MANUFACTURE OF WOOD-VINEGAR. 229 



uses a cylindrical copper receptacle, d, Fig. 55, provided with a 

 false bottom, upon which is placed a layer of crystallized soda 

 from 2J to 2J feet deep. The vapors of water and acetic acid 

 dissolve the soda, and the temperature thereby being lowered, a 

 further portion of the volatile bodies, especially wood spirit, is 

 precipitated. By distilling the fluid thus obtained, the wood spirit 

 is regained, and the residue in the still used for the preparation 

 of sodium acetate. 



For a condenser for four retorts of a capacity of 4 cubic me- 

 tres (141.26 cubic feet) each, Gillot gives the following approved 

 dimensions, provided the period of distillation is 72 hours : The 

 diameter of the pipe at its entrance into the water trough is 15| 

 inches, and at its exit 5f inches ; its total length is 164 to 180 

 feet, this length being divided between 6 straight pieces and their 

 elbow-joints. The vat is 26 J feet long with a depth of 5J feet. 



The arrangements suitable for the carbonization of wood having 

 been described in the preceding pages, the most important products 

 will now be more closoly considered. Before doing this a few re- 

 marks as to the most suitable varieties of wood, and their con- 

 stitution, may be acceptable. 



Oak, beech, hornbeam, ash, and birch give the largest yield of 

 wood vinegar, less being obtained from the conifers, poplar, 

 willow, and aspen. On the other hand, the conifers as well as 

 the bark of birch yield considerable quantities of volatile oils. 



Woods about 20 years old seem to be especially suitable for the 

 purpose of distillation. The trees should be felled in the winter, 

 and the wood allowed to lie for six months and not over two years. 

 It should be protected from rain and snow. To facilitate drying, 

 it is best to free the wood from the bark, this being of special 

 importance in regard to birch, the bark of which yields about 

 40 per cent, of tar and empyreumatic oil, and the wood only 2 

 per cent., hence the removal of the bark essentially facilitates the 

 purification of the wood-vinegar. The removal of the bark is 

 best effected by the introduction of steam of about one atmospheric 

 pressure into a wooden vat covered with felt, and provided with 

 a perforated false bottom, upon which the pieces of wood rest. 

 After allowing the steam to act for about three hours, the bark can 

 be readily detached. By drying the air-dry wood in the semi- 



