268 PETER SPENCE 



no practical value, others revealed results and 

 methods of great and permanent interest ; 

 and nearly all assist in marking the progress 

 of chemical discovery in the sphere to which 

 they apply. 



One of his patents for producing Prussian 

 blue and prussiate of potash, illustrates his 

 tendency to try and utilise refuse. He em- 

 ployed the alkaline sulphates, fused them in a 

 pot, and, when in a fused state, added refuse 

 leather, and calcined them together ; then 

 lixiviated and crystallised. To the mother 

 liquors he added sulphuric acid, and converted 

 the alkalies into the sulphates. This being 

 done, he added sulphate of iron, and so 

 precipitated Prussian blue. 



In the Island of Anglesey, at the Parys 

 Mine, there are enormous heaps of refuse 

 ore, called bluestone. It contains zinc, lead, 

 copper, and a little silver, but the percentages 

 of the various metals are so low, that 

 metallurgists have failed to devise a method 

 to extract any or all of them, so as to make 

 the process a commercial success. 



To use up the abundant refuse, which is 

 found in numerous localities in many parts of 

 the world, has been one of the problems which 

 metallurgists have failed to solve. Peter 



