prospector bill,
The ratios that 4metals gave of 3:1 to 5:1 are volume ratios of the commercial concentrated acids as you buy them (about 30-35%, by weight, for muriatic and about 67-71%, by weight, for nitric). Don't worry about these "by weight" percentages, as long as they're somewhat within these ranges. For example, to make up 5 liters of 4 to 1 aqua regia, you would use 4 liters of 30-35%, by weight, muriatic acid and 1 liter of about 67-71%, by weight, nitric acid.
philddreamer,
Yes, you can use muriatic in HCl/Cl or to drop silver as silver chloride. For most all refining work, you can consider muriatic acid and hydrochloric acid to be the same thing.