FAMILIAR LETTERS ON CHEMISTRY. 



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 con- 

 structed, 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. 



And then, as to the process ; according to theory, one hundred pounds weight of 

 sulphur ought to produce three hundred and six pounds of sulphuric acid ; in prac- 

 tice, three hundred pounds are actually obtained ; the amount of loss is therefore 

 too insignificant for consideration. 



Again ; saltpetre being indispensable in making sulphuric acid, the commercial 

 value of that salt had formerly an important influence upon its price. It is true 

 that one hundred pounds of saltpetre only are required to one thousand pounds of 

 sulphur ; but its cost was four times greater than an equal weight of the latter. 



Travellers had observed, near the small seaport of Yquiqui, in the district of 

 Atacama, in Peru, an efflorescence covering the ground over extensive districts. 

 This was found to consist principally of nitrate of soda. Advantage was quickly 

 taken of this discovery. The quantity of this valuable salt proved to be inex 

 haustible, as it exists in beds extending over more than 200 square miles. It 

 was brought to England at less than half the freight of the East India saltpetre 

 (nitrate of potassa) ; and as, in the chemical manufacture, neither the potash nor 

 the soda were required, but only the nitric acid, in combination with the alkali, 

 the soda-saltpetre of South America soon supplanted the potash-nitre of the East. 

 The manufacture of sulphuric acid received a new impulse ; its price was much 

 diminished without injury to the manufacturer ; and, with the exception of fluc- 

 tuations, caused by the impediments thrown in the way of the export of sulphur 

 from Sicily, it soon became reduced to a minimum, and remained stationary. 



Potash-saltpetre is now only employed in the manufacture of gunpowder ; it 

 is no longer in demand for other purposes ; and thus, if Government effect a saving 

 of many hundred thousand pounds annually in gunpowder, this economy must be 

 attributed to the increased manufacture of sulphuric acid. 



We may form an idea of the amount of sulphuric acid consumed, when we find 

 that 50,000 pounds weight are made by a small manufactory, and from 200,000 to 

 600,000 pounds by a large one, annually. This manufacture causes immense sums 

 to flow annually into Sicily. It has introduced industry and wealth into the arid 

 and desolate districts of Atacama. It has enabled us to obtain platina from its 

 ores at a moderate, and yet remunerating price ; since the vats employed for con- 

 centrating this acid, are constructed of this metal, and cost from 1000Z. to 2000Z. 

 sterling. It leads to frequent improvements in the manufacture of glass, which 

 continually becomes cheaper and more beautiful. It enables us to return to our 

 fields all their potash a most valuable and important manure in the form of 

 ashes, by substituting soda in the manufacture of glass and soap. 



It is impossible to trace, within the compass of a letter, all the ramifications of 

 this tissue of changes and improvements resulting from one chemical manufacture ; 

 but I must still claim your attention to a few more of its most important and imme- 

 diate results. I have already told you, that in the manufacture of soda from culi- 

 nary salt, it is first converted into sulphate of soda. In this first part of the 

 process, the action of sulphuric acid produces primary muriatic acid to the extent 

 of one and a half the amount of the sulphuric acid employed. At' first, the profit 

 upon the soda was so great that no one took the trouble to collect the muriatic 

 acid ; indeed it had no commercial value. A profitable application of it was, how- 

 ever, soon discovered : it is a compound of chlorine, and this substance may be 

 obtained from it purer than from any other source. The bleaching power of 

 chlorine has long been known ; but it was only employed upon a large scale after it 

 was obtained from residuary muriatic acid, and it was found that in combination 

 with lime, it could be transported to distances without inconvenience. Thence- 

 forth it was used for bleaching cotton ; and, but for this new bleaching process, it 

 would scarcely have been possible for the cotton manufacture of Great Britain 

 to have attained its present enormous extent it could not have competed in price 

 with France and Germany. In the old process for bleaching, every piece must be 

 exposed to the air and light during several weeks in the summer, and kept con- 

 tinually moist by manual labor. For this purpose, meadow land, suitably situa- 

 ted, was essential. But a single establishment, near Glasgow, bleaches 1,400 

 pieces of cotton daily, throughout the year. What an enormous capital would 

 be required to purchase land for this purpose ! How greatly would it increase the 



