Potassium dichromatc

Volumetric Estimation.—Tellurium may be determined by oxidation from the tellurous to the telluric condition, using an excess of potassium dichromatc or permanganate and subsequently titrating the excess of oxidising agent with a standard solution of a suitable reducing agent.2 In order to obtain accurate results with the potassium dichromate titration, certain very definite steps in the procedure are essential, and it is necessary to control the course of the reaction, since hydrochloric and telluric acids interact with production of chlorine. 

Dichromate. Sodium dichromate, [CAS 10588-01-9], Na2Cr207 2H20. red solid, soluble, powerful oxidizing agent, and consequently a fire hazard with dry car bonaceous materials. Formed by acidifying sodium chromate solution, and then evaporating. Used (1) in matches and pyrotechnics, (2) in leather tanning and in the textile industry, (3) as a source of chromate, cheaper than potassium dichromatc. 

Acidified potassium dichromatc(VI) was used to oxidise ethanol to ethanoic acid using the apparatus in the diagram. 

The addition of potassium dichromatc to the glue is stated to make the match co.mposition gradually damp owing to the oxidation of the glue. 

U. A solution of potassium dichromatc is standardised by titration with sodium ethanedioate solution. If 47.0 ctn of the dichromate solution were needed to oxidise 25.0 cm of ethanedioate solution of concen tration 0.0925 mol dm , what is the concentration of the potassium dichromate solution ... 

Walcr-peptizable colloidal substances such as gelatin, dextrin, gum arable, and soap peptize many precipitates, and are often culled protective colloids. Gelatin in the solution prevents the precipitation of silver dichromatc upon mixing silver nitrate and potassium dichroinalc solutions. (See Condensation Processes, below.)... 

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