Show harden cast iron parts at times it Is desirable to harden medium or dinall cast iron parts heros liow how anke a half pint of sul sui field acid two to quarts of common sal one link finif pound of saltpeter two of alual alii iiii ft pound of pruss lato slate of potash pot asli quarter pound of cyana cyanide tie of potash and dissolve inan gallons gallon 1 of soft water heat the iron fron to n cherry red tind and dip in tile colu tion it the parts are bantell very liard hard repeated beating and ollae dipping ing will be necess necessary nry |