Soap belongs to those manufactured products, the money value of which continually 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 sodas 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 wars of Napoleon.  In a very short time it was manufactured to an extraordinary extent, especially at the seat of the soap manufactories.  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 favourable 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 80 pounds weight of concentrated sulphuric acid (oil of vitriol) are required to 100 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  The duty upon salt checked, for a short time, the full advantage of this discovery; but when the Government repealed the duty, and its price was reduced to its minimum, the cost of soda depended upon that of sulphuric acid.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 remuneration. the origin and formation of sulphuric acid was studied most carefully; and from year to year, better, simpler, and cheaper methods of making it were discovered.  With every improvement in the mode of manufacture, its price fell; and its sale increased in an equal ratio.

Sulphuric acid is now manufactured in leaden chambers, of such magnitude that they would contain the whole of an ordinary-sized house.  As regards the process and the apparatus, this manufacture has reached its acme—­scarcely is either susceptible of improvement.  The leaden plates of which the chambers are constructed, requiring to be joined together with lead (since tin or solder would be acted on by the acid), this process was, until lately, as expensive as the plates themselves; but now, by means of the oxy-hydrogen blowpipe, the plates are cemented together at their edges by mere fusion, without the intervention of any kind of solder.