 Complete the following phrase:  The technique using dissolution with alkaline cyanide has been highly developed over recent years. It is particularly appropriate for low grade gold and silver ore processing e.g. less than 5 ppm gold but its use is not restricted to such ores. There are many environmental hazards associated with this extraction method, largely due to the high acute toxicity of the cyanide compounds involved. A major example of this hazard was demonstrated in the 