Ammonium oxalate (CAS 1113-38-8): storage and disposal

Container form comes first: crystals in a tub and ready-made stain in a bottle are different items. The crystals sit in a dry, labelled store with a date on arrival, away from food grade supplies. As an ammonium salt, it must be kept apart from strong alkalis such as sodium hydroxide and potassium hydroxide, which release ammonia gas, and from chlorates, which can form unstable ammonium chlorate. Sodium nitrite is another poor neighbour, since nitrites and ammonium salts can react violently on heating. Pathology stain bottles belong on a tray at the staining bench, labelled and dated, not mixed with the dry reagents.

Dry crystals of the monohydrate show few distinctive changes, so look at the tub: caking, damp lumps, crust on the thread and a faded label. Stain bottles are different, since a stain left to stand may deposit crystals, change colour or cloud, and any such bottle should be treated as old. Spills dried on the outside of the bottle leave a crust that hides the label. Because the contents are harmful by skin contact, wear gloves for any inspection. An undated tub, or one whose contents have been mixed with another salt, is unknown stock.

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.

List crystals and stain as separate items. The laboratory chemical code covers the solid, with the discarded organic chemical variant outside a lab pack and the healthcare code for a pathology holder. Record the quantity, the container condition and the label wording, and note whether a bottle is a stain preparation. It is harmful, so it does not go to a sink, a bin or clinical waste, and nobody should try to react it with another chemical. The specialist carrier packs it away from alkalis, chlorates and nitrites.

Usually held as: monohydrate, Gram stain.

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.