A filter of simple construction, and performing excellent service, is shown in Fig. 1. It consists of a large glass bottle, _F_, hermetically closed by a doubly-perforated cork. The neck of the glass funnel _T_, the upper rim of which is ground smooth, is placed in one of the holes, and a glass tube, _r_, bent at a right angle, is fitted into the second hole. A thick wooden lid, with a rubber ring on the lower side, is placed upon the funnel, thus closing it air-tight. In the centre of the lid is fitted a glass tube, _r´_, also bent at a right angle, which is connected with the tube _r_, by a rubber hose, _k_. After the funnel has been provided with filtering paper and the oil to be filtered, the lid is placed upon it, and must not be removed, except for the purpose of pouring more oil into the funnel. The air in the bottle _F_ is displaced by the oil dropping into it, and escapes through _r_, _k_ and _r´_ into the funnel, and thus only the air in the bottle and funnel can act upon the oil. The other method for the complete purification of expressed oil is by rectification or distillation with water. For this purpose the oil, together with a little water, is brought into one of the stills described later on, and the oil distilled over. It is sometimes difficult to obtain the last portion of the oil, especially with a still heated by direct fire, and it is therefore preferable to combine it with a fresh quantity of the same oil to be distilled. _Distillation._--There are at present two methods in use. The one is founded upon the direct action of the heat, the other upon the use of steam. The first was formerly in general practice, and is still largely employed in France and England, and to a limited extent in this country. It is, however, very deficient in many respects. As the stills must necessarily be of small capacity, only small quantities can be distilled at one time, and the oils very rarely possess the peculiar odor due to them, and sometimes the odor is even altered. In mixing too little water with the materials to be extracted, there is danger that empyreumatic oils will be formed; a large quantity of water, on the other hand, is of disadvantage, in so far as in case the perfume-materials contain little oil, only a perfumed water, but no oil, will be obtained. In order to avoid these inconveniences, or, at least, to do away with some of them, another plan was devised. The materials to be distilled were spread upon sieves, which were suspended in the upper part of a still, so that they might be penetrated from below. It is true no scorching is possible in this case, as was in the other process when the heating was continued after all the water had evaporated, and the oil retains its proper color, but by this method only small quantities can be extracted at a time. The still generally used for distillation with direct heat resembles so much an ordinary whiskey still as to need no further description here. [Illustration: FIG. 2.]