content: You may notice that not all the MSDS labels are the same, and the labels don't mean much for what is put back in the drums for disposal. Machinists may use different kinds of acids depending on the metals, then use the mineral oil wash to clean the parts well enough to be handled. The runoff might contain anything, or nothing but oil and metal shavings. I cant think of any reason to burn out the remains unless you're trying to cover your tracks, but I could be missing something.