Never Smile at a Cacodyl

The Norton History of Chemistry, Norton, New York, pp. 210-240. 

In 1835 Friedrich Wohler called organic chemistry a primeval forest of the tropics (p. 422) and the metaphor, of an unimaginably complex living system, was seemingly an apt one. Organic compounds seemed to be isolable only from living creatures—plants and animals. Often, they had to be extracted from enormously complex matrices and were challenging to isolate pure. Even urine, a clear liquid. 

Among the early significant discoveries that helped clarify and systematize organic chemistry was the notion of a radical ( from the root ) that had its earliest origins with Lavoisier acid = radical + oxygen (where the radical could be the element sulfur whose combination with oxygen formed sulfuric acid —really 503). This crude concept was followed by much more refined studies that disclosed the existence of the cyano radical (CN). It was Scheele who first treated the pigment Prussian Blue, which consists of iron compounds of ferrocyanide [today Fe(CN)g], possibly in the presence of alkali metals or ammonia e.g.. 

This brings us to cacodyl, an early name for the awful smelling, spontaneously flammable, colorless liquid tetramethyldiarsine, obtained by heating ar-senious oxide and potassium acetated  

The cacodyl radical [(CH3)2As] also appeared to Bunsen to be a stable superatom that could be exchanged amongst other radicals. Many cacodyl compounds are explosive as well as spontaneously flammable. One of these, cacodyl cyanide [(CH3)2AsCN], exploded during Bunsen s exploratory studies, and he lost his right eye.  

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