164 Mr. Colqithoun on the Life and Writings [March, 



it consisted chiefly of the carbonate of lime, and this led him at 

 once to the true source of the carbonate of soda. He immediately 

 conjectured, and was soon after enabled most luminously to 

 demonstrate, that this salt originates in a double decomposition, 

 which takes place to a partial extent between the carbonate of 

 hme and the muriate of soda : it does not occur when at the 

 ordinary temperatures water impregnated with common salt 

 filters through the pores of carbonate of lime ; but Berthollet 

 showed in the most convincing manner that in this instance it is 

 the effect of the peculiar situations to which these two bodies are 

 exposed at the Natron Lakes. 



The data on which he founded his opinion were extremely 

 simple. He asserted first that there must exist a mixture of the 

 substances carbonate of lime and muriate of soda ; and this 

 mixture cannot but be formed to a certain extent so soon as the 

 water of the Lakes has evaporated, so as to leave a part of its 

 original bed dry. He asserted second, that there must exist a 

 pretty constant though irregular moistening of this mixture with 

 water. Experience proves this also to be the case. Under 

 these circumstances he showed that a portion of the muriate of 

 soda must invariably be converted into carbonate, in conse- 

 quence of a decomposition taking place between it and the car- 

 bonate of lime, the want of energy of the latter being com- 

 pensated by its proportionally greater mass. 



On this occasion our chemist was again greatly instru- 

 mental in teaching his country how to avail herself of one of 

 her most valuable resources, which had nevertheless remained 

 till now nearly unknown, and of very partial use. All the car- 

 bonate of soda consumed in her bleachfields, her glass, soap, 

 and other manufactories in such quantities, had hitherto been 

 constantly imported from abroad, or had been extracted from 

 barilla, at a comparatively greater expence. Whilst, therefore, 

 it is true that Le Blanc had the merit of first attempting in 

 France the manafacture of this substance out of the muriate of 

 soda or sea salt, yet it was only after the views furnished by 

 Berthollet, after the practical application which he made of the 

 knowledge he had acquired, that the formation of the carbonate 

 of soda from sea-salt, by processes analogous to those which 

 nature employs in Egypt, became universally practised in that 

 country. From that time, however, she has constantly supplied 

 herself from a mine wholly inexhaustible, but which she knew 

 not previously how toVork, with all the immense quantity of 

 that useful alkali which she daily consumes. To call this revenue 

 out of what had previously yielded absolutely nothing, and from 

 a quarter which remains for ever ready to furnish an abundant 

 supply, is not to give a beneficial direction to commerce, but 

 absolutely to create a national wealth. The sum of money thus 

 annually saved to France has been computed at more than 

 40,000,000 of livres. Here again the prosperity and the arts of 



