322 LECTURES TO SCIENCE TEACHERS. 



LECTURE II. 



ON THE ALKALI MANUFACTURE. 



THE history of the manufacture of carbonate of soda, or 

 soda-ash, from common salt is one of peculiar interest, and 

 I therefore need make no apology for bringing before you 

 the chief facts respecting the origin and growth of this im- 

 portant branch of chemical industry. 



Previous to the year 1793 the whole of the carbonate of 

 soda of commerce was obtained from the ashes of sea-plants 

 or kelp, collected on the north-west coasts of Spain, France, 

 Ireland, and Scotland. The quantity however of alkali thus 

 obtained from sea-plants was much less than that which 

 came to Western Europe from Russia and America in the 

 form of potashes, the characteristic alkali of land-plants. 



One of the first effects of the French Revolution was to 

 cut off this supply of alkali from France, and therefore to 

 diminish many important manufactures, such as the soap 

 trade, which are dependent upon its use. Under these 

 circumstances the Government of the day issued an appeal 

 to the French chemists urging the importance of obtaining 

 all the materials deposited in their own country by nature, 

 " so as to render vain the efforts and hatred of despots ; " 

 and commanding all citizens who " have commenced estab- 

 lishments or who have obtained patents for the manufac- 

 ture of soda from common salt, to make known to the 

 Convention the locality of these establishments, the quantity 

 of soda supplied by them, and the quantity they can here- 

 after supply." A commission was appointed to investigate 

 this subject ; and in 1794 they reported on thirteen different 

 processes for the manufacture of soda-ash from common salt, 

 the particulars of which had been submitted to them. The 

 preference was given to the operations devised by an apothe- 

 cary of the name of Leblanc, who had already erected a soda 

 manufactory near Paris, which had been at work some time 

 previously. 



