A couple days ago, I wrote a post (Tyger, Tyger, Copper, Copper) about the theory that the late, great British poet William Blake (1757-1827) and been killed by copper poisoning due to years of acid-etching copper plates as a print maker.
One chemist promptly wrote to raise the possibility that it might instead have been acid poisoning. Blake used nitric acid to etch his plates and exposure to that corrosive compound, he pointed out, turns the skin yellow. One symptom of Blake’s final illness was his deeply yellowed skin.
Nitric acid – sometimes called engraver’s acid – has a long and fascinating history. It was reportedly first synthesized in 800 A.D. by the Persian alchemist Jabir ibn Hayyan. Made of nitrogen, hydrogen and oxygen (HNO3), alchemists used to mix the acid with water to make a bubbling, corrosive mixture they called aqua fortis or “strong water”. They used strong water to dissolve metals, making it a rather logical choice for acid-etching copper plates for printing.
But nitric acid’s corrosive nature makes it an obvious hazard. Inhaling fumes can cause the tissues of the throat to swell so severely that people find it difficult to breathe. If swallowed, it corrodes the lining of the stomach so severely that victims begin vomiting blood. Long term exposure, such as Blake would have had, results in permanent damage to the lining of the lungs and vulnerability to dangerous respiratory infections.
And, yes, it does turn skin yellow. The acid reacts with proteins in the skin and finger nails to produce that discoloration. I’ve put a photograph here showing a residential streaking in a fingernail from nitric acid exposure. The image comes from the science focused blog Shrimp and Grits where you can find even more details about that chemical reaction.
Meanwhile, I’m now pondering whether to urge the British government to exhume William Blake. I doubt we’d find any real nitric acid evidence but metal contamination can be detected centuries later.
But is it worth it? Or would it be better to let Blake’s death remain the kind of mystery that he would have surely enjoyed.