Potassium nitrate KNO3 or sodium nitrate NaNO3 when mixed with sulfuric acid H2SO4 will form nitric acid and potassium or sodium sulfate.
2 KNO3 + H2SO4 --> 2HNO3 + K2SO4
Silver would form silver sulfate, only very slightly soluble (mostly silver sulfate salt in bottom of beaker).
The silver sulfate is much trouble to convert back to silver or recover the silver.
So this homemade nitric is not recommended when silver is involved.
After removing as mush of the potassium salts from freezing the solution, the decanted can be distilled giving pure nitric acid in the receiver, leaving the potassium sulfates behind, if done properly, now the acid can be used for silver.
Potassium nitrate KNO3 or sodium nitrate NaNO3 when mixed with hydrochloric acid HCl form nitric acid in solution and with excess HCl form aqua regia (sodium or potassium salts here are not much problem, as they will just form NaCl or KCl salts later which are very soluble.
Silver passivates in chloride acids like HCl or aqua regia and does not dissolve the silver, it will form a silver chloride passivation layer or protective crust, and if silver was very fine as powder it can form silver chloride insoluble powders, or the silver chloride crust keeping the aqua regia from attacking the metal further, like with karat gold silver chloride crust can keep the aqua regia from being able to dissolve or attack the gold in this metal alloy.
(Although sulfates are not formed in this reaction still it is not recommended for silver, because here will can have trouble with silver chlorides).
Your asking about poor mans aqua regia, it can be used on processes where small amounts of silver are involved, or silver would be in such a state as not to cause problems, or where silver has been removed first.
You could use it similar to aqua regia it would act like aqua regia about the only difference I see is it would form more sodium or potassium chloride salts in solution if concentrated and as solution's acid is consumed by metals, or is less acidic, or when concentrated.
I would not use homemade or normal aqua regia on an alloy of silver unless its silver content was very low in proportion to the gold or other metal.
With aqua regia for best results removing base metals and silver before using it is really the best way to go, yes you can use it for less than 6K gold, but here the silver will not cause too much trouble, copper content will be low enough not to cause too much trouble, tin and other problems are not involved.
It comes down to what material your using it on, how it will react, or what problems will you have either completing the process, getting it to work successfully, or recover your valuable metals and so on.
This is where closely following processes suggested by the forum will help if you do not have a good understanding of the reactions or problems created when doing things a little different, people who went before have figured out what works and what does not and developed the best procedure some of these procedures have been developed over thousands and thousands of years, since man first started using rocks and metals to make tools, others have been developed in more recent times with thousands of people trying to find better ways by experimenting and failing, and then come back to the known procedure that works after the figure out they lost most of their gold experimenting.
it is kind of funny people with no experience want to experiment to find a better way to do things before they even know how to do things or have any understanding of what works or why, but then those with experience use the known procedures, and rarely veer far from them with their procedures
