A simplified method for the amplification of iodine

The sample solution is treated so that all iodine is present in the elemental state. This iodine is extracted into chloroform and thereby separated with very high selectivity from almost any matrix. Until now, in order to apply amplification via oxidation to iodate and reaction with iodide, a reextraction into a sodium hydroxide solution was necessary. In the new procedure the organic phase is shaken with bromine water. Thereby, the iodate formed moves completely into the water phase while the bromine accumulates in the chloroform. Remaining bromine in the water is destroyed with some formic acid. No buffer is needed, because the acid establishes the correct conditions for this reaction and also that between iodate and iodide. The iodine formed in sixfold amount can now be titrated visually or photometrically with thiosulfate or subjected to a second amplification cycle. The new procedure eliminates the reextraction, and the addition of some reagents especially sodium hydroxide which is the main contributor of extraneous iodine. Thus, the blank is reduced by a factor of 10 or more and is also more constant. Iodine at lower levels (< 1 μg/ml) can be determined and with higher reliability.     

An atmospheric-pressure,argon-afterglow detector for gas chromatography

The development of an atmospheric-pressure argon-afterglow, produced from an ozonizer-type discharge tube, for element-selective, multielement detection in gas chromatography is described. Characteristic atomic emission is observed from chlorine, bromine, iodine, carbon, sulfur and phosphorus in organic compounds, with limits of detection ranging from 0.02 ng for phosphorus to 20 ng for bromine. Element-selective detection for several pesticides is demonstrated.     

The activity of NaOH buffered by silicate solids in molten sodium acetate-water at 317°C

Silica and sodium acetate are present in the steam generator tube sheet crevices of many nuclear power plants. Trace solutes in the condensate are tremendously concentrated in the crevices by boiling. Sparingly soluble sodium silicates and other solids precipitate from the crevice liquid leaving an extremely concentrated molten mixture of water, sodium acetate and other salts. The precipitates buffer the activity of sodium hydroxide in the superheated liquid that remains. The activity of NaOH corresponding to the buffers quartz/sodium disilicate and sodium disilicate/sodium metasilicate at 317°C has been determined experimentally. The sodium hydroxide content of a sodium acetate-water melt buffered by these reactions was determined bychemical analysis, and the corresponding activity of NaOH at temperature was calculated using the recently published Pitzer-Simonson Model of molten salt-water mixtures. The molten mixture of sodium acetate and water plays the role of solvent in these experiments and calculations. The free energies of formation of solid sodium silicates at 317°C were also determined. The activity of NaOH corresponding to other silicate and phosphate buffers was calculated using published thermodynamic data and estimated from phase diagrams.     

Coulometric titration of iron by electrolytically generated bromine

Iron^II reacts with bromine more smoothly in acetic acid-sodium acetate medium than in sulphuric acid medium, producing a marked potential change at the end-point. The titration curves and the reaction velocities of the reaction have been studied with regard to various compositions of the electrolytic solution. It was found that iron^IIfrom 0.01 meq to 0.1 meq could be titrated coulometrically with less than about 1% error, if the electrolytic solution contained 0.1M potassium bromate, 1N acetic acid and 0.2N sodium hydroxide.     

A mild,convenient, and inexpensive procedure for conversion of vinyl halides to alpha-haloketones

Treatment of a vinyl chloride with commercially available aqueous sodium hypochlorite solution in a 2:5 mixture of acetic acid/acetone at 0 degrees C for about 1 h cleanly leads to the corresponding alpha-chloroketone. Similarly, if a vinyl bromide is exposed to sodium hypobromite (freshly prepared from bromine and sodium hydroxide) at 0 degrees C in 2:5 acetic acid/acetone as solvent, an alpha-bromoketone is produced. This methodology has been applied to a number of vinyl chlorides and vinyl bromides, and the transformations generally proceed in high yields. The mild reaction conditions are compatible with a variety of functional groups including amides, esters, and imines.     

