Propylene glycol (CAS 57-55-6): storage and disposal

Read the word before glycol on the label. Propylene and ethylene glycol are both clear, syrupy liquids, and a faded or handwritten label is how one gets mistaken for the other. After that, a dry, labelled, well organised shelf is all it needs, dated on arrival, with food grade supplies kept apart from laboratory stock, which matters in a pharmacy that holds both. It absorbs moisture from the air, so keep the cap tight and the neck wiped clean. A tray under the bottle catches the sticky drips that thick liquids leave.

Little shows on a sound bottle, so there is no dramatic ageing to look for. The most likely change is moisture: propylene glycol takes up water from the air, so a much used bottle may run thinner and, if water has got in along with other matter, may look cloudy. A sticky ring around the cap, a label stained by drips and a lower level than the record are the usual signs of a poor closure. Mould or a sour smell is not expected in neat stock and suggests contamination. Record a bottle with any of these features as it stands, and if it has lost its label, record it as unknown.

We arrange this by specialist collection. We do not publish a drain or general waste route for any chemical. It is normally packed in a non-regulated or low hazard laboratory pack with compatible chemicals.

Write down the label wording as printed, the grade if there is one, the amount left and whether it is the original bottle or a decanted one. Pharmacy and clinic stock may carry a supplier batch label worth copying across. Waste code 16 05 09 usually applies to discarded chemicals not normally classified as hazardous and comes with a waste transfer note, with 18 01 07 usually used in a human healthcare setting. The producer confirms the classification. Specialist collection is the only route. It must not go to a drain or a bin, and nobody should try to treat it first.

Usually held as: neat.

Tell us the container size and how many you hold. An estimate is enough to start with, and some items cannot be priced until someone has looked at them.