Chrome alum (CAS 10141-00-1): storage and disposal

A practical check at the shelf is colour: dark purple, glassy crystals in a tub that has not been moved for years suggest a sound seal, while pale, powdery or damp looking contents suggest air has got in. It sits comfortably in a dry, labelled, well organised store, dated on arrival, but because it irritates skin, eyes and the airways, wear gloves and eye protection and avoid raising dust. Keep it apart from food supplies and from the other alums, which look similar. Histology stores that use it for slide work should record who last opened it.

The dodecahydrate holds a lot of water, so the change to watch is the surface of the crystals: a dull, powdery bloom on the violet means water has been lost to dry air, and a wet, sticky or caked mass means water has been taken up from damp. Violet crystals that have turned greener are worth noting on the record. Old bottled solutions that have changed colour, clouded or grown mould have stood too long. Check also for a faded label, a crust at the neck, a cracked tub and no date of receipt. Each is recorded as found.

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.

Pouring leftovers away is not an option: not into a sink, a drain, a general waste bin or a skip, and staff should not try to treat it first. Waste code 16 05 06* is the usual entry for a school or university holder, with 16 05 07* where it is a discarded inorganic chemical outside a lab pack and 18 01 06* in a human healthcare setting. Crystals and bottled solution are described and packed in separate groups. Record the container size, the amount left, the colour of the crystals and whether any solution has been made up from them.

Usually held as: dodecahydrate.

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.