From the 1820s the manufacture of chemicals from gas industry wastes was often taken over by independent industrial chemists who made arrangements with the gas companies to do so. Some of the methods used by these chemists is illustrated by a legal action of the early 1840s between Frank Hills and Angus Croll. Croll agreed to buy from Frank Hills only the acids he needed to make ammonia salts for which he held patents. He would then sell the salts back to Hills who would sell them to the gas companies for sale to other chemists. The pair agreed to issue licences to any other chemist or gas company who wanted to make the salts. These licensees would be required to buy the necessary acids from Hills at a higher price than that paid by Croll. Hills and Croll soon fell out and each accused the other of reneging on the agreement. Injunctions were issued, but were dismissed by the court. Then appeals were made. This pattern was to become only too familiar.
The Hills brothers were to specialise in ammonia salts - winning prizes at the 1851 Great Exhibition for them. His carbonate of ammonia was said to be 'known all over the world'. Sulphate of ammonia was exported to the West Indies to be used as manure for sugar cane.