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 H_{1} are closed and H_{2}, 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 H_{3}. 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 C^2; when this is filled the liquid flows through _a_^2_b_^3_c_^n into C. The solution saturated with essential oil leaves the apparatus through _d_^n 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 C^n, _d_^n is closed, _a_^n is opened, and C connected with C^1 through _b_^n and _c_^1. That the contents of C^2 are completely extracted is shown by the fact that the liquid appears colorless in the glass tube inserted in _b_^2; _a_^1 and C^2 are closed; _a_^2 and C^3 are opened, thereby excluding C^2 from the current of bisulphide of carbon which then flows through C^3C^nC^1. In order to permit the free flow of the bisulphide of carbon through S despite the exclusion of C^2, the faucets _a_^1_a_^2_a_^3_a_^n 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. [Illustration: FIG. 24.] In order to collect the bisulphide of carbon present in the extracted residue in C^2, faucet _g_^2 is opened and the bisulphide of carbon allowed to escape through _h_. The faucet _e_^2 in tube L on being opened admits compressed air to C^2, thus hastening the outflow. If nothing escapes below, faucets _f_^2 and _f_^x are opened, steam enters through tube D between jacket and cylinder; the bisulphide of carbon vapor passes through _g_^2 and _h_ into the worm. After the expulsion of the bisulphide of carbon, C^3 is emptied, refilled, connected with C^1, and bisulphide of carbon admitted from C^3 in the manner above described. 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. [Illustration: FIG. 25.] [Illustration: FIG. 26.]