STILLS.
FIG. 1.
FIG. 2.
FIG. 3.
These are vessels of different kinds used in distilling, that is, when any volatile product has to be converted into vapour and afterwards condensed, for the purpose of separating it from various matters not otherwise separable. One of the oldest forms of still is that even yet used in most chemical operations, called the “retort” ([fig. 1]). It is blown out of glass in one piece, is easily made of all sizes, not exceeding a few gallons; it is chiefly used for distilling small quantities of fluids, and those which act on metals, as the acids. For some purposes, chiefly those requiring a very high temperature, earthenware retorts are used, and in other cases retorts made of platinum; the retort is often “tubulated,” a name given to those with an orifice in the upper part having a stopper fitted to it, this opening is useful to introduce any substance while the body of the retort is already partly filled with its contents, or to add more of anything from time to time as it distils over. An indispensable adjunct to the retort is a “receiver” for condensing the liquid distilled; this is generally of a globular form, with an opening to receive the spout of the retort, which is also frequently “tubulated” that it may be attached by a bent tube to a second or third receiver. The receiver is to be kept cool, and this is generally done by a stream of cold water being poured on it, or a cloth dipped in cold water being spread over it, &c. The stills properly so called, such as are used in the manufacture of large quantities of liquids, as, for example, in the distillation of spirit, are generally made of copper tinned inside to prevent the formation of verdigris, and consist of a body, a head, and a condenser, the common form of which is seen at [fig. 2]. The condenser consists of a long tube coiled up into a spiral and placed in a large tub of water, having a supply tube to let in cold water at the bottom, and one for the exit of the hot water at the top, for hot water being lighter than cold, rises up to the top of the tub. A very good form for a small portable condenser may be seen at [fig. 3], in which a constant current of cold water is made to pass through the outer tube, and so keep the inner one cold.
FIG. 4.
FIG. 5.
A distilling apparatus for experiments in chemistry can easily be made with flasks and bent glass tubes, [fig. 4], or even by means of pieces of tube alone as in [fig. 5], one being bent and the other straight; the tubes and flasks can be united by means of corks perforated by a round or keyhole file. Empty oil-flasks serve well for this purpose, they can readily be cleansed by putting a little oil of vitriol into them, shaking it well about, and then washing them out with clean water.