306 LECTUEES TO SCIENCE TE AGREES. 



on this a red-hot iron ladle was placed. The mixture of 

 sulphur and saltpetre was then thrown into this ladle, and 

 the vessel closed, in order to prevent the escape of the 

 vapours which were evolved ; these were absorbed by water 

 placed in the globe, and thus sulphuric acid was produced. 

 From the mode of its manufacture this was termed acid 

 " made by the bell," and was sold at 2s. 6d. per pound. In 

 1746 a marked improvement was introduced into the pro- 

 cess by the substitution of the glass globe by a leaden 

 vessel or chamber about six feet square. This was effected 

 by Dr. Roebuck, of Birmingham, and in 1749 works for 

 the manufacture of sulphuric acid by this process were 

 erected at Prestonpans, on the east coast of Scotland. The 

 mode of working these leaden chambers was similar to that 

 adopted with the glass globes. The charge of sulphur and 

 nitre was placed inside the chamber, then it was ignited, 

 and the door closed. After some time, when most of the 

 gases had been dissolved by the water contained on the 

 floor of the chamber, the door was opened, the remaining 

 gases allowed to escape, and the chamber then charged again. 



For many years the chambers did not exceed ten cubic 

 feet in capacity, and yet in these all the acid used in the 

 country was made, and much was exported to the Continent, 

 and known as " English sulphuric acid," a name still in use 

 to distinguish acid thus made from that obtained by distilling 

 green vitriol, and known as " Nordhausen acid," from the 

 place of its manufacture. 



The first vitriol works in the neighbourhood of London 

 were erected at Battersea by Messrs. Kingscote and 

 Walker in the year 1772, whilst eleven years later a 

 connection of the above firm established sulphuric acid 

 chambers at Eccles, near Manchester. The number of these 

 works soon increased, and in the year 1797 there were, 

 according to Mr. Mactear, no less than six or eight different 

 sulphuric acid factories in Glasgow alone, whilst England, 

 which hitherto had been a large importer, in the above year 

 exported oil of vitriol to the extent of 2,000 tons. 



The object for which much of the acid was at that period 

 employed was as a substitute for sour milk in the old 

 system of bleaching, by which at least half the time 

 needed for the bleaching operations was saved. Then 

 again a great stimulus was given about this time to the 



