Abstract: A pulse generator is provided for energizing a coil with period bipolar current pulses for the purposes of airborne prospecting. The pulses have a generally square waveform, and the pulse generator includes a resonant DC to AC converter circuit including a DC input and an output coupled to the coil. A control circuit is provided for controlling the switching of the converter, and a resonant capacitor is connected in parallel across the DC input. A decoupling diode is provide for decoupling the resonant capacitor from the DC input when the voltage across the resonant capacitor exceeds that of the DC input. The converter includes first and second resonant charging sub-circuits, first and second resonant discharging sub-circuits, first and second freewheeling sub-circuits and first and second exponential charging sub-circuits.

Abstract: Merrill slime is contacted with a gold chloride solution to cement out gold and dissolve base metals. The separated solids are treated in a known type of process by chlorination with elemental chlorine, separation of the chlorinated solution and precipitation of gold powder by means of a reductant. The precipitation is partial and the remaining solution is used for the cementation step. The gold powder is separated and subjected to special washing techniques for the removal of adsorbed impurities. A molar ratio of Cl/Au of about 4 after chlorination is aimed at to minimise the solubility of silver chloride. After removing solid impurities this ratio is raised to ensure that any dissolved silver remains in solution when gold is subsequently precipitated.