ABSORBER TABLE.
The purifying apparatus for the air-current is compactly and conveniently placed on a solidly constructed table which can be moved about the laboratory at will. The special form of caster on the bottom of the posts of the table permits its movement about the laboratory at will and by screwing down the hand screws the table can be firmly fixed to the floor.
The details of the table are shown in fig. 30. (See also fig. 4, page 4.) The air coming from the calorimeter passes in the direction of the downward arrow through a 3/4-inch pipe into the blower, which is immersed in oil in an iron box F. The blower is driven by an electric motor fastened to a small shelf at the left of the table. The air leaving the blower ascends in the direction of the arrow to the valve system H, where it can be directed into one of the two parallel sets of purifiers; after it passes through these purifiers (sulphuric-acid vessel 2, potash-lime container K, and sulphuric-acid vessel 1) it goes through the sodium-bicarbonate can G to a duplicate valve system on top of the table. From there it passes through a pipe along the top of the table and rises in the vertical pipe to the hose connection which is coupled with the calorimeter chamber.
The electric motor is provided with a snap-switch on one of the posts of the table and a regulating rheostat which permits variations in the speed of the motor and consequently in the ventilation produced by the blower. The blower is well oiled, and as oil is gradually carried in with the air, a small pet-cock at the bottom of the T following the blower allows any accumulated oil to be drawn away from time to time. The air entering the valve system at H enters through a cross, two arms of which connect with two "white star" valves. The upper part of the cross is connected to a small rubber tubing and to the mercury manometer D, which also serves as a valve for passing a given amount of air through a series of U-tubes for analysis of the air from time to time. It is assumed that the air drawn at the point H is of substantially the same composition as that inside the chamber, an assumption that may not be strictly true, but doubtless the sample thus obtained is constantly proportional to the average composition, which fluctuates but slowly. Ordinarily the piping leading from the left-hand arm of the tube D is left open to the air and consequently the difference in the level of the mercury in the two arms of D indicates the pressure on the system. This is ordinarily not far from 40 to 50 millimeters of mercury.
Fig. 30.—Diagram of absorber table. 1 and 2 contain sulphuric acid; K contains potash-lime; G, sodium bicarbonate can; F, rotary blower for maintaining air-current; H, valves for closing either side; and D, mercury manometer and valve for diverting air to U-tubes on table. Air leaves A, passes through the meter, and then through drying tower B and through C to ingoing air-pipe. At the left is the regulating rheostat and motor and snap-switch. General direction of ventilation is indicated by arrows.
The absorber table, with the U-tubes and meter for residual analyses, is shown in the foreground in fig. 2. The two white porcelain vessels with a silver-plated can between them are on the middle shelf. The sodium bicarbonate can, for removing traces of acid fumes, is connected in an upright position, while the motor, the controlling rheostat, and the blower are supported by the legs near the floor. The two rubber pipes leading from the table can be used to connect the apparatus either with the bed or chair calorimeter. In fig. 4 the apparatus is shown connected with the bed calorimeter, but just above the lowest point of the rubber tubing can be seen in the rear the coupling for one of the pipes leading from the chair calorimeter. The other is immediately below and to the left of it.