Potassium Dichromate is a bright-red coloured crystal, and is often used as an oxidising agent. Compared to KMnO4 it is a mild oxidiser, and it is used to oxidise alcohols.
- It converts primary alcohols into aldehydes in normal conditions, but if heated under reflux, the aldehyde can be oxidised further to a carboxylic acid.
Reflux is a distillation technique involving the condensation of vapours and the return of this condensate to the system from which it originated.
- It converts secondary alcohols into ketones. Further oxidations is not possible.
- It is used to distinguish between an aldehyde an a ketone, as the orange K2Cr2O7 is turns green when reacted with an aldehyde. No reaction happens between the ketone and K2Cr2O7.