Ascorbic acid (CAS 50-81-7): storage and disposal

In a school prep room, the tub of ascorbic acid left over from vitamin C practicals is often the oldest thing on the general shelf, and it is the container that tells you most. Keep it in a dry, labelled, well organised store with the lid firmly on, and date it on arrival, because air, light and damp all change it. A window shelf or a warm cupboard is a poor place. Separate food grade supplies and supplements from laboratory stock, as the same material is sold both ways. Pharmacy and pathology stores should hold it in its labelled original container.

Clean white crystals are normal, and a yellow tint is the first sign of change. Ascorbic acid is easily oxidised by air, light and damp, so an old tub can go from yellow to brown and may cake or clump as moisture gets in. A strong colour change suggests oxidation and reduced purity, although the original label remains useful for identifying and describing the chemical waste. Other checks apply: a loose or cracked lid, a faded label, staining inside the lid and an unknown date of receipt. A tub that has browned should be capped, kept dry and listed for collection.

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.

Grouping and description matter more here than packaging. The collector lists the tub by name, so say whether the solid is white, yellowed or brown, and whether it has caked. Because it is not classified as hazardous on the sources we checked, the load is covered by a waste transfer note rather than a hazardous waste consignment note, but the description on it must still be accurate. Waste code 16 05 09 fits a laboratory stock tub, and 18 01 07 is used in a human healthcare setting. It must not go into the kitchen bin, a skip or a drain. Record the quantity and the lid condition.

Usually held as: solid.

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.