Sodium dihydrogen phosphate (CAS 7558-80-7): storage and disposal

The shelf decides how this stock goes wrong. Sodium dihydrogen phosphate and disodium hydrogen phosphate are usually kept in identical white tubs, so every label needs the full name and the date written clearly, and the two should have a gap between them. Keep the buffer stock in a dry, labelled, well organised store, away from food grade supplies. Histology and pathology labs often keep made-up buffer in bottles next to the dry salts, and these should be marked with the date and who made them. It has no particular chemical partners to separate it from.

Look first at what the powder is doing in the tub. Hard lumps or a damp cake show that moisture has entered, and the usual cause is a cap left loose. Made-up buffer bottles may turn cloudy or grow a film or floating threads, and they should not be used again. Faded handwriting on a decanted tub is the commonest real problem. Beyond these changes the salt shows few visible signs. A tub that has been topped up from another jar counts as mixed stock, and an undated jar is simply old.

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 waste code is for a non-hazardous chemical, so a waste transfer note applies and healthcare holders use their healthcare entry. It is not classified as hazardous on the sources we checked, but it remains chemical waste that must be described accurately, so the buffer stock does not go into a sink, a bin or a skip. List the dry salt and any made-up buffer separately, and give the quantity and the label state. Buffer bottles with unknown contents are described as unknown liquid. The carrier packs low hazard solids together.

Usually held as: buffer stock.

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.