1835.] Purification of Pyroligneous Acid, Sec. 137 



from the hearth, by a partition of bricks 3 or 4 inches high ; 

 12 inches above the outlet of the earth there is a layer of 

 iron bars IJ to 2 feet from each other, and upon these is 

 deposited the drying plate. This consists of cast-iron \ of 

 an inch thick, and is formed according to the size of the 

 furnace. Round the plate the furnace is built up to the 

 height of 10 inches, on the side of the front wall, leaving 

 room for doors, which may be calculated at 2J feet. These 

 doors are two, one above the other, through which the whole 

 interior of the furnace can be inspected. They are formed 

 of plate-iron, and have in their middle a sliding door to 

 admit of the exit of the vapour from the acetate of lime 

 and of some ventilation. A wall built at the end of the 

 plate or a clay partition separates the whole of the drying 

 plate from the chimney. In the walls of the furnace, 

 iron-bars are fixed, and upon these lies a second drying 

 plate which covers the drying space. This plate as it does 

 not come in contact with the fire may consist of good 

 iron or of clay. 



Above this drying space another is formed by means 

 of the chimney. The heat passes as well under as above 

 the drying space, and passes into the chimney, which is 

 situated at the side of the furnace, and can be shut by a 

 valve. In the drying space the temperature is usually be- 

 tween 60° and 90° R. (167° to 234^° F.) 



Turf forms the best material for fuel as it does not burn 

 rapidly, and produces a steady and equal temperature. 



Drying of the Acetate of Lime. — When the furnace is 

 thoroughly and equally heated, the flame of the fire is 

 allowed to subside. If wood is employed as fuel, the sliding 

 door should be opened at the commencement, in order to 

 allow the moisture to escape. The salt is transferred from 

 the evaporating vessel to the drying plate, and spread out 

 to the depth of two inches ; and, after the first portion has 

 become somewhat dry, the depth is increased to four or five 

 inches ; the heat is preserved at the degree already men- 

 tioned for twenty-four hours, and during this time the salt 

 is turned several times. Subsequently, when the mass 

 appears to be becoming dry, the temperature may be in- 

 creased to 100° (257- F.) so as to dry it completely. The 

 mass is dry and properly roasted when it possesses the 



