Spectrophotometric and gravimetric determination of sulfur in sebacate-base lubricants

Sulfur is determined in sebacate-base lubricants spectrophotometrically and gravimetrically. In the spectrophotometric method, a 0.2–0.3-g sample is treated with mixed acids, magnesium chloride is added, and the solution is evaporated to dryness. The sulfate is reduced to hydrogen sulfide by treatment with a mixture of hydriodic. hypophosphorous, and hydrochloric acids, and the hydrogen sulfide is distilled into ammonia solution. Lead citrate reagent is added and the brownish yellow color of lead sulfide sol is measured. An improved technique and apparatus for the distillation is described. In the gravimetric method, a 5-g sample is treated with mixed acids, antimony and tin are volatilized by treatment with hydrobromic acid, and sulfur is precipitated as barium sulfate. The recommended range of the spectrophotometric method is 0.005–0.15%,and that of the gravimetric method is 0.01–1% sulfur.     

Radiometric determination of sulfate

A radiometric procedure for the determination of sulfate based upon the precipitation of barium sulfate is described with a sensitivity of about 0.01 μg/ml. Carrier-free³⁵SO₄ is added to the sample to measure the chemical recovery. The sulfate is precipitated with an excess of barium having a known specific activity of¹³³Ba. The amount of¹³³Ba determined by gamma counting is directly related by stoichiometry to the amount of sulfate in the precipitate.     

The determination of microgram amounts of sulphur in nitrate or chloride solutions

It is shown that μg quantities of sulphate can be “collected” with barium chromate when the latter is precipitated from solutions at a pH of about 1. The sulphate in this precipitate can be converted to hydrogen sulphide when the precipitate is treated at red heat with a mixture of hydrogen and hydrogen chloride vapour. The above procedure has been made the basis of a method for determining traces of sulphur, down to about 0.2 p.p.m. on a 10 g sample, when the hydrogen sulphide is determined absorptiometrically as Lauth's violet.     

The determination of microgram quantities of fluoride: The use of the aluminium-chromeazurol-s complex

A spectrophotometric method for determining fluoride using the aluminium chromeazurol complex is described. Fluoride in solution free from interfering ions or obtained by distillation as hydrofluosilicic acid is determined by destruction of the complex, the amount destroyed being directly proportional to the fluoride present. The method will detect as little as 0.02 μg/ml of fluoride and with 0–20 μg in the final solution fluoride can be determined with an accuracy of ± 0.6 μg.     

The determination of zirconium in fluoride-containing solutions

In the recommended procedure the zirconium is first precipitated from solution as the insoluble barium fluozirconate. After separation, the precipitate is dissolved in a mixture of nitric and boric acids and the zirconium is then precipitated as its hydroxide. This precipitate is separated, dissolved in hydrochloric acid and this solution is evaporated to fumes of perchloric acid to remove completely fluoride ions. The zirconium content is then determined volumetrically by adding a slight excess of a standard solution of ethylenediaminetetra-acetic acid and back titrating with a standard iron solution at pH 2.3 using potassium benzohydroxamate as indicator and the photometric technique for end-point detection. This method is applicable to the determination of milligram amounts of zirconium in fluoride-containing nitric or hydrochloric acid solutions provided that the concentration of these acids is below 3N. It is also suitable for the determination of zirconium in the presence of any of the following elements - uranium, titanium, niobium, tantalum, molybdenum, tungsten, lead, iron, copper and tin.     

The determination of microgram quantities of fluoride: The use of the aluminium-eriochromecyanin complex

A spectrophotometric method for determining fluoride using the aluminium-eriochromecyamn complex is described. Fluoride in solutions free from mterfering ions,or obtained by distillation as hydrofluosilicic acid is determined by its destruction of the complex, the amount destroyed being directly proportional to the fluoride content. The method will detect as little as 0.02 μg/ml of fluoride and with 0–20 μg in the final solution fluoride can be determined with accuracy of ± 0.6 μg.A preliminary study of the aluminium-eriochromecyanin-fluoride system, has been carried out and a tentative reaction mechanism suggested.     

Simultaneous microdetermination of sulfur and phosphorus in organic compounds

A simple method for the simultaneous determination of sulfur and phosphorus in 3–8 mg organic sample is presented. Following oxidative combustion by the oxygen flask method, sulfate is precipitated by addition of a known amount of Ba(II) and the excess of the latter is measured polarographically. After filtration, the quinoline phosphomolybdate method is used to precipitate phosphate; the unreacted Mo(VI) is determined polarographically. The mean relative error for 13 determinations was 2.99% for S and 4.07% for P; the mean relative standard deviation was 1.43 and 4.19%, respectively.     

