l(j Dr. Ure on Clitoride oj Lime. 



nearly spherical, are in some cases made entirely of lead, in 

 others, of two hemispheres joined together in the middle, the 

 upper hemisphere being lead, the under one cast-iron. The 

 first kind of alembic is enclosed for two-thirds from its bottom 

 in a leaden or iron case, the interval of two inches between the 

 two being destined to receive steam from an adjoining boiler. 

 Those which consist below of cast-iron, have their bottom di- 

 rectly exposed to a very gentle fire ; round the outer edge of 

 the iron hemisphere a groove is cast, into which the under edge 

 of the leaden hemisphere sits, the joint being rendered air-tight 

 by Roman or patent cement *. In this leaden dome there are 

 four apertures, each secured by a water-lute. The first opening 

 is about ten or twelve inches square, and is shut with a leaden 

 valve, with incurvated edges, that sit in the water-channel at 

 the margin of the hole. It is destined for the admission of a 

 workman to rectify any derangement in the apparatus of rota- 

 tion, or to detach hard concretions of salt from the bottom. 

 The second aperture is in the centre of the top. Here a tube of 

 lead is fixed, which descends nearly to the bottom, and down 

 through which the vertical axis passes, to whose lower end the 

 cross bars of iron, or of wood, sheathed with lead, are attached, 

 by whose revolution the materials receive the proper agitation 

 for mixing the dense manganese with the sulphuric acid and 

 salt. The motion is communicated either by the hand of a 

 workman applied from time to time to a winch at top, or it is 

 given by connecting the axis with wheel work, impelled by a 

 stream of water, or a steam-engine. The third opening admits 

 the syphon-formed funnel, through which the sulphuric acid is 

 introduced ; and the fourth is the orifice of the eduction-pipe. 



Manufacturers differ much from each other in the proportion 

 of their materials for generating chlorine. In general, 10 cwt. 

 of salt are mixed with from 10 to 14 cwt. of manganese, to 

 which mixture, after its introduction into the alembic, from 12 



* A niixtuie of lime, clay, and oxide of iron, separately calciuedi and 

 reduced to a fine powder. It must be kept in close vessels, and mixed with 

 t)ie requisite water when used. 



