Mr. R. NV. Wallace has secured patent rights for improvements ba the manufacture of sulphuric anhydride and Nordhausen acid, and in the concentration and refining of sulphuric acid.
Fig. 82 is an elevation partly in section of the apparatus comprising closed vessel, a condenser, and cooler, hereinafter described. Fig. 83 is a plan or top view of the said condenser. Fig. 84 is a coil of tubing. Fig. 85 is a perforated bottom fur the said close vessel. Like letters indicate lhe same parts throughout the drawing. This invention relates to the manufacture of sulphuric anhydride and Nordhausen acid, and to the concentration and purification of sulphurie and other acids. It permits the use of retorts of cheap materials of any desired size in such manufacture. It permits the division or separation of the distillates, and the delivery and transport or removal ef the anhydride in the vessel in whieh it is reeeived from the still, and the process employed in the manufacture may be continuous.
The bisulphate of soda is introduced into large retorts made of glazed plumbago or some similar preparation of earthenware, or of any other substance which will not decompose the sulphuric anhydride (SOO, or itself be decomposed into sulphurous acid (SOD and oxygen (0). The said retort is heated first to dull redness, when auy free sulphuric acid (H2SO4) and water are driven off. This water is condensed in a leaden worm, and as soon as the sulphuric anhydride commenees to appear, the passage of the gases into the leaden coil is stopped by means of a three-way cock, and they then pass into a series of receivers or Woulfe's bottles, constructed to retain none of the solid sulphuric anhydride in any of the lutes. The top of these reeeivers is detachable, so that it cau be replaced by blank plates, which are made properly tight, and the acid can thus be delivered or removed in the same receivers in which it has been eollected, thereby saving the workmen from the noxious fumes which would be given off on the exposure of the acid to the air • wlaile removing it from ono vessel to another. This process may be made continuous by intro ducing the requisite quantity of warm sulphuric acid into the retort before the neutral sulphate of soda has solidified. In this manner the bisulphate of soda is formed in the retort, and onto
produced therein Inv.] never be removed. And an absolutely anhydrous solid acid may bo ob tained without heating the Nordhausen acid (which is a combination of sulphuric acid and sul pilule anhydride) till the haler is driven off and collected, as in the usual way of manufacturing the crystals from Nordhausen acid, made from sulphate of iron, in Germany. Other bisulphates may be employed in the process, but sulphate of soda is the most manageable.
Another method of obtaining sulphuric anhydride according to this invention is by the direct combination of sulphur ous acid and oxy gen (0). This object may bo attained by dis tilling sulphuric acid of a gravity of in stills of glazed plumbago and passing tile gas through tubes of the same material heated to redness. Tito sulphuric acid is then decomposed into sulphurous acid and oxygen (0), Any of the acid or water remaining is then absorbed in scrubbers of chloride of calcium, or of pumice-stono moistened with sulphuric acid ( I Another way of obtaining the sulphurous acid and oxygen is by burning sulphur in iron or other pans by moans of an equivalent of oxygen, the admittance of oxygen being regulated by a weighted valve to ensure continuous pressure.
The direct combination of sulphurous acid and oxygen is also effected by passing these gases through glazed plumbago tubes heated to dull redness, and filled with platinized pumice, or asbestos, or with spongy platinum. These tubes are made of plumbngo glazed on the inner side ; a platinum lining is objectionable, because the great weight of the platinized pumice, asbestos, or the spongy platinum quickly causes perforations iu the piping unless the latter be of great thickness, which the present price of this metal would render very costly. The sulphuric anhydride (SOD is finally condensed in receivers as above described.