Silver alloys cannot be refined by just melting and skimming the dross from the top–no precious metal alloy can. Silver alloys usually contain copper as a hardener, some of the new sterling used in jewelry is alloyed with other metals to keep it from tarnishing. Simply melting silver will not cause the copper to rise to the top and oxidize. Separating silver from copper requires nitric acid and should not be attempted at home. I’m not sure how some of the other alloys are refined. Furthermore a home chemist will never get scrap silver refined to .9999 or .999 fineness (pure). Also, as you brought up, what are you going to do with approximately 98% silver that you can’t do with 90% or 92.5% silver?
If you have large amounts of silver you want turned into ingots you can send your silver to a reputable refinery and trade your scrap for silver coins or stamped ingots. A few refineries I have had good dealings with, or that have good reputations in the jewelry industry, Hoover & Strong, Pease & Curren, McGuire & Strickland and North American Metals. You can find these companies on the Internet, I’m not affiliated with them except that I have sent scrap in to a couple of them. Regards, – Kestrel