Many thanks, Trish and Jo.
My reference was for 1824. So, could the Chemistry have originally [1780's] manufactured "Glauber's salts and sal ammoniac and ivory black" based on agricultural products, as per Willett, and then later, as Mike has suggested, production turned to "distilling coal to produce tar, pitch and possibly creosote and ammonia, and pitch"? (Presumably, there were coal mines closely by.) In other words, were these very different products produced on the same site sequentially or separately, at different locations?
FYI, our man, William Bennion was born in Shotton in 1760, married at Hawarden, between 1785 and 1805 fathered children in Mancot where his wife died in 1824, at which time he was 64, and apparently still working as a labourer at The Chemistry.
Any further information or insights much appreciated.
Many thanks and best wishes
John