If you use Nitric Acid to dissolve Sterling Silver, ( Sterling is already 92.8% pure
If you are dissolving Sterling Silver, (Sterling Silver is 92.8% pure Silver to begin with so why dissolve it?), you really don't want to convert it into Silver Chloride. Silver Chloride is difficult to work with and often renders a finished product of lesser purify than the Sterling Silver you started with. Using Copper, to plate out the Silver Nitrate solution, works; but, again, you most likely will end up with Silver that is less pure than the Sterling Silver you started with.
Dissolving the Sterling Silver, using an electrolytic Silver Cell, will yield 99.9% Fine Silver crystal, if done correctly. An Electrolytic Silver Cell is the best method, I have found, to give the most consistently pure Silver, than using chemical processes. Done properly, the Electrolytic Silver Cell, dissolves the Silver into elementary pure Silver crystal that can easily be smelted into 99.9 pure Silver ingots. The best example to follow would be found on YouTube's, SREETIPS video, tutorials. If you follow his example, you will accomplish your goal of producing 99.9 pure Silver crystal.