1941-S

Thanks, Jim, How long do you think I should leave it in?

Is there anything else I could use to take off the blackness?

It is probably oxidation. If so, acetone is not going to help. I would try it for about 10 minutes the first time. In actuality, I have let some coins set for days at a time. In pure acetone, I have never had a problem. If you have a junk coin that has black on it, try the acetone and if it does not help, try a silver polish. My guess is it will turn bright white (don't use anything worth keeping). You will at least know what you are dealing with.

Jim

More than likely the dark discoloration is a Silver Compound. That would indicate the Silver has combined with one of many other elements to form this contamination. Silver readily combines with N, O, F, S types of elements although in combinations as a general rule. The most common and the one that is usually black is the AgNO3, Silver Nitrate. Also, it could be AgF if in an area where Fluorine is utilized such as in swimmin pools. Also, in some areas where there used to be or still is steel mills, Sulfur in the air mixes with moisture, SO or SO2 + H OH to form H2SO3 or SO4 which also attacks Silver to form Ag2(SO5)3, Silver Persulfate.
The problem is the Silver has now combined with something to form the black substance and when removed, so goes some of the Silver.
Prior to Stainless Steel Cookware, where Silver was used people used to go nuts constantly cleaning with cleaners like Tar-X.
If you have no real concern of the coins value, Tar-X will remove that stuff. And some of the Silver also.

Vaslin, were you on "Young Frankenstein"?

Jim