and at the same time reader the mansion premises free from the insidious and dangerous gases generated in the public sewer. Mansions, &c.—already drained of their sewage by means of flatly-laid sewers, which are absolutely unsuitable on that sccount to create a certain and reliable scour of the drains leading into cesspools or public sewers-couli secare perfect flushing by using the Syphon-Ejector, and placing the bottom of it about one foot, more or less, above the head of the sewer drain, terminating at the mansion (see Figs. 13 and 11 This would in some cases (see Fig. 13) supersede the necessity of fixing a "Pneumatic Ejector” to do the work as per iliustration (Fig. 13). XXIII.-Contributions to the Technology of Sulphuric Acid.— On the Distribution and Condensation of the Gases in the Leaden Chamber. By JAMES MACTEAR, F.C,S., F.I.C., President of the Section. [Read before the Chemical Section, April 7th, 1879.] A SMALL book on the chemistry of the sulphuric acid manufacture was published in 1873, by the late Mr. H. A. Smith. It contained the results of much hard work, and gave many interesting figures. The results of a series of laboratory experiments led him to believe that the greatest amount of condensation of the sulphuric acid took place at the bottom of the chamber, and that its upper portion was of use principally as a reservoir for the gases. He therefore reasoned that the best form of chamber for the production of sulphuric acid would be one where the height was small in proportion to the length. He attempted to prove his theory by an examination of the working of a chamber actually in use, and of considerable size, its dimensions being 140 feet long, containing 105,000 cube feet of space, and capable of using about. 50 cwts. of sulphur, in form of pyrites, per 24 hours. Steam was injected at three points in the side of this chamber, as shown in plan below, and also along with the sulphurous gases entering the chamber, which they did through a pipe 3 feet in diameter. 3 ft. ་ 20' 7". 65' 7". 110' 0". He drew out of the chamber a series of samples of the gases, at points 10 feet apart from one end of the chamber to the other, and at two levels, 15 feet and 3 feet above the bottom respectively-there being thus 14 different samples at each level. The gases thus obtained were then tested for sulphurous, sulphuric, and nitric acids, and I have embodied his results in the following diagrams : The shaded portion of the diagram shows the amount of sulphurous acid existing as such at the various points of the chamber where the samples were drawn-the upper shaded portion representing the amounts found at or along the line at 15 feet from floor of chamber, the lower shaded portion those found along the line at 3 feet from floor. The effect of the introduction of the steam is well marked in the diagram by the fall in the amount of sulphurous acid found at or close to the points at which it is injected-viz., at 20 feet, 65 feet, and 110 feet from entrance of gases. This diagram, when closely examined, shows some most extraordinary results, there being little or no sulphuric acid found at 15 feet above floor of chamber for some distance from entrance of the gases, while at the 3 feet level the amount is as much as 81 per cent. There is little doubt that the injection of the steam with the gases into the chamber, through a pipe of 31 feet diameter, at a height between 15 feet and 24 feet from floor, would cause a strong current of gas, chiefly SO, inward and upward, whilst a back current would carry the partially-converted gases towards the bottom and end of the chamber, where, of course, the largest amount of SO, would naturally be found, as, no matter at what height any molecule of sulphuric acid was formed, it must pass through the lower zone of the chamber ere reaching the liquid acid upon the bottom. Regarding the amount of nitric acid (which I take to mean all the nitrous compounds calculated to nitric acid), Mr. Smith says:— "The variations in the percentage of nitric acid are not very great, being only between 3 per cent. and 26 per cent., these being the maximum and minimum amounts. It attains its greatest height at 100 feet and 110 feet from end of the chamber, and then sinks rapidly down to 3 per cent. at 140 feet." If we now examine carefully the figures represented in the diagrams, I think it will be obvious that Mr. Smith's conclusions were drawn from totally insufficient data to enable him to decide as to the distribution and action of the gases in the chamber. Tabulating his results at the two levels of 15 feet and 3 feet from floor of chamber, for sulphurous, sulphuric, and nitric acids, we have the following figures: DISTANCE IN FEET FROM ENTRANCE OF GASES. 