“The chief advantage consists in the direct conversion of salt into carbonate of soda, and next from the fact, that from a saturated brine only the sodium is precipitated, with none of the other metals of the mother liquor. Besides this, the product is absolutely free from all sulphur compounds, the soda is of a high grade, the apparatus and utensils are very simple, there is a great saving of labour and fuel, and no noxious gases and waste products are produced, which is of importance from a sanitary point of view. The only weak point of the ammonia process is the loss of chlorine, which is converted into worthless chloride of calcium.
“The effect which the general introduction of the new soda process will exert upon large chemical industries in general, and especially upon the consumption of sulphur, the manufacture of sulphuric acid, and chloride of lime, cannot be overlooked.”
3. Another method for the direct preparation of soda and potash from their chlorides is described in the ‘Bayerisches Industrie und Gewerbe Blatt.’[176] The process is thus described by its author, Herr E. Bohlig:
[176] ‘New Remedies,’ 1878, 4.
1. Magnesium oxalate (freshly prepared when newly starting, but, after the first operation,
obtained as a dry product in the next step) is allowed to drain, and then mixed in a large vat with the proper quantities of sodium chloride, or concentrated brine and hydrochloric acid, after which it is allowed to stand a few hours. Decomposition takes place almost instantaneously; all the magnesium goes into solution in form of syrupy magnesium chloride, while all the sodium and oxalic acid are deposited as a crystalline acid salt (acid sodium oxalate, or binoxalate of sodium).
Since the magnesium oxalate is always obtained of the same composition and in the same quantity, it is sufficient to determine its weight once for all, and to take each time the previously common amounts of common salt. The acid need not be weighed either; it must be added in just sufficient quantity to destroy the milky appearance which the mixture first assumes.
The reaction is as follows:
| MgC2O4 | + | HCl | + | NaCl | = | NaHC2O4 | + | MgCl2 |
| Magnesium oxalate. | + | Hydrochloric acid. | + | Sodium chloride. | = | Sodium binoxalate. | + | Magnesium chloride. |
The crystalline powder of sodium binoxalate is transferred to large draining filters, washed with water until the acid solution of magnesium chloride is removed, and worked up, as below described, while still moist.