Hydrofluoric acid (CAS 7664-39-3): storage and disposal

Glass, silica gel, silicon dioxide and sodium silicate must stay well away, because it attacks silicates and gives off a toxic gas as it does so. That rules out glass bottles entirely: plastic containers only. In a university store it sits low down in the ventilated corrosive area on an acid-resistant tray, away from alkalis. Its fumes attack metal as well as glass, so a spot beside glassware or metal fittings is a poor one. Dental stock is usually a small pack of etch gel. The gel is weaker but stays hazardous, so it needs a labelled, secure place and should never lie loose in a surgery drawer. Calcium gluconate gel is the usual first aid item, so check one is held where the acid is used and is within its date.

Start with the plastic itself and the label on it. Bulging or brittle plastic, a cracked cap or a crust at the neck all count as warning signs, and an unreadable label leaves stock that cannot be described properly. Then look at what surrounds the container. Cloudy or etched glass nearby, such as a frosted cabinet door or reagent bottle, points to fumes escaping, and so does corrosion on metal fittings. The liquid gives few visual signs of its own, and old stock can look just like new. A glass bottle holding this acid is a serious finding in its own right. Where any of these signs appear, leave the container untouched and ask for a specialist to look at it. Pain from skin contact may be delayed, so nobody should handle it to get a closer look.

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

It must never go into a sink, a drain, a general waste bin or a skip, and no attempt should be made to treat it first. Specialist collection, with a registered carrier delivering to a permitted site, is the only route. Say what strength the label gives, and whether it is a laboratory solution in plastic or a dental gel. Mention any cracked, brittle or bulging container, since that affects how it can be packed. Glass containers elsewhere in a collection are the awkward part, as this acid has to be grouped so that it cannot reach them. University stock usually takes the code 16 05 06*, while hospital pathology labs and dental surgeries use 18 01 06*.

Usually held as: 40%, 48%, dental etch gel.

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.