MANUFACTURE OF WOOD-VINEGAR. 243 



gases escape directly into the chimney, and the first pan is 

 emptied into the crystallizing boxes. The latter are oblong sheet- 

 iron vessels placed alongside each other and slightly inclined 

 towards one of the narrow sides. The emptied pan being filled 

 from the next, and the latter Avith fresh solution, the register is 

 re-opened and evaporation commenced anew. 



When crystallization is finished the mother-lye is drawn off 

 into a vat, and, after draining oif, the salt is freed from the still 

 adhering mother-lye by means of a centrifugal. The crystals are 

 then brought into an iron pan heated by steam and re-dissolved 

 with just sufficient water to at once yiejd a hot solution of 28 

 B., which is again brought into the crystallizing boxes. 



The crystals now obtained are larger and of a pale brown 

 color, and moist with mother-lye. After draining off they are 

 moistened with a saturated solution of pure acetate and separated 

 from the mother-lye by means of a centrifugal. The crystals 

 while in the centrifugal may be again moistened with a small 

 quantity of the pure acetate solution, and are then obtained suf- 

 ficiently pure to be at once distilled with sulphuric acid. The 

 acid thus obtained, though not entirely pure, is much better than 

 that from calcium salt. 



To obtain entirely pure sodium acetate, the pale brown salt 

 obtained from the second crystallization is calcined, or, what is 

 more simple and better, its hot solution filtered through animal 

 charcoal. The salt is dissolved in water by means of steam, so 

 that a nearly boiling solution of 15 to 16 B. is obtained, which 

 is then slowly filtered through a layer of animal charcoal the size 

 of a pea in an iron cylinder, which is covered with thick felt in 

 order to retain the heat. When the charcoal ceases to act it is 

 washed with water and the washwater used for dissolving a fresh 

 quantity of salt. The charcoal is revived by drying and glowing 

 in closed cast-iron pots and re-used. The aqueous solution of 

 the pale brown acetate, together with 10 per cent, of its weight 

 of bone-black, can also be heated for a few hours with constant 

 stirring in an iron or copper boiler, and, after settling, decanted. 

 The solution is treated with animal charcoal, and after crystal- 

 lizing and passing through the centrifugal, yields an entirely pure 

 salt, 



