Stills In Tunis And Ceylon

The small size of these stills is in great contrast to those used in other parts of the world. In Southern Tunis stills ranging up to 150 gallons capacity are employed. Two stills are generally employed with one condenser, so that one still is in operation while the other is being cleansed and recharged with fresh herbs. This convenient method is also employed in Ceylon for the distillation of lemon-grass and citronella oils. The photograph (Fig. 194) shows the arrangement in use in Tunis. The two stills have a common "swan-neck," by means of which the vapour is conducted to the condensing coil immersed in a concrete tank of water; the operation of changing the still-head from one still to the other is facilitated by means of the overhead gantry.

1 From information kindly supplied by John T. Stolz, Broadheadsville, Pa.

Crude Javanese Plant

In some instances itinerant distillations are carried out in the crudest imaginable manner with makeshift plant of the most unsuitable character. It is not unusual for the still to consist of an old locomotive boiler set on end, a pipe, running for a considerable distance along the bed of a stream, serving for the condenser. A very usual type of native still is shown in the illustration (Fig. 195), the one in particular being used in Java for distilling Cananga oil.

Fig. 193. - Shipkoff & Co., Rahmanlari.

Portable Fire-Heated French Still

Very adaptable and convenient stills are readily to be obtained in Europe ; a portable fire-heated type is depicted in Fig. 196.1

1 Still constructed by Deroy Fils Aine, Paris.

A highly interesting "portable ' steam-distilling plant is shown in Fig. 197. This plant is in use for distilling rosemary and consists of a fire-heated steam generator, which supplies steam under low pressure to the bottom of a cylinder containing the herb supported on a false bottom; two such cylinders are employed, one being recharged while the other is in use, and each being provided with a detachable head, which can be removed in order to introduce or remove the herb. These detachable heads can be connected as required to a common condenser.

Fig. 194. - Perfumery and Essential Oil Record, 1916.

Fig. 195. - Schimmel & Co., Leipzig.

Distillation with Live Steam

Distillation with "live" steam generated in a separate boiler is more suitable for the established distillery, since, in general, better results are to be obtained than with water distillation.

If "live" steam be used its pressure must not be excessive, as there exists a strong tendency deleteriously to alter the oil if it contain delicate constituents such as aldehydes or esters.

Fig. 196. - Deroy Fils Aln6, Paris.

The following experiment1 demonstrates the hydrolysing action of "50 lb. steam " on lavender oils: -

In general a boiler-steam pressure of as little as 2 lb. per square inch is sufficient, but if it is necessary to use a higher pressure the hydrolysing effect can be mitigated by coiling the steam inlet pipe round the inside on the bottom of the still after the manner of a volute or "watch spring" spiral, and ensuring that sufficient free water to cover the spiral be in the still.

The danger of destructively distilling the raw material is avoided with steam distillation, and is not likely to arise if a closed steam coil or a steam jacket is employed for boiling the water in the still, since the highest local temperature possible is that of the steam itself.

1 A. Boake Roberts & Co., Ltd., London.

The best distillery practice is to fit the stills for both water and steam distillation, steam being used as the heating medium in both cases.

Material For Still

Copper is the most usual material of which these stills are constructed, but it is not necessary to employ such expensive material; iron is generally quite as satisfactory, and aluminium is now being used to a large extent; even wooden vats can be successfully employed, and are in regular use in Australia for the production of eucalyptus oil, and in America and England for peppermint. Some of these vats are capable of holding two tons of material.

It is customary in America to coat the inside of wooden stills with a waterproofing compound, which not only protects the wood, but eliminates, to a large extent, the danger of contaminating one oil with another if the still is used for more than one preparation. Such stills have been found to be quite suitable for distilling sassafras, cedar, spruce, etc., the heating medium being steam generated in a separate boiler. Wooden vats having copper or galvanised iron bottoms have been used successfully for distilling birch with water by direct heat; but lead linings are unsatisfactory, since the lead tends rapidly to become distorted.