MANUFACTURE OF WOOD-VINEGAR. 237 



burette. If up to the appearance of the precipitate 3.5 cubic cen- 

 timetres have been used, 3.5 cubic centimetres of the copper solu- 

 tion must be diluted to 5 cubic centimetres or 700 cubic centi- 

 metres to 1 liter. This forms the ammoniacal copper solution 

 standardized to normal nitric acid. 



To determine the strength of the wood-vinegar with this fluid, 

 dilute 10 grammes - of it with water, and add, with constant agita- 

 tion, copper solution until turbidity appears. The copper solution 

 being standardized to normal nitric acid and the latter to normal 

 sodium, the quantity of copper solution consumed is evidently just 

 as large as the quantity of normal sodium would have been if 

 used for titration. 



Working up the Wood- Vinegar. 



Only a small quantity of wood-vinegar is used for antiseptic 

 purposes and in medicine, the greater portion being manufactured 

 into wood-spirit, acetone, and acetic acid, as well as into acetates. 



There are two methods by which this can be effected. By the 

 first the acetic acid of the wood vinegar is directly converted into 

 acetate by saturating with hydrate of lime (slaked lime) and the 

 wood-spirit distilled off. This can be effected in a cast-iron still, 

 distillation being continued as long as a fluid specifically lighter 

 than water passes over. The distillate is crude wood-spirit, and 

 the residue is the still impure calcium acetate. 



By the second method, which is in general use, the more vola- 

 tile portion (about one-tenth) of the crude wood-vinegar is dis- 

 tilled off in order to obtain wood-spirit as the distillate. 

 This has to be effected in a copper still. If the crude wood- 

 vinegar is not entirely clear, it is best for either method to first 

 pass it through a sand or charcoal filter. 



By the second method the wood-vinegar is subjected to distil- 

 lation in a copper still of about 106 cubic feet capacity, Fig. 56, 

 over a free fire, or less often by means of steam. What passes 

 over first contains, besides water, wood-spirit, methyl acetate, ace- 

 tone, and acetic acid. The vapors are, however, not allowed to 

 completely condense at once but are rectified on the way by being 

 conducted, as shown in the figure, through two or three rectifying 

 vessels arranged in the same manner as in Pistorius's alcohol 



