hello George
Whitemetal is a low melt aloy with a high lead content plus tin and a few other metals. It pours very very well but benifits from centrigugal casting. It has almost no mechanical strength and for anything stressed it just wont do the job. It does how ever take very fine detail incredibly well.
The following are two examples of its uses the first as its most common use as a bearing.
http://www.hawkhurst.demon.co.uk/bearings.htm
This one is the wikipedia entry and describes it very well.
http://en.wikipedia.org/wiki/White_metal
cheers kevin