I have just read a lovely message from a reader, who was revisiting Oliver Sacks’ 2005 book Oaxaca Journal, and came across his story of how Sacks always greeted his old friend, chemist and botanist David Emory. They’d had a long and satisfying conversation about arsenic sulphides, with Sacks liking the “euphonious” sulphides orpiment and realgar, which were used for vivid (and poisonous) orange and yellow paints, and Emory loving iron arsenic sulphide, mostly because it’s sometimes called mispickel (which seems to be from the German, with the pickle bit meaning either pick as in a tool or pimple) which he said his students “always took for the name of a sour maiden lady, Miss Pickle”.

From that conversation onwards, he and Emory adopted a regular three-part sulphides greeting.

“He says ‘Orpiment,’ to which I retort, ‘Realgar’ and he caps the trio with ‘Mispickel!’

Saying goodbye went the other way.

So Mispickel.

Orpiment.

Realgar!