The raw material having been reduced to the requisite state, it may be distilled by one of two methods or a combination of them, viz (1) Distillation by boiling with water.

(2) Distillation by means of "live" steam generated in a separate vessel or boiler.

The first is the more simple method if fire-heating be used, and is therefore largely adopted by itinerant distillers who take their stills to the fields and forests in search of their raw material. This method has some advantages over the method of distilling with steam, the apparatus is more portable and less costly, and the labour required to run it is less skilled, but it is open to the serious objection that there is danger of overheating the still in parts not in actual contact with the water; any raw material touching such a hot part is destructively distilled and gives rise to bodies having objectionable odours. The yield of oil obtained by this method is not usually so good as that obtained by means of live steam, the highest boiling fractions - which are sometimes the most valuable - tending to remain behind.

Experiments by Schimmel with lavender illustrate this point: -

It is possible also that the much slower water distillation tends to cause hydrolysis of the ester due to the prolonged heating with water, but the experiments do not definitely show this.

Distillation with Water

Typical French Itinerant Distillery

Fig. 1901 shows a typical itinerant distillery of South France. The distillation is being carried out by boiling the lavender with water, heat being supplied by means of a wood fire.

1 Kindly lent by Messrs. Roure Bertrand Fils, Grasse.

The ready mobility of these stills is noticeable, and the chief difficulty that has to be overcome is that of finding a sufficient supply of cooling water for the condensers.

Permanent Spanish Field Installation

For this reason it is not unusual to erect the still, more or less permanently, at a point where water is available and to transport the raw material over the comparatively short distances involved. This allows a somewhat more "scientific" arrangement to be adopted although at a loss of portability. This is well illustrated in Fig. 191,1 which shows an installation used in Spain for the distillation of spike lavender, thyme, rosemary, sage, marjoram, etc.

Fig. 190. - Distillation of lavender in the environs of Castellane. Roure Bertrand Fils.

This still is of considerable interest. It is built in the earth on the hill-side, a flue and chimney being arranged in the soil; the cooling water runs on to the dome-shaped top and effects a partial condensation ; it then collects in the gutter and runs through the small pipe to the coil condenser, the vapour and condensed vapour passing through the larger pipe to the interior of the coil, finally being collected in the liquid state at the bottom of the condenser. The supernatant oil layer is then separated automatically from the condensed water by means of the well-known "Florentine flask."

The dome condenser has the advantage that a large quantity of heat can be dissipated by the aerial evaporation of the thin film of water flowing over it, but the subsequent utilisation in the coil condenser of the hot water resulting from this preliminary cooling is of doubtful economy. The reverse sequence would be preferable, but involves mechanical difficulties. The most logical method is to apply the coldest cooling water to the coldest distillate and the hottest cooling water to the vapour on the counter current principle.

1 Kindly lent by Mr. Felix Gutkind, Malaga.

Fig. 191. - Felix Gutkind, Malaga.

Bulgarian Distillery For Roses

The native stills of Bulgaria are of a more permanent character, this being possible since the roses, for which these stills are used, are cultivated year after year in the same fields.

The accompanying photograph (Fig. 192) 1 of an installation in the Balkan mountains shows the stills employed. These are quite small, being of about 25 gallons capacity, and are constructed of copper tinned on the inside ; partial condensation is effected by means of the large air-cooled still-head and is afterwards completed in the usual "worm " condenser, which can be seen in the second photograph (Fig. 193), showing the method of collecting the distillate. No separating device is employed, as little or no free oil is obtained in the first distillation ; the reason for this will be explained later. It will also be noted that the incoming cooling water is supplied to the top of the condenser, and there mixing with the hot water loses much of its effectiveness in consequence.

1 Messrs. Shipkoff & Co., Rahmanlari.

American Still For Oil Of Wintergreen

Stills very similar to these are in use at Unionville, Pennsylvania, for the distillation of oil of wintergreen.1 The body of the still is surrounded by a roughly built shelter of stones, and is usually capable of holding 200 to 500 pounds of leaves; the condenser is the usual coil immersed in a barrel of running water.

Fig. 192. - Shipkoff & Co., Rahmanlari.