Honestly......I would charge the guy to remove it...it is a hazardous material.....you would be going him a big favor by relieving him of it....but....if you were to flip him some cash.....$50 is fair....be careful some states require that you have a safety data sheet of the material on hand if you are storing it,,,,,I know for a fact AZ dose require you to have a safety data sheet on hand for any hazardous material.......I.e. Mercury Nitric acid and other harmful products
that's my 2 penny's worth....
I have had nitric acid and mercury for many yrs in Az and don't even know what a safety data sheet is ( really don't care either). They are no more hazardous than many other readily available chemicals ....IE drain cleaners, battery acid in your car How about ammonia and sodium hypochlorite (house hold bleach) chlorine gas IS dangerous. Just because some overpaid Gov. bureaucrat says its too dangerous for the ignorant public to have access to.....................HE<<, Jay walking is illegal and can be dangerous too.
Thats my 2 cents worth.
db