The fluorimetric determination of phosphate with thiamine

A method for the microdetermination of sulphur in organic compounds by means of combustion in a flow of oxygen is described. The oxides of sulphur are absorbed and stored on a small silver layer. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulphur as sulphur dioxide and regenerates the silver layer. The sulphur dioxide can be easily absorbed by dilute hydrogen peroxide and determined by any convenient method.     

Potentiometric argentimetric method for the successive titration of sulphide and dissolved sulphur in polysulphide solutions

Sulphide sulphur and dissolved sulphur in a polysulphide solution can be successively determined with satisfactory accuracy and reproducibility by potentiometric argentimetry in which a sulphide-selective indicator electrode is used. Before the titration, polysulphide ions need to be converted by an excess of potassium cyanide into thiocyanate and sulphide ions. The excess of cyanide ions is masked with formaldehyde and sulphuric acid, then the solution is made alkaline with ammonia and titrated with silver nitrate till the first end-point is reached (sulphide sulphur). After the acidification of the solution with sulphuric acid, the titration is continued till the second end-point is attained (dissolved sulphur).     

Coulometric argentometric determination of microamounts of sulphur in iron and steel after reduction to hydrogen sulphide with iron(II) in strong phosphoric acid medium

A coulometric method was developed for the determination of microamounts of sulphur in iron and steel. Hydrogen sulphide is quantitatively evolved by reduction with iron(II) in strong phosphoric acid medium and is titrated with electrolytically generated silver ion from a silver anode. Microamounts of sulphide (2.96–224.3 μg) in sodium sulphide standard solutions could be determined with an error of only a few percent. Sulphur in a potassium sulphate standard solution is quantitatively reduced to hydrogen sulphide and could be separated from the solution by heating and determined accurately. Trace amounts of sulphur (7–100 μg g^?1) in iron and steels could be determined with a standard deviation of 0.7–2.1 μg g^?1.     

The use of silver vanadates as absorbents for sulphur dioxide

A new solid absorbent for sulphur dioxide is described which is effective at room temperarures, and which does not absorb carbon dioxide. Exhaustion of the filling is indicated by a change in colour from green to brown.The reagent is prepared by heating molecular quantities of silver oxide and silver metavanadate together at 150° C. Evidence is given that on such treatment the two silver salts combine, forming a product having the same empirical composition as silver orthovanadate but different as regards its properties from the orthovanadate produced by the usual precipi-tation method.     

An analytical scheme for determining forms of sulphur in oil shales and associated rocks

An analytical scheme for determining various forms of sulphur in oil shales and associated rocks is presented. Acid-soluble sulphate, sulphur contained in monosulphide and in disulphide minerals, and organically-bound sulphur are all quantitatively recovered as separate fractions. Finely-ground oil-shale samples are treated in an inert atmosphere with 6M hydrochloric acid to dissolve the acid-soluble sulphate minerals and form H₂S from the decomposition of monosulphide minerals. The acid-soluble sulphate is precipitated as barium sulphate and the H₂S is collected and weighed as silver sulphide. Disulphide minerals in the solid residue from the acid treatment are reduced by an acidified Cr(II) solution in an inert atmosphere, releasing the sulphide as H₂S. The H₂S is collected as silver sulphide. An Eschka fusion oxidizes and solubilizes all sulphur remaining within the Cr(II)-treated residue. This sulphate represents organically-bound sulphur and is collected as barium sulphate. The analytical procedures have been verified by using ⁵⁷Fe Mössbauer spectroscopy. Good agreement between the chemical and Mössbauer data substantiated the sequential removal of the forms of sulphur and also demonstrated the ability of Mössbauer spectroscopy to determine the absolute quantities of iron present in specific minerals.     

Determination of total sulphur in soil and plant material

A rapid and accurate method for the determination of the total sulphur content of soil or plant material is described. The sample is heated with sodium bicarbonate and silver oxide at 550° for ₃h, and the sulphur content of the whole residue is reduced to hydrogen sulphide and determined as methylene blue. The results compare favourably with those of other methods.In routine use, at least 30 analyses may be completed in a day.     

