I have a Dixie Gun works, Inc. 2004 catalog. I will post the paragraph, I have never used it, so I don't have any info on its actual use.
page 666
CARTRIDGE CASE CLEANER
"A good customer of ours sent the following formula for cleaning brass cases. This is known as Liebig's solution. It will produce a matte gold finish and a sparkling clean inside.
The following materials and chemicals are needed: flaked chromic anhydride ( chromium trioxide), which we have for sale and is listed elsewhere in our catalog, magnesium sulfate in the purified form known as epsom salt, an old stainless steel spoon, a graduated guart glass measuring container, and hot water.
First you fill the container with hot water, then put in one heaped teaspoon of chromic anhydride and one heaped tablespoon of epsom salt. This will disolve readily into a dark orange solution and it is best to be respectable of this solution since it is an acid .
Now put no more than ten cases in the container and stir them around for two to four minutes, remove the cases with steel tongs and place temporarily in another container of hot water. when all the cases are finished, clean them with luke warm water and then shake out the cases to get rid of as much moisture as you can. Lay them on paper towels to dry.
I should mention that if the cases are greasy or especially dirty, you should put them in a container with a teaspoon of detergent and let set for about five minutes. Then rinse with clean hot water.
It is important to remember taht the solution should be hot and fresh. Do not immerse too many cases at the same time. A pint of Liebig's solution will clean approximately 50 cases but not any more satisfactorily. The solution becomes dark almost immediately after the first cases have been immersed. If cases become splotchy, you know you have exhausted the solution; or the tempature is too low."
Jim