Dichromate applications

This experiment describes the application of multiwavelength linear regression to the analysis of two-component mixtures. Directions are given for the analysis of permanganate-dichromate mixtures, Ti(IV)-V(V) mixtures and Cu(II)-Zn(II) mixtures. 

Evaporators have performed successfully in a number of industrial applications. Typical materials that are processed in evaporators include Caustic Soda, Caustic Potash, Sodium Carbonate, Sodium Dichromate, Sodium Nitrate, Ammonium Nitrate, Phosphoric Acid Superacid, Potash, Urea, Glue, Glycerine,... 

Self regulating chromium The self-regulating chromium solutions were introduced to eliminate the need for maintaining the correct catalyst concentration by periodic analysis they depend on the addition of a sparingly soluble sulphate to the bath which supplies the correct amount of SO 4 automatically. Initially strontium sulphate (solubility approx. l-75g/l at 30°C and 21 g/1 at 40°C) was employed for this purpose. The strontium sulphate forms a layer on the bottom of the bath, which must be stirred from, time to time. A bath with a CrO, concentration of 250 g/1 would have a catalyst content of l 52g/l SrS04 and 4-35 g/1 of KjSiF. Potassium dichromate and strontium chromate have also found application as additives for the control of the saturation solubility of the catalyst. 

Discussion. One very important application of potassium dichromate is in a back-titration for the environmental determination16 of the amount of oxygen required to oxidise all the organic material in a sample of impure water, such as sewage effluent. This is known as the chemical oxygen demand (C.O.D.) and is expressed in terms of milligrams of oxygen required per litre of water, mg L l. The analysis of the impure water sample is carried out in parallel with a blank determination on pure, double-distilled water. 

The polarographic method is applicable to the determination of inorganic anions such as bromate, iodate, dichromate, vanadate, etc. Hydrogen ions are involved in many of these reduction processes, and the supporting electrolyte must therefore be adequately buffered. 

Both lead ion and dichromate ion yield a diffusion current at an applied potential to a dropping mercury electrode of —1.0 volt against the saturated calomel electrode (S.C.E.). Amperometric titration gives a V-shaped curve [Fig. 16.14 (C)]. The exercise described refers to the determination of lead in lead nitrate the application to the determination of lead in dilute aqueous solutions (10-3 — 10-4lVf) is self-evident. 

This complex, formerly called pyridine perchromate and now finding application as a powerful and selective oxidant, is violently explosive when dry [1], Use while moist on the day of preparation and destroy any surplus with dilute alkali [2], Preparation and use of the reagent have been detailed further [3], The analogous complexes with aniline, piperidine and quinoline may be similarly hazardous [4], The damage caused by a 1 g sample of the pyridine complex exploding during desiccation on a warm day was extensive. Desiccation of the aniline complex had to be at ice temperature to avoid violent explosion [4]. Pyridinium chlorochromate is commercially available as a safer alternative oxidant of alcohols to aldehydes [5], See Chromium trioxide Pyridine Dipyridinium dichromate See Other AMMINECHROMIUM PEROXOCOMPLEXES... 

Methyl-2-pentenal was oxidised to the acid in a process involving addition over a period into a mixture of acetic acid and sodium dichromate at 50°C. Addition of the aldehyde, effected by sucking it into the reactor by application of vacuum, was entrusted to an inexperienced operator, but was apparently too fast and the exotherm led to a runaway and eruption of the reactor contents. 

Solubilized vat Cotton, wool, cellulose, and protein fibers silk Impregnated fiber when treated with an oxidized agent usually sulfuric acid and sodium nitrite for cotton dichromate wool and silk therefore, no alkali is involved. This class is applicable to cellulose and protein fibers Dyeing, printing and wool in fast shades... 

Also the preparation of methyltriphenylphosphonium dichromate ((Ph3PMe)2Cr207) and the application of this compound as efficient, inexpensive, stable and mild reagent for coupling a variety of aliphatic and aromatic thiols and aliphatic dithiols to their corresponding acyclic and cyclic disulfides has been published <2006JSF441> 1,2-dithiane was obtained by this procedure in 90% yield. 

Poly(vinyl alcohol) is used in films, coatings, fibers, and as a viscosity modifier of a variety of aqueous systems such as certain cosmetics. Its films, formulated with dichromate salts, may be cross-linked by exposure to ultraviolet light. This property has found application in photoengraving and related fields [6],... 

A method of preparation of wide applicability is the oxidation of hydroxyl-amines with such diverse reagents as bromine water, hypobromide ions, dichromate ions, lead tetraacetate, peracids, and ferric chloride (Eq. 5). 

Chromium oxides with a minimal sulfur content are preferred for metallurgical applications. These are obtained by reacting sodium dichromate with ammonium chloride or sulfate in a deficiency of 10 mol% [3.51]. Chromium (III) oxides with a low sulfur content can also be obtained by thermal aftertreatment [3.52], Thermal decomposition of chromic acid anhydride (Cr03) yields high-purity chromium(III) oxide [3.53],... 

Mithramycin shows a completely P-linked chain of D-conflgurated saccharides. This requires a totally different approach for the synthesis which is also done by application of the DBE method. The previously obtained disaccharide 180 is P-glycosylated with the monosaccharide precursor 176 to give the trisaccharide 185. After reductive debromination (Bu3SnH), an acid deformylation deblocked the C-3" position which is oxidized with pyridinium dichromate. Nucleophilic attack at the carbonyl group by methyl lithium affords a 1 1.2 mixture of 186 and 187 none of which is the desired compound [93]. Obviously, the methyl branch is formed exclusively in the axial way. 

This test method is applicable to coal of any size but is limited by the diameter of the neck of the flask. The apparatus must be scrupulously clean [usually by a mixture of sulfuric acid and potassium dichromate, after which the apparatus is washed with distilled water and dried in an oven at about 110°C (230°F)]. The condenser should be cleaned periodically in the same manner, and the receiver should be capable of collecting up to 10 mL of water in graduations of 0.1 or 0.05 mL, with a calibration for the water-toluene meniscus. 

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