The water in K is heated until the contents of B are in brisk ebullition; the vapor rises through RH, is condensed on entering E and falls in small drops on the material. This fine rain of the solvent dissolves the aromatic substances and flows back into B, where it is again evaporated, and so on.
At the end of the extraction the faucets H and H1 are closed and H2, is opened. The vapors of the solvent pass through it into a worm where they are condensed; the essential oil remaining in B is drained off by opening H3.
For still larger operations more perfect apparatuses are employed, such as those of Seiffert and Vohl. Seiffert’s apparatus (Fig. 24) consists of a battery of jacketed cylinders; steam circulates in the space between the cylinders and the jackets. Each cylinder contains a plate covered with a wire net on which the flowers to be extracted are placed. All the cylinders having been filled and closed, the solvent is admitted from a container above, through S and a into C2; when this is filled the liquid flows through a2b3cn into C. The solution saturated with essential oil leaves the apparatus through dn and p and enters a reservoir. The course of the liquid is aided by the suction of an air-pump acting on p.
When the reservoir contains an amount of fluid equal to that in Cn, dn is closed, an is opened, and C connected with C1 through bn and c1. That the contents of C2 are completely extracted is shown by the fact that the liquid appears colorless in the glass tube inserted in b2; a1 and C2 are closed; a2 and C3 are opened, thereby excluding C2 from the current of bisulphide of carbon which then flows through C3CnC1. In order to permit the free flow of the bisulphide of carbon through S despite the exclusion of C2, the faucets a1a2a3an must be two-way cocks; in one position they connect S with b; in the other they close b and leave the passage through S open.
Fig. 24.
In order to collect the bisulphide of carbon present in the extracted residue in C2, faucet g2 is opened and the bisulphide of carbon allowed to escape through h. The faucet e2 in tube L on being opened admits compressed air to C2, thus hastening the outflow. If nothing escapes below, faucets f2 and fx are opened, steam enters through tube D between jacket and cylinder; the bisulphide of carbon vapor passes through g2 and h into the worm. After the expulsion of the bisulphide of carbon, C3 is emptied, refilled, connected with C1, and bisulphide of carbon admitted from C3 in the manner above described.
Fig. 25.
An extraction apparatus which has been much recommended of late is the so-called “Excelsior Apparatus” made by Wegelin and Huebner, Halle a. S., which can be worked with any desired solvent. The construction of the apparatus (Figs. 25 and 26) is as follows.