On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Itie application of this acid to manufactures has been much impeded by the difficulty which the preparation of its solution presents on a Large scale; for the production of sulphurous acid, as given in books, is always dangerous, especially when its solution has to be prepared in large quantities. This difficulty I have overcome by a process which I here give to the public, and which enables me to prepare thousands of gallons per day of a saturated solution. The process consists in burning sulphur in a small furnace, and conducting the acid gas through earthenware tubes, surrounded with water, so as to cool them. It is then made to ascend through a wooden column, forty feet high, and about four feet wide, filled with pumice-stone, which has been previously washed with muriatic acid, and then with water. Whilst the acid ascends through the porous pumice-stone, it meets a certain and known quantity of water descending, which dissolves the acid. By opening, more or less, a valve at the top of the column, a more or less rapid current is established. With a little care, a saturated solution runs out constantly from the bottom of the column into a confined reservoir, in which it is stored for use until required. I was led to contrive the above process from a wish to use sulphurous acid in sugar-refining, convinced that it would be far superior to the sulphate of lime (which was so strongly recommended a few years ago by M. Dumas and M. Melseus), because, that by its volatility, it would not remain in the syrups or molasses, and give them, as the sulphate does, a disagreeable taste, in consequence of the lime of the sulphate remaining in the syrup as acetate or lactate. These anticipations were not only realized, but I also found that sulphurous acid possesses two advantages for the sugar refiner : First, that it stops the fermentation of his hot liquors as they come out of the filters ; and secondly, when properly applied, it tends to prevent the re-coloration of the liquors during their concentration in the vacuum pan. In practice I found that very successful results were obtained by adding two gallons of a saturated solution of sulphurous acid to every one hundred gallons of decolorized liquor, as it left the char-f Iter, and was collected in tanks, until pumped up or run into the vacuum pan.—Professor F. Grace Calvert.
