Oxidation by dichromate

COD (Chemical Oxygen Demand) Legislation and controls Oxidation by dichromate... 

Then liquid ether will go thru Rg to bubbler F, where it will be partly oxidized by dichromate soln to form acetic acid... 

They nitrated radioactive toluene-l-14C with a mixture of nitric and sulphuric acid at 0°, 30°, 45° and 60°C. After nitration the whole was diluted, with water and steam distilled. Thus mononitro-products were separated from unnitrated toluene and dinitro products. The weighted sample of isomeric mononitro-toluene was diluted with a known quantity of non-radioactive m- nitrotoluene and the mixture was distilled through an efficient micro-fractionating column in order to recover a pure sample of m- nitrotoluene. The m- nitrotoluene was oxidized by dichromate-sulphuric acid mixture to m- nitrobenzoic acid and this material was radio-assayed. The proportion of m- nitrotoluene in the mixed nitrotoluenes was calculated from the formula... 

Example 29 Glycerol CH2(OH)—CH(OH)—CH2(OH) or simply C3H803 can slowly be oxidized by dichromate ions in hot acid solution. Express the equation of the reaction. 

Technical Observations. Naphthalenetetraearboxylie aeid is obtained most easily — analogously to phthalic acid — by oxidation of the corresponding higher ring system, pyrene. Instead of first chlorinating the pyrene, it can be oxidized by dichromate and sulfuric acid to form pyrenequinone (mixture of the 3,8 and 3,10 quinones) and this can then be oxidized further to naphthalenetetraearboxylie acid by chloride of lime in the presence of lime, according to the reaction ... 

Oxidation of Pulp. In the experiment reported in Figure 2, the bleached pulp stock was chemically modified prior to the formation of handsheets. The stock was first oxidized by dichromate as follows After a short period of pretreatment in a 0.2 N solution of oxalic acid at a pulp consistency of 3%, the pulp was filtered and potassium dichromate was added to yield a 0.1 N solution. The pulp was allowed to react at room temperature for 30 min and then was filtered and washed. Thereafter the oxidized pulp was soaked overnight in oxalic acid and then was filtered and washed again. 

Ozone oxidizes phenothiazine and some of its substituted derivatives to 5-oxides. Selective oxidation of V-alkylphenothiazines to 5-oxides is conveniently performed by means of sodium nitrite in acetic acid. - < In some cases, for example that of 3,7-dinitro -phenothiazine and octachlorophenothiazine, nitric acid may be used as a selective oxidant for obtaining pure 5-oxides. Chlorine oxidizes octachlorophenothiazine in nitrobenzene in the presence of water to the corresponding 5-oxide. Almost quantitative yields of 5-oxides have been reported in the oxidation of V-methylphenothia-zine, and of 10-dialkylaminoalkylphenothiazines in which there are three carbon atoms in the side chain, with ammonium persulfate " (see also Section VI, A). Some halo- and halonitrophenothiazines may be converted into 5-oxides by dichromate. - - ... 

Voiatiie compounds suoh as ethanoi or 1-butanoi provide experimentai COD vaiues from 52 to 62% of the theoretioai vaiues, which may be a resuit of the heat produoed by both the addition of suiphurio aoid to the sampie in the open oontainer and the high-temperature microzones oreated by cavitation, which wiii promote the ioss of these compounds before they are oxidized by dichromate. 

Acridine is oxidized by dichromate in acetic acid giving 9-acridone 13 and degraded by permanganate in an alkaline medium forming quinoline-2,3-dicarboxylic acid 14 ... 

Propionitrile has the general formula CH3CH2CN. Assume that it is completely oxidized by dichromate in the COD test. 

Arts. The color change from orange to green indicates that dichromate has oxidized the unknown and has itself been converted to the green-colored Cr . However, this test does not distinguish hexene from hexanol since alkenes as well as primary and secondary alcohols are oxidized by dichromate. 

The substance to be examined is changed to a colored compoxmd by the action of a reagent that does not become a part of the new entity formed. One example is test (b) for 3.19. Iodides, where identification is brought about by the violet or violet-red color produced when iodide is oxidized by dichromate to iodine. 

Most organic compounds are oxidized with the dichromate reflux method under standard procedure, but ammonia and organic nitrogen are not oxidized by dichromate in the absence of significant concentration of elemental chlorine. Flence, the dichromate reflux method is preferred over procedures using other oxidants because of its superior oxidation ability. There are, however, several potential sources of limitation in the test including the following ... 

One way of determining blood alcohol levels is by performing a titration on a sample of blood. In this process, the alcohol from the blood is oxidized by dichromate ions (Cr207 ) according to the following net ionic equation ... 

OM oxidation by dichromate and concentrated H2SO4 at 100°C with a reflux according to protocols that may comply with an AFNOR, ASTM or other standard. 

It was concluded that the leucoemeraldine form of PANI is oxidized by dichromate ions. By applying an electrode potential of Erhe = +0-2 Y, PANI film is reduced to its initial leucoemeraldine form. As a result, a net electroreduction of dichromate takes place at the PANI-modified electrode, wherein the PANI film acts as an electrocatalyst in the reaction sequence presented. Because PANI is present in its reduced form (as seen from spectra of Fig. 53, middle), it was concluded that a chemical redox reaction between dichromate and PANI is the rate-determining step, whereas the cathodic reduction of the PANI film proceeds relatively fast. 

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