Originally Posted by PhotoJim
Did you know that human urine contains pyrocatechin?
Pyrogallol and pyrocatechin (or catechol as some call it) aren't all that dangerous. Reasonable care mitigates the risks.
Hydroquinone is quite dangerous too. We use it without batting an eye.
And hydroquinone is also a staining developer. Use it in place of catechol in Pyrocat HD or MC and you'll see. Not the same color, but staining nonetheless.