In 1839, while employed at Brick Lane, Croll approached the Imperial Gas Company together with a Mr. Bevington. They had a new scheme for 'removing the ammonia and sulphuretted hydrogen from the gas'. For £1,000 they would supply a salt which 'could be applied to the gas making machine'. The Imperial’s Board were delighted by a suggestion that meant an improvement in purification. In the deal Croll would get the waste products to use in his chemical works and 'make a profit selling the muriate of ammonia'.
Mr. Bevington, Croll's partner, was a member of the Bermondsey leather working family. The Bermondsey leather industry was well known and very large. In the 1850s a third of the country's leather was processed there. The grand buildings of the Leather Market and a Leather Hide and Wool Exchange can still be seen in the 1990s. Colonel Samuel Bevington was to be the first Mayor of Bermondsey and his statue stands at the junction of Tower Bridge Road and Tooley Street. Croll's partner was one of the three brothers who owned Neckinger Mills, which, built as a paper mill, stand where the Neckinger river once crossed Abbey Street. In 1836 the Greenwich railway was built alongside the mill's wall and the Neckinger has disappeared underground, but the mill still provides workshops and homes long after the Bevingtons have gone. In their day Bevingtons were predominant in Bermondsey leather. In the later nineteenth century they expanded into the fringes of the chemical industry to build a 'remarkably offensive' glue works on the Erith marshes. Why were they interested in Angus Croll?
Thirty years earlier Frederick Albert Winsor had suggested that tanners might have a use for ammoniacal liquor. He said that it was ‘one of the strongest lyes for tanning skin ... cheaper and quicker and superior than bark'. In the tanning process, skins were treated with lime, dung and a solution of oak bark. In the nineteenth century it was thought that ammonia compounds might be suitable substitutes. Alum, which Croll was to manufacture, was used in a different process called 'tawing' to make white, non-waterproof, leather.
Imperial bought Croll's new purification scheme but it had been formulated up to please everyone and never really worked. It was not cheap for the gas company to run, lime was still used and the hydrochloric acid caused problems with machinery. It was 'troublesome and expensive' and soon abandoned.