Paragraph 4 REAGENTS

Formaldehyde, 25-35% solution, filter if necessary before use.

Potassium chloride.

Sodium hydroxide, 10 M solution. Care should be taken to ensure that the sodium hydroxide is free from potassium.

Indicator solution: dissolve 0.5 g phenolphthalein in 100 ml 90% enthanol.

EDTA solution: 4 g of the dihydrated disodium salt of ethylenediaminetetra-acetic acid (EDTA) per 100 ml. Store this reagent in a plastic container.

STPB solution: dissolve 32.5 g sodium tetraphenylborate in 480 ml of water, add 2 ml sodium hydroxide solution (4.3) and 20 ml of a magnesium chloride solution (100 g of MgCl₂.6H₂O per litre). Stir for fifteen minutes and filter through a fine, ashless filter paper. Store this reagent in a plastic container.

Wash liquid: dilute 20 ml of the STPB solution (4.6) to 1 litre with water.

Bromine water: saturated bromine solution in water.