in mainland China, usually appears in compound words such as kūmíngqúan 枯茗醛 “cuminaldehyde” curry gālí 咖喱 Food & drink cyanide shān'āi 山埃 Science & technology...

'hydrogen' and 硫 liú 'sulfur' (Sulfonium is 鋶/锍 liǔ, in analogy with ammonium) 醛 aldehyde 荃 quán quán 'change in the flavour of wine' or 'pickled vegetables'...