13C NMR of organosulphur compounds: I—the effects of sulphur substituents on the 13C chemical shifts of alkyl chains and of S-heterocycles

The ¹³C NMR spectra have been determined of: (i) aliphatic compounds having at one end a functionalized sulphur atom (? SH, ? S^?, ? SMe, ? S(O)Me, ? SO₂Me and ? S⁺Me₂) and (ii) saturated sulphur heterocycles variously substituted at the S-atom . The results are discussed in terms of the familiar deshielding effects for α- and β-carbons and shielding effects for γ-carbons, exerted by the sulphur atom itself and/or by the atoms or groups of which the sulphur function is made up. The γ-effect of the S-atom appears to be nearly independent of the nature of the S-function and of comparable magnitude to that of an aliphatic carbon (?2·5 + ?3·0 ppm). Surprisingly, however, a S? CH₃ group shields the carbon in γ position with respect to CH₃ by an amount (?5·4 ppm) which is more than twice that (?2·5 ppm) exerted by the aliphatic γ-carbon on the S-CH₃ carbon itself. As to the cyclic compounds, the shieldings of the α- and β-carbons can be rationalized in terms of the conformational orientation of the substituent at sulphur, and the equilibrium distribution of the conformers. The results confirm the great value of ¹³C NMR for configurational and conformational assignment of S-heterocycles.     

Determination of benzoyl bisulphide by desulphurisation and solvolysis

Benzoyl disulphide is rapidly and quantitatively desulphurised to the monosulphide by reaction with triphenylphosphine in aqueous methanol at 25 degrees . The monosulphide reacts with methanol to form thiobenzoic acid and methyl benzoate. Benzoyl disulphide also reacts with methanol in solutions containing ammonium acetate or sodium acetate yielding thiobenzoic acid, methyl benzoate and elemental sulphur. Benzoyl disulphide and sulphur were detected by their polarographic reduction waves. Thiobenzoic acid was detected by its polarographic oxidation wave and yields were determined by amperometric silver nitrate titrations.     

2-Trifluoromethylimidazole, 2,4,5-tris (trifluoromethyl)imidazole and related compounds

2-Trifluoromethylimidazole, prepared by the reaction of imidazole-2-carboxylic acid with sulphur tetrafluoride, afforded a silver salt which reacted with organohalides (bromomethane, ethyl bromoacetate, N,N-dimethyl-2-chloroethylamine, and chloroacetonitrile) to give the corresponding N-alkylated derivatives. 2-Trifluoromethylimidazole-4,5-dicarboxylic acid was obtained by oxidation of 2-trifluoromethylbenzimidazole, and on decarboxylation gave only traces of 2-trifluoromethylimidazole; the major product was 2-trifluoromethylimidazole- 4-carboxylic acid. The di-acid and sulphur tetrafluoride gave 2,4,5-tris (trifluoromethyl) imidazole.     

碘和硫增感剂在卤化银颗粒表面的分布

碘在卤化银微晶中的含量和分布对感光度的影响引起乳剂配方设计者的广泛注意和重视.颗粒中的碘引起其内部结构和表面结构的改变,导致微晶颗粒表面化学及物理性质的改变,从而引起增感敏化斑的位置、分布以及随后潜影斑、灰雾斑的形成等一系列的变化并最终影响乳剂的感光性能.如果我们想有效地控制卤化银乳剂的感光度、灰雾、反差等一系列感光性能,必须调整卤化银乳剂颗粒的表面结构.     

Structure of the silver imidodi(sulphuryl fluoride)-benzene solvate AgN(SO2F)2·C6H6

The structure of the monobenzene solvate of silver imidodi(sulphuryl fluoride), AgN(SO₂F)₂ · C₆H₆, was determined from single crystal X-ray data. The asymmetric unit contains one quarter of the formula unit with the silver and nitrogen atoms lying at the intersection of two mirror planes; the sulphur and one of the oxygen atoms, O(2), lie on the same mirror plane. The remaining substituent at sulphur is in a general position that must be occupied equally by oxygen and fluorine and is designated as O/F (1). The bonding between silver and benzene is of a new type, in which each benzene is symmetrically η²-coordinated (Ag-C 2.490(7) Å) to each of two silver atoms to give infinite chains parallel to the c axis. A weak C(1)-H(1) ṫ O/F(1) hydrogen bond (C ṫ O/F 3.47 Å) was located, which cross-links these chains in the b direction, and probably accounts for the fact that the more electronegative fluorine atom predominantly occupies the general position.     

