Crystallisation of a solid impure product

dissolve crude solid product in minimum amount of hot water - hot to ensure solution is saturated
filtered through a filter funnel to remove insoluble impurities
allow solution to cool and crystals to form - yield is lower if filtered when warm
filer off crystals using a Buchner funnel
cork to compress crystals - better drying but water not squeezed out
cold water poured through crystals to remove soluble impurities

Ionic potassium dichromate equation

Cr2O7²- + 14H^+ 6Fe²+ → 2Cr³+ +7H2O + 6Fe³+