Potassium ferricyanide (CAS 13746-66-2): storage and disposal

Contact with strong acid, or heat, decides the position. A dry general store suits it, but a shelf beside hydrochloric, nitric, sulfuric or phosphoric acid does not, and neither does a spot above a radiator. Trichloroacetic acid in a histology lab needs separating too. Light slowly changes it, so it tends to keep better in the dark or in brown glass. The name is the other trap. Ferricyanide and ferrocyanide differ by a few letters, and they get swapped on shelves and stock lists, so check the label against the colour: this one is red. Date the bottle on arrival. Separate it from iron salts as well, because blue stains around a shelf usually mean the two have met.

Sound stock is dark red crystals that may leave an orange-red dust on the inside of the bottle. Solutions are yellow to greenish and slowly change on standing in light. What does not look right is blue. A blue stain on the cap, label or shelf shows it has met iron salts and formed a Prussian blue type pigment, and although dramatic it mostly points to contamination or spills. Caking, a faded label or a label that disagrees with the crystal colour also deserve attention. Otherwise it gives few visual signs, and age alone does not change the handling. If the bottle has stood near acid and looks damaged or wet at the neck, leave it closed and ask for advice.

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.

Grouped with other inorganic salts, it goes into a lab pack well apart from any acid in the same collection, because strong acid can release hydrogen cyanide. That is why an accurate name matters on your list. Specialist collection is the only route, it must not go into a sink, a drain, a general waste bin or a skip, and nobody should try to treat it first. Say whether you hold the solid or a working solution, and list any used staining solution on its own line, with what else it contains. Hospital histology labs normally use code 18 01 06*, and schools and colleges 16 05 06*. Its toxicity to aquatic life makes this a hazardous waste despite its modest appearance.

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.