I'd like to purify the product as much as possible, so that it can be tested in a diy dog shampoo and skin spray treatment. The coal tar offerings don't work, and am not keen on the coal tar ingredient. In addition to amines, would also like to get rid of any phenols and polycyclic hydrocarbons that are likely present too, which I think could be taken care of with a solvent like ethanol, but not sure. I understand that the big-name manufacturers use solvent extraction followed by vacuum distillation to purify their product, but I've no idea what solvent they are using, what they are taking out, nor why they need to vacuum distill. Am just attempting a diy home project to see if I can make something passable for my two mutts, but at the same time would like to see if I can simulate what the manufactures do in a lab in my garage. Thank you to you and chenbeier for your insights so far.