Sodium chloride (CAS 7647-14-5): storage and disposal

Damp salt corrodes metal shelving, which is the practical reason to keep it on plastic or coated shelves in a dry, labelled store. Sodium chloride has no particular chemical partners to keep apart from, so the job is order rather than segregation: date each tub on arrival, keep food grade salt away from laboratory stock, and never decant it into unlabelled containers. Histology and pathology benches often hold small jars beside stains and fixatives, where a splash can contaminate the stock. Pharmacies hold saline in bags and ampoules, and these should be stored separately from the solid reagent so the two are never confused.

Caking and hard lumps are the usual signs of old salt, caused by moisture, and a rust stain on the shelf under the jar shows damp has been at work for some time. Salt that has lost its label cannot be reliably identified from appearance alone. Stock accessed with wet spatulas may have absorbed moisture or become contaminated, depending on what the spatulas carried. Low hazard does not mean any jar can be treated as pure: contaminated or unlabelled salt is treated as what it may contain. Leaking or cloudy saline should be reported as suspect stock, with its identity, concentration and condition recorded where known. Bags or ampoules that can no longer be reliably identified should be described as unknown liquid.

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.

A tub of salt is not ordinary kitchen waste just because of what it is. It is not classified as hazardous on the sources we checked, but it must be described accurately, and a bin or drain is not the route. Say whether it is solid or saline, how much is held and whether the container is labelled and uncontaminated. Anything contaminated or unlabelled goes down as its possible contents. A waste transfer note covers it, and healthcare holders use their healthcare entry. The carrier packs low hazard solids and liquids separately.

Usually held as: solid, 0.9% saline.

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.