Simultaneous microanalytical determination of carbon,hydrogen and sulphur

Summary A microanalytical procedure for simultaneous determination of carbon, hydrogen and sulphur by combustion in a nitrogen atmosphere is described. The substance is oxidized by the thermal degradation products of silver permanganate (Körbl catalyst) which serve as a source of oxygen and as an absorbent for sulphur oxides. The carbon and hydrogen are determined by the classical methods and sulphur is converted into benzidine sulphate. The procedure is accurate, simple and quick.

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Zusammenfassung Ein mikroanalytisches Verfahren zur gleichzeitigen Bestimmung von C, H und S durch Verbrennung in Stickstoffatmosphäre wurde beschrieben. Die Substanz wird mit dem thermischen Zersetzungsprodukt von Silber-permanganat (Körbl-Katalysator) oxydiert, der als Sauerstoffdonator und als Absorbens für Schwefeloxide dient. C und H werden nach der klassischen Arbeitsweise bestimmt und S in Benzidinsulfat umgesetzt. Das Verfahren ist genau, einfach und rasch.

     

Röntgenfluorimetrische Bestimmung von Sulfidspuren im ppb-Bereich in wäßrigen Lösungen nach Austauschreaktion an dünnen Silberhalogenidschichten

Sulphide concentrations in the ppm and ppb range can be determined by X-ray fluorescence spectrometry in aqueous solutions with a volume up to 3 l. The solution to be analysed is passed through a thin layer of a silver halide precipitate whereby the sulphide ions are held back as silver sulphide. The membrane filter with the silver halide deposit is directly used for measuring the X-ray intensity from sulphur. The experimental conditions used include: 2?=23.20°, KAP, X-ray tube with a chromium anode, 50 kV, 40 mA, and a throughflow proportional counter. Interferences of numerous accompanying components were investigated as well as the stability of solutions with very low sulphide concentrations. These solutions can be stabilized sufficiently with ascorbic acid at pH 12, but in the case of natural water only in presence of zinc ions. The method is applicable to sulphide amounts greater than 0.1 μg. The variation coefficient for sulphide amounts of ≈ 10 μg was found to be 2.3%.     

卤化银微晶体灰雾显影的研究

本文研究了卤化银乳剂经硫、金化学敏化后在D-19b和CD-4为显影剂的显影液中的灰雾显影。实验结果表明,经硫、金敏化的乳剂在D-19b显影液中灰雾显影所产生的密度均比在CD-4显影液中灰雾显影所产生的密度大。在D-19b显影液中一些硫敏化乳剂比金敏化乳剂灰雾显影密度大,但这些硫敏化乳剂在CD-4显影液中的灰雾显影密度却比同一金敏化乳剂的灰雾显影密度小。这些实验结果与硫、金敏化的两种乳剂分别在D-19b和CD-4显影液中灰雾显影动力学研究的结果完全一致。灰雾显影动力学的实验结果指出,硫、金化学敏化在D-19b和CD-4显影液的灰雾显影中对灰雾形成的影响有显著的区别。在D-19b显影液中硫敏化乳剂比金敏化乳剂灰雾显影的速度常数大,活化能低,而在CD-4显影液中则相反,硫敏化乳剂比金敏化乳剂灰雾显影的速度常数小、活化能高。     

Determination of low levels of cyanide with a silver/silver sulphide wire electrode

A silver/silver sulphide electrode is prepred quickly by holding a cleaned silver wire in vapours from molten sulphur. In 1000–10 mg l^?1 cyanide solutions, the electrode exhibits a linear E/log C_CN function which becomes slightly sinusoidal for 10–0.1 mg l^–1 cyanide. The average slope is slightl super-Nerstian (10 mV/decade concentration). The applicability of the electrode is demonstrated for the determinations of microgram quantities of water-soluble cyanide from the Prussian blue pigments which are constituents of externally applied cosmetics. The home-made electrode provides results agreing with those obtained with commercially available electrodes.     

