Methylene blue (CAS 61-73-4): storage and disposal

Keep methylene blue away from the staff kitchen and any food or drink, because it is harmful if swallowed, and away from white powders and paper stock, because the dye marks whatever it touches. Stand powder and 1% solution bottles upright on a tray that catches drips and shows blue at once. Serious eye damage is the more pressing hazard, so goggles belong where the bottle is kept, not in another room. In pharmacy and veterinary cupboards, leave containers in their outer boxes so the label stays legible and is not stained by a neighbouring leak. Date each bottle on arrival and note when it was opened.

Start with the cap and label, because methylene blue announces itself there. A blue ring around the neck, a stained label or blue marks on the shelf below mean the seal has been leaking or the bottle has been handled with dirty gloves. The dye is so dark that even slight seepage looks dramatic, so a stain points to a loose cap rather than to spoilage. Powder that has become lumpy or damp shows moisture got in. A solution with a dried crust at the neck or a visibly lower level has lost water through a poor seal. Beyond these the substance gives few reliable signs of age, so a missing label or unknown date decides more than colour.

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.

The code that fits a school or university prep room is 16 05 06*, a pathology lab or hospital pharmacy clearing stock uses 18 01 06*, and a veterinary practice uses 18 02 05*. Say which setting the stock came from, because the code follows the place and not the dye. List powder and 1% solution as separate lines and flag any bottle that is leaking or stained, so it can be packed in a sealed outer container with compatible items. Pouring leftover solution down a sink is not allowed however weak it looks, and nobody should try to bleach it or otherwise treat it first.

Usually held as: solid, 1% solution.

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.