CHEMISTRY. 27 
of the operation. This removal of water is effected by means of the 
following forms of drying apparatus: 
The Drying Apparatus with Sulphuric Acid. Pl. 31, fig. 15. 
This consists of the receiver A, fitting air-tight on a plate like that of the 
air-pump, and of the capsule, B, placed beneath the receiver, and half filled 
with concentrated sulphuric acid. The object of the acid is to remove 
moisture from the inclosed air by reason of its great affinity for it. The 
substance to be dried is placed finely powdered in a porcelain capsule, upon 
a triangle of iron wire (fig. 12) resting on the dish containing the acid, and 
is then to be left for several days. The moisture of the body gradually 
exhales in the perfectly dry air, and the capsule loses in weight by the 
amount of the water exhaled and absorbed by the sulphuric acid. Fig. 17 
shows a still more advantageous construction of this apparatus. B is a 
large glass vessel with a ground edge; D, the contained dish with the 
sulphuric acid; C, a wire frame upon which the capsule with the object to 
be dried is set; A is a ground-metal cover, closing air-tight on the edge of 
B, previously rubbed with tallow. In its centre is an aperture, likewise 
capable of being closed by a ground-cover, and through which small objects 
may be introduced into the apparatus. For such substances, however, 
as sugar, which are capable of experiencing a pretty high heat 
without decomposition, other apparatus of quicker operation may be 
employed. Such are the water-bath, the oil-bath, and the air-bath 
(pl. 31, figs. 16,18, 19, 20, 21). First, the water-bath (fig. 16). A isa 
copper vessel, with a properly fitting cover, possessing two intersections to 
receive the two legs of the glass vessel (fig. 20) set in A, and containing 
the substance to be dried. To one leg is connected the chloride of calcium 
tube c, which is continued into a tube bent at right angles; to the other 
leg is likewise attached the chloride of calcium tube b. The former is 
fitted air-tight by means of cement in the cork of one opening of the Wolff 
apparatus B. The second opening, e, of the bottle contains a funnel tube, 
and in the third, f, is fixed a syphon. The kettle, A, is to be filled with 
water, so that the vessel (fig. 20) containing the substance to be dried may 
be completely covered, and the water brought to boil by means of the 
furnace C. At the same time a vessel filled with water is placed above the 
funnel-tube, e, from which water may be made continually to drop into the 
funnel. The water thus entering soon covers the bottom of the syphon 
tube, and drives the air from the bottle, B, into the chloride of calcium tube 
c, in which all the vapor contained in the air in B is retained. A stream 
of perfectly dry air then passes through the vessel containing the substance 
in question, and soon takes up all the moisture which may be there. The 
chloride of calcium tube b absorbs the water thus abstracted from the 
substance. By extracting the cork containing the funnel-tube, and starting 
a current of water from the syphon, the water in B may be removed, and 
the operation of furnishing a current of dry air again continued as before. 
457 
