PYROLIGNEOUS ACID has been no ticed ander acetic acid. It is made by the distillation of wood in close vessels. The retorts are of cast iron, 6 feet long, and 3 feet 8 inches in diameter. Two of these cylinders are heated by one fire, the flame of which plays round their sides and upper surface ; but the bottom is shielded by fire-tiles from the direct ac tion of the fire. Two cwts. of coals are sufficient to complete the distillation of ono charge of wood ; 36 imperial gallons of crude vinegar, of specific gravity 1.025, being obtained from each retort. The process occupies 24 hours. The retort mouth is then removed, and the ignited charcoal is raked out for extinction into an iron chest, having a groove round its i edges, into which a lid is fitted.
When this pyroligneons acid is satu rated with quicklime, and distilled, it yields one per cent. of pyroxilie spirit (sometimes called naphtha) ; which is rectified by two or three 'successive dis tillations with quicklime.
The tarry deposit of the crude pyrolig neous acid, being subjected to dIstilla tion by itself, affords a crude pyro-acetic ether, which may also be purified by re distillation with quicklime, and subse quent agitation with water.
The pyrolignite of lime is made by boiling the pyroligneous acid in a large copper, which has a sloping spout at its lip, by which the tarry scum freely flows over, as it froths up with the heat. The fluideompound thus purified is syphoned off into another copper, and mixed with a quantity of alum equivalent to its strength, in order to form the red liquor, or acetate of alumina, of the calico-prin ter. The acetate of lime, and sulphate of alumina and potash, mutually decompose each other ; with the formation of sul phate of lime, which falls immediately to the bottom.
M. Kestner, of Thann, in Alsace, ob tains, in his manufactory of pyroligneous acid, 5 hectolitres (112 gallons imperial, nearly) from a cord containing 93 c.ubie feet of wood. The acid is very brown, much loaded with tar, and marks 5° Baume ; 220 kilogrammes of charcoal are left in the cylinders ; 500 litres of that brown acid produce, after several distil lations, 375 of the pyroligneous acid of commerce, containing 7 per cent. of acid,
with a residuum of 40 kilogrammes of pitch. For the purpose of making a crude acetate of lead (pyrolignite) lie dries pyrolignite of lime upon iron plates, mixes it with the equivalent decomposing quantity of sulphuric acid, previously di luted with its own weight of water, and cooled ; and transfers the mixture as quickly as possible into a east-iron cylin dric still, built horizontally in a furnace ; the under half of the mouth of the cylin der being always cast with a semicircle of iron. Tie acetic acid is received into large salt-glazed stone bottles. From 100 parts of acetate of lime, he obtains 133 of acetic acid, at 38° Baume. It con tains always a little sulphurous acid from the reaction of the tar and the sulphuric acid.
Stoltze has ascertained, by numerous experiments, that one pound of wood yields from 6 to 74 ounces of liquid pro clucts; but in acetic acid it affords a quantity varying from 2 to 5, according to the nature of the wood. Hard timber, which has grown slowly upon a dry soil, gives the strongest vinegar. White birch and red beech afford per pound 74 ounces of wood vinegar, 14 ounce of combustible oil, and 4 ounces of charcoal. One ounce of that vinegar saturates 110 grains of carbonate of potassa. Red pine yields per pound 64 ounces of vinegar, 24 ounces of oil, 31 ounces of charcoal ; but one ounce of the vinegar saturates only 44 grains of carbonate of potassa, and has therefore only two-fifths of the strength of the vinegar from the birch. An ounce of the vinegar from the white beech, hol ly oak (Ilex), common ash, and horse chestnut, saturates from 90 to 100 grains of the carbonate. In the same circum stances, an ounce of the vinegar of the alder and white pine saturates from 58 to 60 grains.