Familiar letters on chemistry, and its relation to commerce, physiology, and agriculture / by Justus Liebig ... ; edited by John Gardner.
- Justus von Liebig
- Date:
- 1843
Licence: Public Domain Mark
Credit: Familiar letters on chemistry, and its relation to commerce, physiology, and agriculture / by Justus Liebig ... ; edited by John Gardner. Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
14/56
![already told you, that in the manufac- ture of soda from culinary salt, it is first converted into sulphate of soda. In this first part of the process, the action of sulphuric acid produces primary mu- riatic 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 ; in- deed 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 trans- Dorted to distances without inconveni- ence. Thenceforth it was used for bleaching cotton ; and, but for this new bleaching process, it would scarcely have been possible for the cotton manu- facture of Great Britain to have at- tained its present enormous extent—it could not have competed in price with France and Germany. In the old pro- cess for bleaching, every piece must be exposed to the air and light during se- veral weeks in the summer, and kept continually moist by manual labour. For this purpose, meadow land, suita- bly situated, was essential. But a single establishment near Glasgow bleaches 1,400 pieces of cotton daily, throughout the year. What an enor- mous capital would be required to pur- chase land for this purpose! How greatly would it increase the cost of bleaching to pay interest upon this capi- tal, or to hire so much land in England ! This expense would scarcely have been felt in Germany. Beside the dimi- nished expense, the cotton stuffs bleach- ed with chlorine suffer less in the hands of skilful workmen than those bleached in the sun ; and already the peasantry in some parts, of Germany have adopted it, and find it advantageous. Another use to which cheap muriatic acid is applied, is the manufacture of glue from bones. Bone contains from 30 to 36 per cent, of earthy matter— chiefly phosphate of lime, and the re- mainder is gelatine. When bones are digested in muriatic acid, they become transparent and flexible like leather, the earthy matter is dissolved, and after the acid is all carefully washed away, pieces of glue of the same shape as the bones remain, which are soluble in hot water and adapted to all the purposes of ordinary glue, without further pre- paration. Another important application of sul- phuric acid may be adduced, namely, to the refining of silver and the separa- tion of gold, which is always present in some proportion in native silver. Sil- ver, as it is usually obtained from mines in Europe, contains, in 16 ounces, 6 to 8 ounces of copper. When used by the silversmith, or in coining, 16 ounces must contain in Germany 13 ounces of silver, in England about 14|. But this alloy is always made artificially, by mixing pure silver with the due propor- tion of the copper ; and for this purpose the silver must be obtained pure by the refiner. This he formerly effected by amalgamation, or by roasting it with lead; and the cost of this process was about 2/. for every hundred weight of silver. In the silver so prepared, about T2V0 t0 Wostn Part °f g°]d remained. To effect the separation of this by nitric hydrochloric acid was more expensive than the value of the gold ; it was there- fore left in utensils, or circulated in coin, valueless. The copper, too, of the na- tive silver was of no use Avhatever. But the joVo1-'1 Part °f g°ld> being about one and one-half per cent, of the value of the silver, now covers the cost of re- fining, and affords an adequate profit to the refiner; so that he effects the sepa- ration of the copper, and returns to his employer the whole amount of the pure silver, as well as the copper, without demanding any payment: he is amply remunerated by that minute portion of gold. The new process of refining is a most beautiful chemical operation. The granulated metal is boiled in con- centrated sulphuric acid, which dis- solves both the silver and the copper, leaving the gold nearly pure, in the form of a black powder. The solution is then placed in a leaden vessel con- taining metallic copper; this is gradu- ally dissolved, and the silver precipi- tated in a pure metallic state. The sulphate of copper is also a valuable product, being employed in the manu- facture of green and blue pigments. Other immediate results of the eco- nomical production of sulphuric acid,](https://iiif.wellcomecollection.org/image/b21136932_0014.jp2/full/800%2C/0/default.jpg)
