1868 The complete Practical Distiller

173

SPECIAL DISTILLATIONS.

it wouid, at least, be attenuated in many instances. The difficulty which is attached to the distillation of lees-wines is the solid substances which they retain in a state of suspension. These substances, which are denser than the wine, pre- cipitate themselves to the bottom of the vessels in which they are deposited ; and if these vessels are stills exposed to the direct action of the fire, they cause them to stick and adhere strongly to the bottom, where they burn and give birth to all the products of the combustion of organ- ical bodies, among which the empyreumatic oil is in large quantities. The influence of this oil on spirituou3 liquors is too well known. Several means have been imagined to pre- vent this accident. Experience has taught, for instance, that when lees-wines has gained the temperature of ebul- lition, and when vapour is formed in a continuous manner on the bottom of the still, its rising, occasioned by the ascensive agitation, is an obstacle to the precipitation of solid matters, and of course to their torrefaction. . This phenomenon is easily conceived, and it is pre- sumed it is not in want of being further developed. In consequence of this observation, a vertical bar has been established in the centre of the still, and by these means a chain has been made to sweep the bottom of it. However, it has been ascertained that this precaution is not always efficacious, and that during the distillation the workman might happen to be neglectful in alimenting the furnace, so as to maintain the still in a complete movement of ebullition ; the solid matter, not being any longer suspended, precipitates itself to the bottom of the 15"^