EDTA滴定法测定含锌物料中氧化锌

采用氯化铵-氨水体系溶解试样,干过滤后,向移取的滤液中加入氯化钡和硫酸共沉淀铅离子,过滤分离硫酸铅沉淀,向滤液中加人抗坏血酸、氟化钾、硫代硫酸钠等掩蔽剂掩蔽少量干扰元素。在pH=5~6的乙酸-乙酸钠缓冲溶液中,以二甲酚橙为指示剂,用EDTA标准滴定溶液滴定测得结果为氧化锌、水溶性锌和镉合量,扣除由原子吸收光谱法测得的水溶性锌量和镉量,即为氧化锌量。对总氨浓度、氯化铵-氨水浓度比、溶液加入量、搅拌时间、共存离子干扰、精密度等进行了实验,建立了EDTA滴定法测定含锌物料中氧化锌物相的分析方法。实验证明,氧化锌含量在24%~83%时,方法精密度(RSD)为0.25%~0.54%,加标回收率在99%~104%,完全满足含锌物料中氧化锌的测定要求。     

Sulfation and Desulfation Mechanisms on Pt–BaO/Al2O3 NOx Storage-Reduction (NSR) Catalysts

NO_x storage-reduction (NSR) catalyst is regarded as the promising solution to effectively remove NO_x emitted from lean-burn engines. However, sulfur poisoning remains the big obstacle for NSR technology to overcome. Here fundamental studies on NSR catalyst, especially focusing on the various characteristics of sulfur poisoning and regeneration mechanism, were reviewed. Various aspects of sulfation mechanism such as the roles of Pt and Ba, and the types of sulfate species were investigated. It was found that the desulfation of barium sulfate with H₂ resulted in the transformation into barium oxide (BaO) or barium sulfide (BaS) depending on the amount of barium loading and the sulfur loading, based on the combined temperature programmed reaction with hydrogen, Sulfur K-edge X-ray absorption near-edge spectroscopy and time-resolved X-ray diffraction results. H₂O played a critical role in converting BaS into BaO, thus promoting the desulfation by producing the additional H₂S. The overall sulfation and desulfation scheme was proposed by integrating the results obtained in this study.     

Accurate determination of sulfur at trace levels by isotope dilution mass spectrometry

Sulfur is recovered as silver sulfide which is converted to sulfur dioxide by combustion with pure oxygen at low pressure in 1 min. Isotopic analysis of as little as 40 μg of sulfur is possible with a precision better than 0.2%. The technique is applicable to materials such as Cu, Fe, Sn, ti, Zr, zircaloys and standard rocks.     

SD40硅烷偶联剂中硫含量的测定

对SD40硅烷偶联剂试样进行消解处理、加热至高氯酸冒烟,使原硅脱水凝聚形成沉淀除去,用硫酸钡重量法测定SD40硅烷偶联剂中硫的含量,此法的相对标准偏差低于0.15％,标样回收率为99.8％～100.2％。     

天然水中硫酸根的交流示波极谱滴定

在NH_4Ac溶液中加入标准Ba~(2+)溶液沉淀SO_4~(2-)用标准K_2CrO_4溶液滴定过量Ba~(2+)。过量的CrO_4~(2-)在交流示波极谱图上出现切口指示终点,间接求出天然水中SO_4~(2-)含量。     

烟气中二氧化硫及三氧化硫测定方法的研究

本文采用过氧化氢-氯化钡-钍试剂法以及80%异丙醇-氯化钡-钍试剂法分别测定了烟气中的二氧化硫及三氧化硫质量浓度,并对该方法的灵敏度、准确度以及各种影响因素进行了研究分析.本方法简单、快速、准确、便于现场监测控制.     

Potentiometric micro- and semimicro-determination of fluorine in organic compounds

Summary A method for the potentiometric micro- and semimicro-determination of fluorine in organic compounds is described. After combustion in a Vycor oxygen-flask, the fluoride is titrated potentiometrically with 0.02 M lanthanum (III) in an aqueous solution at pH 5–7. A fluoride ion-indicating electrode is used in conjunction with an expanded-scale pH meter. Results are within the ±0.3% absolute limits considered acceptable for microchemical analysis. The interference of sulfur is eliminated by its precipitation as barium sulfate. Filtration of the precipitate is not necessary. Phosphorus interferes and must be separated prior to fluorine analysis.

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Potentiometrische Mikro- und Halbmikrobestimmung von Fluor in organischen Verbindungen

Zusammenfassung Nach Verbrennung der Substanz im Sauerstoffkolben wird das Fluorid potentiometrisch mit 0,02 M Lanthan(III)-lösung bei pH 5–7 titriert. Hierbei wird eine fluoridspezifische Elektrode in Verbindung mit einem pH-Meter mit Skalendehnung verwendet. Der absolute Fehler ist kleiner als ±0,3%. Störender Schwefel wird als Bariumsulfat gefällt; Filtration ist nicht erforderlich. Phosphor muß vor der Bestimmung abgetrennt werden.

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Work performed under the auspices of the U.S. Atomic Energy Commission.     

