Potassium perchlorate (CAS 7778-74-7): storage and disposal

An old jar usually lives at the back of a school oxidiser shelf, often in a box of demonstration materials from the same era. That box is the concern. Metal powders such as aluminium or magnesium, charcoal, sugar and similar items were often kept together for convenience, and this salt forms explosive mixtures with organic material and metals. Separate storage on paper is easy, but do not start rearranging an old kit box, as anything may have spilt and mixed inside it. Where the jar stands alone and clean, it belongs on non-combustible shelving in the oxidiser space, away from flammable stock, acids and alkalis. A record of what else is near it helps. If a jar is contaminated or unknown, leave it where it stands and do not open it.

Very little happens to the pure salt with age, and that is the difficulty. It takes up hardly any moisture, so white crystals from long ago can look exactly like new stock, and appearance offers no reassurance about its history. It gives few visible signs of its own. What to look for is contamination: dark specks, grey metallic dust, paper fragments or any second colour in the jar. Check also for a cracked container, a stained or faded label, and spillage in a kit box around the jar. An unlabelled white powder from an old demonstration box may be a mixture, and that needs more caution than a labelled jar. If you see any of this, do not open or move it, and ask for a specialist assessment.

This does not go through our standard collection route. It is arranged by manual enquiry, and never goes down the drain or into general waste.

It leaves after a manual enquiry, since it is not quoted online and the online quote path does not accept it. A clean labelled jar and an unknown mixture from a demonstration box are very different jobs, so say which you have. A store assessment is recommended, with a competent chemist seeing it in person. If there are warning signs, an explosives or emergency specialist may be needed. For the enquiry, list what shares its shelf or box, particularly metal powders and anything organic, and describe the label. Do not open it, move it, tidy the box or try to make it safe in the meantime. It must never go into a sink, a drain, a bin or a skip. School stock normally takes code 16 05 06*.

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.