On extrading Vinegar from IFood. 44 1 



and forty to three hundred Htres of pyroligneous acid, containing 

 one-twelfth of tar. 



The charcoal retains the form of the wood ; it is intermixed 

 only with a small quantity of dust which proceeds from the bark ; 

 it possesses all the qualities of good charcoal, but its combustion 

 is more rapid and more brilliant, and less is required for raising 

 liquors to i)oiling heat. If exposed in contact with the air, it 

 gains ten per cent, in weight. 



The most satisfactory results are obtained from hard woods ; 

 but white woods are rejected : it takes five or six hours to char 

 the wood, and seven hours to cool the charcoal. 



When the retort is taken out, the pyroligneous acid is a red- 

 dish, semi-transparent liquid, and of a strong empyreumatic acid 

 taste and smell ; every hundred parts will saturate as much sub- 

 carbonate of alkali as seven and a half to nine and a half of sul- 

 phuric acid will concentrate. 



The liquid flows from the condenser in a continual stream, of 

 the size of a goose quill, and is conducted into a large wooden cask 

 placed in a cellar, where, in cooling, it deposits the greater part 

 of its tar ; hence it passes into another cask, where it remains 

 in store. 



It is preferable in this state to vinegar for all kinds of dyeing 

 and printing on linen ; it possesses an oil which is an excellen: 

 mordant for linen and cotton, and prints with a more brilliant, 

 durable, and fine colour. It likewise serves to give a rose-colour 

 to woods, feathers, and straw, &c. 



In order to separate the acid from the empyreumatic oil, whic't 

 colours and changes its nature, it is run into a large iron boiler, 

 where as much subcarbonate of lime is added as it can de- 

 compose when cold. When arrived at this point, a certain 

 quantity of the tar which floats on the surface is taken off with 

 a skimmer, and by means of a pump the liquor is raised up in a 

 cauldron, where it is then boiled. The saturation is then con- 

 tinued with quick-lime, and decomposes the acetate of alkali 

 which remains in dissolution; and the sulphate of lime which 

 precipitates, carries with it a fresh quantity of tar. 



The deposit being accomplished, the liquor is passed into 

 another cauldron, and there it is concentrated by a slight boilin:; 

 till a thin skin arises; then it is put into wooden tubs, where in 

 cooling it becomes solid. 



The produce thus obtained is extremely impure and black, in 

 consetiuence of its retaining some portion of oily matter. This 

 foreign .substance resists repeated crystallization, and cannot bf 

 taken away except by melting. These impure crystals are there- 

 fore put into a cabt-iron cauldron, where they undergo the 



aqiieous 