Construction and performance of a drop cell for the nephelometric determination of sulfur dioxide

A nephelometric technique based on a liquid drop is described for the measurement of atmospheric sulfur dioxide. A 40-μl drop of barium chloride and hydrogen peroxide solution is suspended in a flowing-air sampling stream. The sulfur (IV) collected is oxidized to sulfur (VI) and finally precipitated as barium sulfate. Nephelometric detection of drop is achieved by an appropriate arrangement consisting of an optical fiber contacting the drop and a photodiode placed at 90° relative to the fiber. The design and characteristics of this drop-based gas sensor system are described. The analytical response, as photocurrent, is proportional to the product of the sampling period and the sulfur dioxide concentration. The detection limit is ca. 1.1 mg m⁻³ for a 10-min sampling time. The present technique is fairly rapid and simple, uses a small amount of reagent and is set up with low-cost equipment, making this system economically viable.     

Measurements in the ultraviolet region of apparent absorption by barium sulfate sols

Absorbance measurements in the ultraviolet have been shown to be useful for following changes with time in the average particle size of barium sulfate sols. The effects of the method of adding the barium chloride, a change in the temperature, the presence of 1.00M calcium chloride and the percentage of ethanol in the solution have been examined as a function of time. By measuring the apparent absorbance of barium sulfate sols in 10 cm cells, sulfate can be determined in the range of 2.5–10.0 μg per ml. This is a range which, in the past, has had to be handled by nephelometry.     

磷酸二氢铵转化法测定硫酸钡含量

针对目前重晶石中硫酸钡含量测定方法研究不多、进展缓慢的问题,提出了一种对重晶石预处理后测定硫酸钡的方法,采用磷酸二氢铵与重晶石在700℃发生复分解反应,将不溶于水且不溶于酸的硫酸钡转化为可溶于酸的磷酸钡盐,最后依据确定的磷钡比关系,根据总磷含量间接得到钡含量。实验结果表明,磷酸二氢铵与硫酸钡的物质的量之比为2.0,并在700℃的条件下高温煅烧,可使硫酸钡全部转化完全,形成偏磷酸钡,再经过氢氧化钠、双氧水处理,转变为正磷酸氢钡并溶于盐酸中,与喹钼柠酮试剂形成磷钼酸喹啉沉淀,根据沉淀质量可准确计算出样品中硫酸钡的含量。测定的结果准确、方法可行。对测定重晶石中硫酸钡的含量提出一种新的思路和解决方案,具有实际意义。     

Preconcentration and spectrophotometric determination of chromium(vi) in natural waters by coprecipitation with barium sulfate

A selective preconcentration of chromium(VI) is proposed for analysis of natural waters. Chromium(VI) is quantitatively separated from chromium(III) by coprecipitation with barium sulfate; salicylic acid is used as a masking agent for iron(III), aluminum(III) and chromium(III). The precipitate is fused with alkali carbonate, and the chromium(VI) in the melt is isolated with hot water and determined spectrophotometrically with diphenylcarbazide. The detection limit is 0.02 μg l^-1 the relative standard deviation for chromium(VI) in river water is less than 5%.     

Indirect Determination of Sulfate In A Nutritional Product Premix Using an Inductively Coupled Argon Plasma Spectrometer

Abstract

Inductively Coupled Argon Plasma Spectrometry (ICAP) has been used in a simple way to determine the sulfate content of a complex mixture. the method was based on the determination of excess barium after the sulfate in the mixture was selectively precipitated using a known amount of a standard barium chloride solution. the results obtained were in excellent agreement to those obtained using the conventional gravimetric method. A considerable time saving factor was also noted.     

Total Sulfur Concentration in Tissues of Control and Cadmium-Exposed Rats by Inductively Coupled Plasma Atomic Emission Spectrometry

Abstract

Total sulfur (S) concentration in biological samples was determined simultaneously with metal concentrations by inductively coupled plasma-atomic emission spectrometry (ICP).

A 0.2 g portion of liver and other tissues were wet-digested with 1.0 ml mixed acid (HNO₃ : HCLO₄ = 5 : 1, v/v) at 130 – 150 °C. The solution was concentrated to about 0.1 ml and then diluted to 5.0 ml with double distilled water. Concentration of S was determined by ICP using ammonium sulfate as a standard S compound. Sulfur and other element concentrations in an NBS standard reference material (Bovine Liver SRM 1577) were within the certified values by this method.

Concentrations of total S, cadmium (Cd), copper (Cu) and zinc (Zn) in the liver, kidney, spleen, lung, pancreas and blood serum were compared between the control and Cd-exposed rats. The three metal concentrations were increased significantly by Cd exposure. However, S concentration was not altered significantly in the liver and other tissues despite the extensive induction of metallothionein (MT) by the repeated Cd exposure. Metallothionein induced by the accumulated Cd (121 μg/g) and Zn (48 μg/g) in the liver was estimated to account for at maximum 7 % of the total S by assuming that the increased metals were all bound to MT. Concentration of S in blood serum was decreased significantly by Cd loading.