Iron(II) sulfate (CAS 7720-78-7): storage and disposal

The heptahydrate is a salt that reacts with air, so the lid is its main protection. Keep the cap tight after every use, with the jar in a dry, labelled, general store dated on arrival, and apart from food grade supplies. In a pharmacy cupboard it can be found among iron preparations, and the reagent jar should be moved to a chemical shelf rather than left with the medicines. Histology holders with working solutions should label them separately, because a made-up solution oxidises and is not the same stock as the crystals. Part-used jars from titration practicals should go back to the shelf closed.

Good heptahydrate is pale blue-green crystals. Air slowly oxidises it, so a jar that has been opened many times shows yellow-brown or rust-coloured crusts over the green, and in a bad case the whole contents look like brown clumps. The same colour change shows in solutions, which turn yellow to brown and may throw a brown sediment. Check the neck of the jar for brown crust, the cap for corrosion and the label for staining. A faded label and an unknown date of receipt are the usual general faults. Browned stock is still iron sulfate waste and should be described as oxidised.

By specialist collection only. It never goes down the drain or into general waste. It is normally packed in a non-regulated or low hazard laboratory pack with compatible chemicals.

Describe the colour. A jar of brown, partly oxidised iron(II) sulfate and a jar of clean green crystals are the same item on the paperwork but not in what the collection team finds, so say which you hold. Crystals, any solutions and pharmacy iron preparations are listed separately, and a hospital pharmacy should check with its responsible pharmacist before medicinal products join a collection. It is hazardous waste, with 16 05 06* the entry in a lab pack and 18 01 06* in human healthcare. It must not go into a sink, a drain, general waste or a skip, and nobody should try to treat it first.

Usually held as: heptahydrate.

Part-used bottles and full containers are both fine. Tell us the size and how many, and an estimate is enough for a first price.