Reagent potassium dichromate-sulfuric acid

In its simplest form, a breath alcohol screening test consists of a sealed glass tube containing a potassium dichromate-sulfuric acid reagent impregnated on silica gel. To administer the test, the ends of the tube are broken off, a mouthpiece is fitted to one end, and the other end is inserted into the neck of a plastic bag. The person being tested then blows into the mouthpiece until the plastic bag is inflated. 

Potassium Dichromate-Perchloric Acid-Nitric Acid-Sulfuric Acid Reagent... 

Spray reagent potassium dichromate (5.0 g) dissolved in 40% (v/v) sulfuric acid (100 ml)... 

The consumption of the oxime can be checked by thin-layer chromatography on silica gel G with the solvent system chloro-form/methanol (95/5 v/v) and a spray reagent consisting of 5% potassium dichromate in 40% sulfuric acid. The oxime appears as an immediate dark spot and the aziridine as a yellow spot. The checkers observed identical mobilities (Rf 0.8) for both compounds. 

Oxidation of 1-hexanol with chromic acid (sodium or potassium dichromate in aqueous sulfuric acid) yields hexanoic acid. Use of PDC or PCC in dichloromethane is not acceptable because those reagents yield aldehydes on reaction with primary alcohols. 

A number of materials,10 water, certain organic acids, the most important of which is citric acid, and certain inorganic salts, interfere with the determination. The decarboxylation cannot be conducted in the presence of nitrates and when carbonates are present two separate determinations of carbon dioxide are necessary. The procedure is also inapplicable when oxidizing compounds which are soluble in the hot reagent are present. Another interfering substance, sulfur dioxide,01 can be eliminated by the use of a saturated, acidified (sulfuric acid) solution of potassium dichromate to wash the gases evolved by the decarboxylation procedure. 

Aliphatic nitroso compounds can be prepared from IV-alkylhydioxylamines oxidation widi bromine, chlorine or sodium hypochlorite in weakly acidic solution, reaction with potassium dichromate in acetic or sulfuric acid, and by oxidation widi yellow mercury(II) oxide in suspension in an organic solvent. Silver carbonate on Celite has also been used to prepare aliphatic nitroso compounds, such as ni-trosocyclohexane, in high yield from the corresponding hydroxylamines." Aqueous sodium periodate and tetraalkylanunonium periodates, which are soluble in organic solvents, are the reagents most commonly used for the oxidation of hydroxamic acids and IV-acylhydroxylamines to acylnitroso compounds... 

Unlike aldehydes, ketones are resistant to further oxidation. They cannot usually be oxidised by the air but can be oxidised with powerful reagents like potassium dichromate(VI) mixed with concentrated sulfuric acid, with the breaking of the carbon-riarbon chain. 

Oxidations with dichromates can be accomplished in nonaqueous media or in a two-phase system by using phase-transfer reagents. The addition of 1-phenylethanol to a slurry of potassium dichromate and Adogen 464 (methyltrialkylammonium chloride) in benzene heated at 55 °C for 15 h results in an 80% yield of acetophenone. However, 2-octanol gives only a 33% yield of the ketone after being heated at 55 °C for 24 h [651]. Other solvents suitable for the reaction are dichloromethane, chloroform, and carbon tetrachloride, but not hexane [651], Better results are obtained when the alcohol is shaken for 1 min at room temperature with a mixture of a catalytic amount (10%) of tetrabutylammonium bisulfate and sodium dichromate in dichloromethane and aqueous 3 M sulfuric acid [630. ... 

The presence of an amino group on an aromatic ring often results in oxidation of the ring to a quinone. The classical and industrial method is the treatment of anilines with potassium dichromate and sulfuric acid. Thus, aniline at room temperature is converted into p-benzoquinone in 86% yield [647], and 2,5-dimethylaniline at 80 °C gives a 55% yield of p-xyloquinone [648. A specific reagent for such oxidations is the Fremy salt, potassium nitrosodisulfonate (equation 528) [490. The oxidation of the amino group takes place even if it is acylated (equation 529) [1190. ... 

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