Automated Colorimetric Method for Total Cyanide in Water and Wastewater

Abstract

An automated benzidine-pyridine method for the analysis of total cyanide is described. Cyanides are converted to cyanogen bromide by the reaction with bromine water. Cyanogen bromide reacts with benzidine in a dilute pyridine medium to form an intense red color directly proportional to the cyanide concentration. Cyanide often is found complexed with metals. Complex iron cyanides such as ferrocyanide or ferricyanide are difficult to decompose, but the conversion is hastened with mercuric chloride and magnesium chloride in a modified Serfass distillation.¹

Hydrogen cyanide is readily formed and absorbed in sodium hydroxide.     

A facile synthesis of fluorochlorobromoacetic acid

Fluorochlorobromoacetic acid was sythesized in the sequence of four steps from 1,1,2-trifluoro-2-chloroethylene in an overall yield of approximately 25%. 1,1,2-Trifluoro-2-chloroethylene was first allowed to react with sodium methoxide to form 1,2-difluoro-1-chloro-2-methoxyethylene, which was then brominated with elemental bromine and the reaction product treated with concentrated sulfuric acid to give methyl fluorochlorobromoacetate. This compound was hydrolized with a diluted sodium hydroxide solution to fluorochlorobromoacetic acid.This paper is dedicated to Professor Karl Schlögl on the occasion of his 65th birthday with warmest personal wishes     

Organoboranes for synthesis. 10.1 the base-induced reaction of bromine with organoboranes. A convenient procedure for the conversion of alkenes into alkyl bromides via hydroboration

The reaction of trialkylboranes with bromine is greatly accelerated by base. Bromination in the presence of sodium hydroxide provides alkyl bromide along with a large amount of the corresponding alcohol. The use of sodium methoxide as a base eliminates this undesirable sidereaction and provides an improved yield of alkyl bromide. Consequently, hydroboration, followed by bromination in the presence of sodium methoxide, provides a convenient new procedure for the conversion of alkenes into alkyl bromides. The organoboranes, obtained via hydroboration of terminal alkenes, react with the utilization of all three alkyl groups attached to boron, providing nearly quantitative yields of alkyl bromides. This procedure also accommodates common organic functional groups, as demonstrated by the preparation of methyl 11-bromoundecanoate and 11-bromoundecyl acetate from the corresponding functionally substituted alkenes. Under these conditions, secondary and bulky primary alkyl groups react more sluggishly. However, a procedure involving simultaneous addition of bromine and methanolic sodium methoxide provides improved results for such derivatives. Surprisingly, the base-induced bromination of tri-exo-norbomylborane results in an inversion of configuration at the reaction center to give predominantlyendo-2-bromonorbomane. A mechanism is proposed to account for this remarkable inversion.     

Brominated and iodinated thiofluoresceins

Conditions were found for the synthesis of mono-, di-, tri-, and tetrabromo- and -iodo-substituted thiofluoresceins. Iodination and bromination of thiofluorescein with molecular iodine and bromine in 1 N aqueous sodium hydroxide gave mixtures of the corresponding 2,4,5,7-tetra- and 2,4,5-trihalo derivatives in 71/14 (Y = I) and 73/13% yield (Y = Br), respectively. In the reactions of thiofluorescein with bromine in acetic acid and with iodine in methanol at a substrate-to-halogen ratio of 1 : 2, 4,5-dibromo- and 4,5-diiodothiofluoresceins were isolated in 56 and 67% yield. Analogous reactions with equimolar amounts of the reactants produced 59% of 4-bromothiofluorescein and 51% of 4-iodothiofluorescein.     

Milligram determination of primary amides

An accurate and selective milligram procedure for the determination of primary amides is described. About 3-4 mg of sample are hydrolysed with a concentrated solution of sodium hydroxide and the resulting ammonia is distilled into dilute sulphuric acid. The ammonium sulphate thus obtained is converted into ammonium iodide by passing it through hydroxide- and iodide-form resins. This iodide is oxidised to iodate with bromine, then titrated iodometrically. Determinations carried out on a number of primary amides, ureas and thioureas show a deviation of about 0.3% from full recovery of the compounds.     

