Patent ID: 7439070

Claim:
A method of determining a value of at least one metal to be credited to an owner of a waste containing the at least one metal of unknown composition, which method comprising receiving a bulk sample of the at least one metal-containing waste, sampling the bulk sample to yield a reduced volume sample, assaying said reduced volume sample for the at least one metal component, calculating the content of the at least one metal component in the bulk sample, crediting the owner of the waste containing the at least one metal with an agreed value for the at least one metal derived from the content of the at least one metal so determined, and passing the remaining bulk sample to a refining process to recover the at least one metal; wherein the step of sampling the bulk sample comprises dispersing the bulk sample in a liquid, stirring the resulting dispersion in a mixing tank, continuously withdrawing from the bottom section of the tank a portion of the dispersion and recycling it via a recycle loop to the upper portion of the tank such that a substantially homogeneous dispersion is obtained in at least the recycle loop, and taking a representative sample of dispersion from the recycle loop.