. The term endogenous is used here in a different sense from the connotation given it by Folin, who used it to designate the wear and tear quota of protein metabolized. The simplest direct evidence for the above conclusion was furnished by experiments in which a mixture of amino acids and protein was ingested containing only a small amount of sulphur. These experiments showed that under these conditions there is no sparing of the basal sulphur. In several instances more sulphur was excreted than the sum of the amount ingested and the total excreted during a fasting period of 24 hours. It follows therefore that when protein is ingested the nitrogen and sulphur excreted do not come for the most part from the ingested protein; but that approximately three quarters is derived from protein (or protein split products) already in the organism.