Sodium dodecyl sulfate (CAS 151-21-3): storage and disposal

A school prep room usually keeps this as one tub of fine white powder, often shelved with the general salts. The classification says otherwise: it is a flammable solid, so it belongs in a ventilated fire-resistant cabinet, away from ignition sources, oxidisers, acids and corrosives. University and pathology labs also hold a ready made 10% solution, which froths heavily if the bottle is shaken, so keep it upright with the cap firm. Dust is the practical problem. The powder irritates skin and the respiratory tract and can seriously damage eyes, so scoop gently and close the lid straight after each use. Date each tub on arrival, because it tends to be forgotten on a crowded shelf.

A sound tub holds a loose, dry white powder that tips freely. Damp turns it to lumps, and a tub left on a cold windowsill or in a damp cupboard may have set hard around the base. In a bottle of 10% solution, a white cloudy deposit on the bottom after a spell somewhere cold is the detergent coming back out of solution, which is worth recording but is not on its own a sign of failure. Dried froth stuck inside the neck shows that the bottle has been shaken and left. Look as well for a faded label, a crust at the cap, a cracked bottle and a tub with no date of receipt.

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

Packed in a lab pack, this flammable solid is kept apart from oxidisers, acids and corrosives, and a bottle of the 10% solution is grouped separately from the tub of powder rather than combined with it. Waste code 16 05 06* fits a school or university holder, while a hospital pathology lab would use 18 01 06*. Neither the powder nor the solution goes into a sink, a drain, a general waste bin or a skip, however mild it may look, and staff should not try to treat it first. Record the container size, whether it is powder or solution, and any residue on the outside of the pot, since a sticky, powdery exterior makes handling harder for the collection crew.

Usually held as: solid, 10% solution.

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.