2.3.1. Flotation reagents
A high purity potassium ethyl xanthate (KEX), synthesised from re-distilled high grade chemicals and recrystallised from ethanol, was used as a flotation collector. A dilute solution of xanthate was prepared fresh each day as 0.1% w/v solution. The frother used was a commercial quality polypropylene glycol (Cytec Aerofroth 65) prepared as a 0.25% w/v solution. Analar grade sodium cyanide was prepared as a 0.5% solution. The initial pH was set using lime in the form of a 2.5% suspension by weight of Analar grade calcium hydroxide. Dilute solutions of Analar grade sodium hydroxide or nitric acid were added to maintain the pulp pH after it had been set to the test value with lime.
The flotation gas was either high purity bottled synthetic air (a synthetic mixture of O2 and N2) or high purity bottled nitrogen. Either distilled water or deoxygenated distilled water was used to
maintain the pulp level in the cell at a preset level. For the tests at
different pulp potential values, dilute solutions of laboratory grade
sodium hypochlorite (NaClO) and sodium dithionite (Na2S2O4) were
used as oxidants and reductants, respectively, to set and control the
pulp potential during flotation.