It is not possible, however, by this apparatus to ke ep the sulphur regularly supplied, and also the brimstone easily becomes sticky from overhenting,, and does not then flow well: These are decided defects. The only modified form of brimstone burner which has•been reeeived with favour by manufacturers is Harrison Males furnace. This furnace consists of two distinct compartments, in one of which the sulphur is partly burnt, partly sublimed, while in the other the combustion is completed by a further addition of atmospheric air. In spite of the great In at generated in the fu usco the. sublimation caused by it is infinitesimal, and this heat offers a decided advantage in that it enables the Glover tower to be used, which is impossible with any other foi in of blinistoue kiln. We shall presently shorn the great gain effected by the use of the Glover tower.
fn Harrison Blair's furnace, the furnace bed is slightly dished, rend slopes to within 2 ft. of the door, where a raised phittb•in is made, on which the residue, scraped off the floor once every twenty four hours, may lie exposed to the heat until the next day's residue is drawn up in a similar manner. The door is a loose iron plate in an iron frame, slightly inclined to make a tight joint, and easily removable.; in it ore drilled a number of holes for the admission of air, which can he diem] at wil 1 by a sheet-iron slide. The brimstone is introduced through a hopper, from which an iron pipe 7 in. in diameter descends to within 6 in, of the floor of the furnace, and is protected by another pipe of larger diameter. A fire-clay damper regulates the passage of the gases from the first port of the kiln to the second part, and by opening or closing this damper a larger or smaller quantity of brimstone may be burn«1 in a given time—within certain limits, of course.
Tho sulphurous ncid and sulphur vapours passing to the combustion oven, are met by a current of air, admitted through an aperture, which is provided with a damper S in. by 3 in. for regulating the admission of the exact quantity necessary for the perfect combustion. This is ascertained by taking out the smell stopper ; the admitted air should produce no flame. Thereof of the combustion oven is of fire lumps supported on dwarf walls, and forming at the same time the floor of the nitre oven. The genes rise into the nitre oven and pass over the nitre pots. These nitre pots are renewed every two hours in alternate sets, each set remaining six hours in the oven. Iron doors corresponding with each compartment provide for their removal. The gases now mixed with those arising from the decomposition of the nitre, pass under a cast-iron dome, for the purpose of living deprived of n portion of their heat, and thence by a east-iron chimney 24 ft. in height, to a small
cooling clmber, 6 ft. wide, 18 in. high, and 18 ft. long, the roof and floor of which are covered with water, which communicates with the sulphuric acid chamber. These two last-named portions of the kiln, as well as the cooling chamber, may be dispensed with, without in any way interfering with the working of the kilu, and in fact when used in conjunction with a Glover tower, the gases are taken direct from the combustion oven into the tower.
In a furnace of the dimensions 2 ft. by 4t ft., 26 tons of brimstone have, it is said, been satisfactorily burnt in a week, and the same furnace may be made to consume only 5 or 6 tons weekly by admitting less air to feed the combustion. It is also said to have been found thnt a much larger quantity of brimstone may be safely burnt in the same chamber-space than is the ease with ordinary burners.
When the necessary nitric acid gas is not derived from the decomposition of nitre with sulphuric acid in the sulphur kilns in a gaseous form, but is instead introduced into the chambers as a liquid, much more plant is necessary.
Ready-made nitric acid cannot well be admitted to the chambers otherwise than iu a tiny stream, and it is imperative that the flow shall be kept absolutely constant and regular, so that the acid may be utilized as constantly as it is required. This object is most easily achieved by a Marriotte vessel, which gives a perfectly regular outflow, and is in use in most works. Fig. 42 shows such a vessel. The stoneware vessel A, which holds the nitric acid, is closed by a perforated indiarubber cork a, in which the glass tube b is fastened, so that no air can pass through the joint. This pipe forms the only way by which air can be brought into the vessel A to fill up the space left by the acid flowing out at the tap e. The pressure of the atmosphere above the line hh', to which the glass tube reaches, regulates the outflow, and this pressure remains constant so long as the acid does not sink below that level. In order to observe the rate of flow, re course is had to the glass register d, which is tightly screwed on to the vessel, and may be read off by the adjacent scale e. The filling of the vessel is effected through the open glass tube b, which is furnished with a funnel at the top for this purpose. It is necessary first to draw out the cork a somewhat, in order to admit of the escape of the displaced air ; this may be avoided, however, if a second smaller tube be inserted into the cork, which may be closed by a pinch-cock, and only opened when the vessel is about to be filled. The escaping acid flows through glass or stoneware tubes, whose commencement is seen at f, into one of the leaden chambers.