SULPHURIC ANHYDRIDE.-Of late a demand has sprung up for a more powerful acid than the monohydrate, and hence sulphuric anhydride has come to be manufactured, and is applied with great advantage in the preparation of aniline dyes and in the purification of ozokerite and other similar products, but as yet the manufacture is restricted to very narrow limits, as the cost of the article as at present made is greatly in excess of that of monohydrated acid. There is no doubt that with time such improvements will be introduced into the manufacture as will enable it to be sold remuneratively at a reduced price, when its employment will be vastly increased. At the present time, the manufacture of the anhydride on a commercial scale is in very few hands.
Letters patent have been granted to Rudolph Mused, of Silvertown, Victoria Docks, for his invention relating to the production of sulphuric acid, fuming sulphurie acid, and anhydrons sul phuric acid. In carrying out his invention he exposes sulphur to heat in oxygen, and prefers to pass the gases arising from this combustion into a gas-holder, either using such excess of oxygen as with the generated sulphurous acid will form equivalent proportions for their combination into sulphuric anhydride or sulphuric acid, or should these equivalent proportions not be perfectly attained he passes into the gas-holder such a proportion as may be necessary of the gas that may be deficient.
The required oxygen may be obtained by the decomposition of acidulated water acted upon by electricity, any of the well-known dynamo-electric engines being used for that purpose.
The gaseous eontents of the gas-holder obtained as above are then passed ovgr or through spongy platinum or platinized materials, such as asbestos, or the oxides of chromium, or of iron, or of copper, and either separately or in combination, which at a moderate temperatui e possess the property of causing the sulphurous acid and oxygen to combine so as to form anhydrous sulphuric acid. This may be condensed either alone in a suitable apparatus, or it may be dissolved in ordinary sulphuric acid, so as to form Nordhausen or fuming sulphuric acid. This process of manu facture may readily be made continuous by the employment of two gas-holders or receivers, so that whilst one is being emptied the other may be filling. The hydrogen given off (luring the de
composition of the water may be utilized for the purposes of heating, or, after being earburetted, for purposes of illumination.
Provisional protection has been obtained by Wilhelm Majert, of the firm of Majert and C,o., of Bahnhof-Schlebusch, Germany, for improvements in the manufacture of the anhydride of sulphuric acid and of the concentrated sulphmic acid. These improvements consist chiefly in the manipula tion of the retorts, their disposition and composition, and in the manufacture of the anhydride of sulphuric acid.
In arranging the retorts which aro used for the splitting up of sulphuric acid they set the unburnt retorts in the furnace, and afterwards fire the furnace ; or take retorts brought at least to red heat, and put them in the heat furnace. In the latter manner they prevent the retorts from being spoilt.
The aeriform products arising from the decomposition are drawn off hy channels situated in the bottom of the furnace, and leading therefrom either across one or more heat retorts, or directly to the refrigerators by a tube for leading away the gases. To save the retorts they place a second inside the retort of decomposition, and into this second one the sulphuric acid (which must be split up) firstly enters by an inlet tube suitably arranged above the inner retort. The liquid obtained by the refrigeration of the gases coming out of the retorts of decomposition contains much sul phurous acid, and by making this liquid hot they liberate the sulphurous aeid, and lead it back again to the mixing of gas SO2 O.
The contact action is managed in iron or copper vessels in lieu of the clay vessels hitherto used, and to ensure the stcechiometrical proportion SO2 0 they take oxide of copper, or iron, or of chromium, or mixings of these oxides one with another, in lieu of platinum or asbestos hitherto used. The mixing of gas SO2 0 escaped of the contact action, after taking from it the anhydride, will be brought anew in contact with the substance.