On the site next to Pearson the Deptford ratebooks for 1825 record an entry under 'William Beneke. Johann Beneke was a metallurgist who had extended the family business in Hamburg through an interest in dyes. Caught up in the French wars, he had been imprisoned and escaped from the fortress at Dinan. Discharged from the army he came to Deptford in 1814 to found a verdigris works. With him came William, described as a verdigris and colour manufacturer, and Frederick, who later patented the manufacture of spelter of zinc. 'Verdigris', also called 'blue vitriol' and 'copper sulphate', was made by interleaving rags soaked in pyroligneous acid between sheets of copper. At Deptford there was no ready supply of wood or copper available, but perhaps a clue to Beneke interest in the area can be found in that he also made sulphuric acid from 'pyrites which was thrown in the river'. Maybe he was attracted to Deptford by the copperas works.
In 1828 Johann Beneke left England, leaving William at the Deptford works. Johann went to Germany to continue a distinguished career as a chemist and metallurgist. He died in 1841. It is perhaps worth briefly speculating about Beneke, about whose career in Germany nothing definite has been traced. He may well have been a member of the Silesian Jewish family who became bankers in Hamburg and who were associated with the family of the composer, Felix Bartholdy Mendelssohn. In 1842 the composer stayed at their home in Denmark Hill and his daughter married one of the sons. Mendelssohn's son, Paul, became one of the founders of the German colour company, AGFA, set up in the Berlin suburb of Rammelsburg. This is the same district in which Johann Beneke had gone to install his sulphuric acid process in 1828.
When Beneke left England he seems to left his business partly in the hands of Charles Pearson. This can be deduced because in 1833 Pearson offered to settle Beneke's account with the, Hackney based, Imperial Gas Co. and took over his contract for ammoniacal liquor. It is far from clear what Pearson and Beneke do with the gas works liquor. It was not suitable for any of the manufactures which they are known to have undertaken - sulphuric acid, colour manufacture, verdigris. They may well have attempted to develop some new, secret, processes which used ammoniacal liquor for alkali. Campbell, has outlined investigations by chemists in this period into a 'direct route to soda' through the use of brine and ammonium carbonate. A factory for this was opened in Whitechapel in 1838 by the patent holders, Harrison Grey Dyar and John Hemming. Parks too noted the use of ammoniacal liquor in this context. No connections between Dyar and Hemming and the gas industry or other chemists listed here have been traced. Dyar seems to have other engineering and chemical interests evidenced by patents in a wide field from tunnelling to manufacture of white lead and zinc.
The Deptford and Greenwich copperas works seem to have continued until the mid-1830s when the sites were gradually taken up by other users. The new Creek Bridge was built through part of the site and when Mr. Huck, the Greenwich Miser, died having fallen in the beds, he was pulled out by the bridge workers. By 1840 copperas beds were a technology marginal to the needs of industrial chemists. Old Charles Pearson had died in 1828 worth £27,000 having already left the industry. Charles Pearson Jnr, although leading a more 'gentlemanly' existence, tried very hard to diversify. Following downfall, and eventual bankruptcy he died in 1850 apparently leaving nothing.