10 OPERATIONS AND INSTRUMENTS 



sometimes done. Glass retorts are generally 

 placed in a sand-bath, or suspended over a lamp, 

 for which ARGAND'S lamp is the best. The re- 

 ceiver is placed upon some stand convenient for 

 the purpose, with a ring made of hay under it, or 

 some such contrivance, to keep it steady. 



A (Fig. 2.), is a vessel called a mattrass, for the 

 same purpose, having a vessel, B, called an alembic, 

 fitted to the head. The liquid raised by heat into 

 the state of vapour, is condensed in the alembic, 

 and falls into a groove all round its inside, from 

 whence it runs out by the spout, C, into the re- 

 ceiver, D. 



Fig. 3. are conical tubes that fit into another, 

 for lengthening the necks of retorts, &c. to con- 

 nect them with the receivers at any distance: they 

 are called adopters. 



Fig. 4. are phials with bent glass tubes fitted in 

 them, for disengaging gases, and similar experi- 

 ments : they were used by PRIESTLEY, and are 

 hence called Priestley's bottles, and sometimes 

 proofs : they are either tubulated or plain. 



A (Fig. .5.), represents a common still. It is a 

 large vessel of copper, into which the materials 

 to be distilled are put. The still is built up in 

 brick- work, which covers it up to the neck; the 

 fire is applied underneath, and runs round it in a 

 spiral manner. B is the head of the still. This 

 head is connected with the worm, which is a spiral 

 tube, immersed in a vessel of cold water, called the 

 refrigeratory, or cooling tube, C. The liquor be- 

 ing condensed in its passage through the worm, 

 runs out at the cock, D, into the vessel placed 

 there to receive it. 



This is $e construction of the common still for 

 distilling spirituous liquors ; but a very great im- 



