Dichromate s. Sodium

Cone, sulphuric acid (s.g. 1.84) Potassium dichromate or sodium dichromate... 

Schnitzer s green by treating an aqueous solution of potassium dichromate with sodium phosphate and tartaric acid (Zetr and Riibencamp, 1906). 

Dichlorophosphites as reagents (s. a. Methyl phosphoro-dichloridite) 11, 467 Dichromate s. Potassium —, Sodium dichromate a,/ -Dicyanocarboxylic acid esters... 

Absolute diethyl ether. The chief impurities in commercial ether (sp. gr. 0- 720) are water, ethyl alcohol, and, in samples which have been exposed to the air and light for some time, ethyl peroxide. The presence of peroxides may be detected either by the liberation of iodine (brown colouration or blue colouration with starch solution) when a small sample is shaken with an equal volume of 2 per cent, potassium iodide solution and a few drops of dilute hydrochloric acid, or by carrying out the perchromio acid test of inorganic analysis with potassium dichromate solution acidified with dilute sulphuric acid. The peroxides may be removed by shaking with a concentrated solution of a ferrous salt, say, 6-10 g. of ferrous salt (s 10-20 ml. of the prepared concentrated solution) to 1 litre of ether. The concentrated solution of ferrous salt is prepared either from 60 g. of crystallised ferrous sulphate, 6 ml. of concentrated sulphuric acid and 110 ml. of water or from 100 g. of crystallised ferrous chloride, 42 ml. of concentrated hydiochloric acid and 85 ml. of water. Peroxides may also be removed by shaking with an aqueous solution of sodium sulphite (for the removal with stannous chloride, see Section VI,12). 

Atropine causes dilation of the pupil of the eye. A drop or two of an aqueous solution, containing 1 part in 130,000 parts of water, introduced into the eye of a cat is sufficient to produce this effect. When warmed with sulphuric acid and a small crystal of potassium dichromate, atropine develops a bitter almond odour. Evaporated to dryness on a water-bath with concentrated nitric acid, it gives a residue which becomes violet on adding a drop of sodium hydroxide solution in alcohol (Vitali s test). With a solution of mercuric chloride atropine gives a yellow to red precipitate of mercuric oxide. 

The most commonly used chromate passivation process is the Cronak process developed by the New Jersey Zinc Co. in 1936, in which the parts are immersed for 5-10 s in a solution containing 182 g/1 sodium dichromate and 6ml/l sulphuric acid. A golden irridescent film is formed on the zinc or cadmium surface. Many variants (all fairly acidic) have been developed subsequently all are based on dichromate (or chromic acid) with one or more of the following sulphuric acid, hydrochloric acid (or sodium chloride), nitric acid (or nitrate), phosphoric acid, formic acid and acetic acid. A survey by Biestek shows that several of these variants are as good as the Cronak process, although none is superior. 

Chromic oxide, Cr,03, is used as a green pigment and is often made by the reaction between NajCrjOjfs) and NH(ClfsJ to give Cr >rfs), NaCl(s), Nifg), and HjO(g). Write a balanced equation and calculate how much pigment can be made from 1.0 X 101 kg of sodium dichromate. 

This protecting group is stable to n-BuLi (THF, — 25°C), s-BuLi (Et20, -25 °C), LDA, saturated ammonium chloride solution, water, MeOH, sodium hydrogen carbonate solution (2m), pyridinium dichromate/ dichloromethane, and, surprisingly, KF.2H20/THF/H20. It is unstable to 0.1 M HC1, 1m KOH, 75% aqueous AcOH, NaBH4, and pyridinium chlorochromate/dichloromethane. 

Sodium dichromate/nitrate/nitrite/perborate/ persulphate/chlorite (=s 40% by weight)... 

Sodium dichromate, 6 522, 9 630-632 manufacture, 6 538-543 U.S. exports, 6 544t U.S. imports for consumption, 6 545t Sodium dichromateCVI) dihydrate physical properties, 6 528t Sodium dicyanamide, 8 160 Sodium diethyldithiocarbamate molecular formula, 5 713t... 

Sodium dichloro-s-triazinetrione dihydrate Sodium dichromate Sodium perborate (anhydrous)... 

Experiments—Pass hydrogen sulphide slowly into the most concentrated aqueous solution of Bindschedler s green obtainable, until after some time the colour has changed to yellowish-red. Now add dilute hydrochloric acid and the solution of 0-3 g. of sodium dichromate. Precipitate the methylene blue formed by adding zinc chloride solution. 

The first is called Tinsley s wet combustion (Tinsley, 1950), and uses a highly corrosive mixture of sodium dichromate, and concentrated perchloric and sulphuric acids. For undergraduate practical classes, the safer loss on ignition method might be considered more appropriate. 

Acridine is readily oxidized to acridone by sodium dichromate and acetic acid. Pyridin-2-one and nicotinic acid have been found to undergo oxidation to oxalic add on treatment with Fenton s reagent (69CHE563). 

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