Extraction of soluble fiber from distillers' grains

The feasibility of using coproducts from dry grind corn ethanol production as a substrate for the production of soluble fiber was examined. Acid- and base-catalyzed hydrolysis experiments were performed using sulfuric acid and sodium hydroxide to partially hydrolyze hemicellulose content of whole stillage, a precursor to distillers' grains, to soluble fiber. The influences of temperature, reaction time, and hydrolyzing agent concentration on the formation of soluble fiber were studied. Soluble fiber was recovered by precipitation in a 95% ethanol solution. Results indicate that appreciable quantities of soluble fiber may be extracted using either acid- or base-catalyzed reactions. The highest yield of soluble fibers was 13.2 g per 100 g-db of treated whole stillage using one weight percent sodium hydroxide at 80oC for 1 h. HPLC analysis was used to quantify the amount of monomeric sugars which were formed during the hydrolysis procedures.     

Determination of tripolyphosphate in frozen cod and scallop adductor by ion chromatography

We introduce a method for the determination of tripolyphosphate in frozen cod and scallop adductor by using ion chromatography. The tripolyphosphate was extracted from minced cod and scallop adductor with deionized water by ultrasonic leaching, and then the proteins soluble in water were precipitated with trichloroacetic acid and removed by filtering. An ion chromatograph with an ionpac AS11-HC anion-exchange column, an ASRS (Anion Self Regenerating Suppression), a conductivity detector and a gradient pump (sodium hydroxide gradient) was used. The detection limit was below 5 mg tripolyphosphate/kg cod or scallop adductor. This method is applicable to the determination of polyphosphates in aquatic products and the procedures are easy to implement.     

Coulometric titration with air transported sample

Air transported samples of a mixture containing the analyte and a supporting electrolyte are consecutively propelled into a microconduit system through a titration cell, a coil and a detector cell. Different amounts of electrochemically generated titrant are obtained in the separate samples while they are passing through the titration cell. Various quantities of the titrant are achieved by changing the duration of the titrant generating process that is done by various time for the sample solution staying in the titration cell (different sample movement rate). The titrated sample is then homogenised in the coil and detected in an electrochemical detector cell that supplies necessary data for the analyte determination. The declared method is experimentally verified on coulometric titration of hydrochloric acid (HCl) with electrogenerated sodium hydroxide and a titration of aniline with bromine generated in a bromide solution.     

2-Phenylthio-3-bromopropene, a valuable synthon, easily prepared by a simple rearrangement

[reaction: see text] Treatment of allyl phenyl sulfide with bromine, followed by aqueous sodium hydroxide, provides a good yield of 2-phenylthio-3-bromopropene 2 via a mechanism that is elucidated by isolation of the 1,3-dibromo-2-(phenylthio)propene intermediate 7. Three uses of 2 as an annulating agent for cycloheptanone are illustrated, demonstrating that this reagent is a synthetic equivalent of acetonyl halide and an alpha-halo vinyllithium. It is also readily converted to the useful synthons 2,3-bis(phenylthio)propene 16 and 2-phenylthio-3-(phenylsulfonyl)propene 17.     

Determination of fluorine, chlorine, bromine and iodine by barrier discharge radiofrequency helium plasma.