90 100 110 120 130 140 10 20 30 40 50 60 70 80 0 80 90 72 71 46 32 25 26 30 22 29 5 22 23 13 18 18 TOTALS, 97 89 65 63 56 53 62 51 5 64.5 54 42 23 31 34 At 15 feet. On glancing at the totals in above Table it can at once be seen that the expression "percentage," as regards the various acids, requires some explanation. It is by no means clear what is meant by it, as it cannot mean percentage in the chamber gases, and certainly is not the percentage of the total acids, as one of the totals mounts up to 103 per cent., while one is as low as 23 per cent. These irregularities are quite to be looked for if the estimations of the three acids were not made in the same sample of gas, and I am inclined to believe that separate samples were used for each estimation. Owing to the constant whirling about of the gases in the chamber, caused chiefly by the mechanical force of the steam jets, it would be highly improbable that two samples, even taken at very short intervals of time, would have the same composition; and such irregular results-as these are seen to be from comparing the figures—are utterly misleading as to the composition of the gases. The variation is very marked indeed in the case of the nitric acid, which under normal conditions must go on increasing in amount, as the SO, gets converted into SO, and is removed by condensation, but which the figures as above treated shew to be very much less at the exit than at the entrance of the chamber, almost before any condensation has taken place. Vitriol makers are familiar with what is usually called the "going through" of a series of chambers. By this technical expression is meant that condition of the chambers where there has been, by some means or other, a scarcity of nitrous compounds for a short time, and where, as it were, a block of the gases pass through the whole series of the chambers, pale in colour, and with much of the SO, unconverted. As the potting of the nitrate of soda is always more or less irregular even at best, this "going through" is in a lesser degree continually taking place, and the gases must therefore show great irregularity from this cause alone. The reasoning based on such figures as I have quoted—as to the best form of chamber for the manufacture of sulphuric acid-could not be other than fallacious, and I trust to show that it is not only so, but completely at variance with the actual facts of the case. That the matter may be more clearly put before you, we will assume that we are considering the case of a series of sulphuric acid chambers, six in number; that pyrites is used as the source of the sulphurous acid, and that the gases are led first through a Glover tower (or denitrator), then into No. 1 chamber, from which they pass into Nos. 2, 3, 4, 5, and 6 in turn, passing finally through a Gay-Lussac tower (or absorber), for the recovery of the nitrous compounds, which, it is well known, before the introduction of this apparatus, were all lost by escaping into the atmosphere. We will also assume that, in such a case as we are considering, the nitrous compounds present are equal to 10 per cent. of NaNO, on the sulphur burned, are calculated as N2O, and are supposed to be altogether obtained from the Gay-Lussac acid denitrated in the Glover tower, while the residual gases escape with 10.4 per cent. of oxygen, 33 grains per cubic foot nitrous compounds calculated as NaNO3, and 5 per cent. of the original sulphur escaping as SO,; also that the gases are calculated as litres of gas per 100 grams sulphur. The watery vapour present is omitted in the calculation, as it is most difficult to decide on the bulk it occupies in the chambers, and it may quite well for our purpose be neglected forthe present, as may also the absorption of nitrous compounds by the acid formed, or their reduction to lower oxides, or even to nitrogen. To make more distinct the work done in each chamber, I have tabulated side by side the gases entering, and those leaving, each chamber, so that the alteration in their composition can be seen at a glance. As the gases enter the Glover tower they contain 6.325 vol. per cent. of SO, which becomes at the entrance to the first chamber a fraction less owing to the addition of the N2O4 to the volume of the total gases. This figure is taken for convenience of calculation. The amount of oxygen in escaping gases varies much in different cases. With tight chambers and good working it may be kept steadily about 7 per cent. to 7.5 per cent., but as chambers get old and leaky it often mounts to 10 per cent. or 11 per cent., this amount being found in the exit gases after passing all condensing towers, &c. |