Nucleophilic substitution at sulphonyl sulphur part 3. Hydrolysis of substituted thiophene-2-sulphonyl chlorides catalysed by silver nitrate and silver nitrite salts

Hydrolysis reactions of substituted thiophene-2-sulphonyl chlorides (5-methyl, 5-H, 5-chloro, 5-nitro) catalysed by silver nitrate and silver nitrite salts have been studied in water at 25°. Salt effects by potassium nitrate, sodium perchlorate and mercuric bromide have also been investigated. For the catalysis effected with silver nitrate, the pseudo-first order rate constants depend on the first power of silver ion concentration, while nitrate anion is not involved in the transition state. The corresponding curved Hammett plot suggests a transition state with a partially developed sulphonylium character. With silver nitrite, the rate dependence on both silver and nitrite ion concentrations would indicate that silver is involved in the transition state as well as nitrite. Also, in this case the curved Hammett plot obtained suggests a partial positive charge on the sulphur atom in the transition state. A comparison with uncatalysed hydrolysis reactions would support a previous interpretation that thiophene-2-sulphonyl chlorides hydrolyze by an S_N2 type mechanism which can shift toward an S_N1 or an S_AN process depending on the ring substituent.     

Mechanisms of antioxidant action. The behaviour of sulphur dioxide in autoxidizing systems

Sulphur dioxide shows both chain-breaking and peroxide decomposing functions in autoxidizing systems. In a hydroperoxide initiated oxidation, it also shows a pro-oxidant effect at molar ratios (hydroperoxide to sulphur dioxide) of ?1. This reaction results in the formation of sulphur trioxide which is shown to be the true catalyst for peroxide decomposition. Sulphur trioxide is hydrated by water formed by dehydration of oxidation products and becomes less active as a catalyst as a result of phase separation.     

1H and 13C NMR studies of binuclear lanthanide(III):—silver(I) shift or relaxation reagents: Competition between several bonding sites in olefinic,aromatic and heteroaromatic compounds

The relative abilities of weak Lewis bases to complex binuclear lanthanide(III)—silver(I) reagents were checked by inter- or intra- molecular competitions. Preferential complexation at one particular site was shown to be determined mainly by the occurrence of well localized π electrons, by the relief of strain effects or by the lack of steric hindrance. In benzofuran and methoxybenzene derivatives oxygen never interacts directly with the silver reagent and plays a role mainly through electronic effects. Unlike oxygen, sulphur in benzo[b]thiophene is the preferred site of complexation with the silver reagent. On complexation with binuclear shift reagents (lanthanide = Eu, Pr, Yb) the ¹H NMR shifts were shown to result from several mechanisms. Better insight into the precise location of the reagent is obtained in ¹³C NMR by the use of the binuclear relaxation reagent Ag(tfa)-Gd(fod)₃.     

Mass spectra of tetraselenafulvalenes,diselenadithiafulvalenes and tetrathiafulvalenes

The mass spectra of 13 heterofulvalenes are reported. The spectra show great similarities within the selenium and within the sulphur series. The main difference between the selenium and the sulphur compounds results from the more facile loss of selenium compared with sulphur, and from the first fragmentation of the molecular ion, as the selenium fulvalenes lose an alkyne molecule, whereas the sulphur fulvalenes first lose an (S?R) radical. An important feature of the spectra of the simple heterofulvalenes is the formation of a rearrangement ion by migration of a heteroatom. The mechanism was elucidated by ¹³C labelling and is discussed in detail.     

Effect of mineral fillers on thermal properties and flammability ofcis-1,4-polyisoprene vulcanizates

The effect of mineral fillers such as Ultrasil VN-3, Ze?O?Sil P-45, Aerosil 200, Frantex 8, Kaolin and precipitated calcium carbonate on the thermal properties sulphur vulcanizates ofcis-1,4-polyisoprene were studied by means of thermal analysis. It was found that the addition of a mineral filler did not change the nature of the thermal processes in isoprene vulcanizates essentially, but it distinctly affected the positions of the peaks recorded in the DTA curves. The mineral fillers affected the temperatures and rates of degradation and destruction of polyisoprene cross-linked with sulphur. The presence of a mineral filler brought about a decrease in the flammability ofcis-1,4-polyisoprene sulphur vulcanizates.