10 FAMILIAR LETTERS ON CHEMISTRY. 



acetic acid, by the process known as the quick vinegar manufacture, depends upon 

 principles, at a knowledge of which we have arrived by a careful study of these 

 properties. 



LETTER III. 



MY DEAR SIR: 



The manufacture of soda from common culinary salt may be regarded as 

 the foundation of all our modern improvements in the domestic arts ; and we may 

 take it as affording an excellent illustration of the dependence of the various 

 branches of human industry and commerce upon each other, and their relation to 

 chemistry. 



Soda has been used from time immemorial in the manufacture of soap and glass, 

 two chemical productions, which employ and keep in circulation an immense 

 amount of capitaL The quantity of soap consumed by a nation would be no in- 

 accurate measure whereby to estimate its wealth and civilization. Of two coun- 

 tries with an equal amount of population, the wealthiest and most highly civil- 

 ized will consume the greatest weight of soap. This consumption does not 

 subserve sensual gratification, nor depend upon fashion, but upon the feeling 

 of the beauty, comfort, and welfare, attendant upon cleanliness ; and a regard to 

 this feeling is coincident with wealth and civilization. The rich in the middle 

 ages concealed a want of cleanliness in their clothes and persons, under a pro- 

 fusion of costly scents and essences, while they were more luxurious in eating 

 and drinking, in apparel and horses. With us a want of cleanliness is equiva- 

 lent to insupportable misery and misfortune. 



Soap belongs to those manufactured products, the money-value of which conti- 

 nually disappears from circulation, and requires to be continually renewed. It is 

 one of the few substances which are entirely consumed by use, leaving no product 

 of any worth. Broken glass and bottles are by no means absolutely worthless ; 

 for rags we may purchase new cloth, but soap-water has no value whatever. It 

 would be interesting to know .accurately the amount of capital involved in the 

 manufacture of soap ; it is certainly as large as that employed in the coffee trade, 

 with this important difference as respects Germany, that it is entirely derived 

 from our own soil. France formerly imported soda from Spain, Spanish soda being 

 of the best quality, at an annual expenditure of twenty to thirty millions of francs. 

 During the war with England, the price of soda, and consequently of soap and 

 glass, rose continually ; and all manufactures suffered in consequence. 



The present method of making soda from common salt was discovered by Le 

 Blanc, at the end of the last century. It was a rich boon for France, and became 

 of the highest importance during the war of Napoleon. In a very short time it was 

 manufactured to an extraordinary extent, especially at the seat of the soap manu- 

 factories. Marseilles possessed for a time a monopoly of soda and soap. The policy 

 of Napoleon deprived that city of the advantages derived from this great source 

 of commerce, and thus excited the hostility of the population to his dynasty, which 

 became favorable to the restoration of the Bourbons. A curious result of an 

 improvement in a chemical manufacture ! It was not long, however, in reaching 

 England. 



In order to prepare the soda of commerce (which is the carbonate) from common 

 salt, it is first converted into Glauber's salt (sulphate of soda). For this purpose 

 eighty pounds weight of concentrated sulphuric acid (oil of vitriol) are required 

 to one hundred pounds of common salt. The duty upon salt checked, for a short 

 time, the full advantage of this discovery ; but when the government repealed the 

 duty, and its price was reduced to its minimum, the cost of soda depended upon 

 that of sulphuric acid. 



The demand for sulphuric acid now increased to an immense extent ; and, to 

 supply it, capital was embarked abundantly, as it afforded an excellent remune- 

 ration. The origin and formation of sulphuric acid was studied most carefully ; 

 and from year to year, better, simpler, and cheaper methods for making it were 

 discovered. With every improvement in the mode of manufacture, its price fell ; 

 id its sale increased in an equal ratio. 



.Sulphuric acid is now manufactured in leaden chambers, of such magnitude that 