A determination method of fluorine (F), chlorine (Cl), bromine (Br) and iodine (I) by a barrier discharge radiofrequency helium plasma-atomic emission spectroscopy was developed. A borosilicate glass was wrapped by two copper film electrodes, one of which was earthed, and the other was supplied with a radiofrequency high voltage (98 kHz, 3.2 kV), resulting in a discharge inside of the tube. An optical emission from the discharge tube was introduced to a charge-coupled device (CCD)-spectrometer through an optical fiber, and was monitored in the wavelength range of 730-960 nm. The emission lines of F (733.2 nm, 739.9 nm), Cl (833.3 nm, 837.6 nm, 858.6 nm, 894.8 nm, 912.1 nm, etc.), Br (827.2 nm, 882.5 nm, 889.8 nm, 926.5 nm, etc.) and I (905.8 nm) were observed. The linearity of the calibration was determined for F and Cl over the range of 1-10 microg, and for Br of 0.1-1 microg. The relative emission intensity was in the order of Br > I > Cl >F.     

Liquid crystalline gel with refractive index gradient of curdlan

Curdlan dissolved in aqueous sodium hydroxide was dialyzed to aqueous calcium chloride to form a gel. Transparent and turbid concentric layers observed in the gel cross section perpendicular to the long axis of the dialysis tube were identified as liquid crystalline gels with refractive index gradient and amorphous gels, respectively. The thickness of each layer was proportional to the diameter of the dialysis tube, and the gelation proceeded in proportion to the root of time. The unique pattern formation was attributed to the change of curdlan conformation and calcium-induced cross-linking resulting from a diffusion of calcium cations and hydroxide anions through the dialysis tube. It is suggested that the orderedness of the curdlan molecules decreases by the increase of the curvature of the concentric liquid crystal layers as the layer comes toward the center of the dialysis tube.     

Reductions and oxidations of iron-cyanogen compounds of copper

1. Cupric ferrocyanide is oxidized by bromine water to cupric ferricyanide. 2. Cupric ferrocyanide is soluble in disodium tartrate in presence of a small quantity of sodium carbonate. 3. Cupric ferricyanide is reduced by sodium sulfite or by sulfurous acid to cupric ferrocyanide only. 4. Cupric ferrocyanide is reduced by sodium hyposulfite (Na₂S₂O₄) to white cuprous ferrocyanide Cu₄[Fe(CN)₆].     

Qualitative and quantitative analysis of uracil anticancer drugs

Two uracil anticancer drugs can be selectively identified and estimated by means of two colour reactions. 5-Fluorouracil is treated with bromine water in borax medium, and then with 2,4-dinitrophenylhydrazine in acidic medium to give an orange-red precipitate which produces a distinctly violet solution when treated with potassium hydroxide solution. Uracil mustard, containing alkylating groups, is heated with alpha-picoline in aqueous solution. The quaternary salt thus produced is condensed in alkaline medium with sodium 1,2-naphthoquinone-4-sulphonate, giving a pink colour. The possibility of using these colour tests for the determinations of these anticancer drugs in pure and dosage forms has been studied.     

碱熔酸浸试样–碘量法测定铜冶炼白烟尘中的铜

建立碱熔酸浸试样–碘量法测定铜冶炼白烟尘中铜的方法。采用氢氧化钾–硝酸钾混合溶剂熔融试样,用盐酸浸取,以溴消除砷、锑等元素的干扰,用碘量法测定铜的含量。对滴定条件及共存元素的干扰和消除进行了验证,从而确定了最佳测定条件。实验最佳条件:4 g氢氧化钾和0.5 g硝酸钾混合溶剂;马弗炉温度650 ℃;样品称样量0.300 0 g;硫代硫酸钠标准溶液浓度0.02 mol/L。采用该实验条件,铜冶炼白烟尘中的铜测定结果相对标准偏差在0.37%~0.83%之间(n=10),样品加标回收率为98.30%~101.40%。该方法分析时间短,测定结果准确可靠,具有良好的精密度,可用于铜冶炼白烟尘中铜的测定。     

The polarographic determination of chromium in aluminum alloys

A convenient polarographic method for the determination of 0.1–0.5% of chromium in aluminum alloys is described. The alloy is dissolved in a bromine water-sodium hydroxide mixture; after suitable treatment, chromate is determined polarographically. Specific directions for the simultaneous running of a blank experiment are given ; this provision greatly improves the accuracy of the results obtained.