PYROLIGNEOUS ACID 



679 



showed that 0'65 oz. of silver and 3 grs. of gold had been extracted from each ton of 

 ore worked ; leaving a profit of nearly 3s. per ton on the operation, after paying all 

 expenses, including loss of iodide, &c. J. A. P. 



PYRITES, COBALT. See COBALT. 



PYRITES, COPPER. See COFFER. 



PYRITES, MAGNETIC. See PYRITES. 



PYROACETIC SPIRIT. See ACETIC ACID. 



PYROGAXiIiIC ACID. If gallic acid is carefully heated to about 400, it is 

 totally decomposed into carbonic acid and pyrogallic acid, which sublimes in brilliant 

 white plates ; it is easily soluble in ether, alcohol, and water ; it reacts feebly acid, it 

 fuses at 240, and sublimes at 400. If a solution containing peroxide of iron bo 

 added to a solution of pyrogallic acid, a black colour is struck, but the iron is rapidly 

 reduced to a state of protoxide, and the liquor assumes a rich red tint. Kane. 



Dr. Stenhouse has fully investigated the formation of gallic and of pyrogallic acid ; 

 to his papers on this subject those interested are referred. Pyrogallic acid has of late 

 years been largely employed in PHOTOGRAPHY, which see. It has also been used to 

 dye the hair a light brown. See GALL NUTS. 



PYROLIGNEOTTS ACID. See ACETIC AdD. 



The apparatus represented in figs. 1696 and 1697 is a convenient modification of 

 that exhibited under acetic acid, for producing pyroligneous acid. Fig. 1696 shows 



the furnace in a horizontal section drawn through the middle of the flue which leads 

 to the chimney. Fig. 1697 is a vertical section taken in the dotted line x, x, of fig. 

 1696. The chest a is constructed with cast-iron plates bolted together, and has a 

 capacity of 100 cubic feet. The wood is introduced into it through the opening b, in 

 the cover, for which purpose it is cleft into billets of moderate length. The chest is 

 heated from the subjacent grate c, upon which the fuel is laid, through the fire-door, d. 

 The flame ascends spirally through the flues e c, round the chest, which terminate in 

 the chimney, /. An iron pipe, g, conveys the vapours and gaseous products from the 

 iron chest to the condenser. This consists of a series of pipes laid zigzag over each 

 other, which rests upon a framework of wood. The condensing tubes are enclosed in 

 larger pipes, i i; a stream of cold water being caused to circulate in the interstitial 

 spaces between them. The water passes down from a trough Jc, through a conducting 

 tube I, enters the lowest cylindrical case at in, flows thence along the series of jackets 

 i, i, i, being transmitted from the one row to the next above it, by the junction-tubes 

 o, o, o, till at p it runs off in a boiling-hot state. The vapours proceeding downwards 

 in an opposite direction to the cooling stream of water, get condensed into the liquid 

 state, and pass off at q, through a discharge-pipe, into the first close receiver r, while 

 the combustible gases flow off through the tube s, which is provided with a stopcock 

 to regulate the magnitude of their flame under the chest. As soon as the distillation 



