442 On extracting Vinegar from IVuod. 



aqiieom fusion; all the water that ihev contain is evaporated; 

 and when they are dry, the fire is increased till all ,thc matter is 

 in a burning fusion. It is then run into appropriate squares, 

 in which it becomes solid. 



In this state it is black like coal, but it easily dissolves in warm 

 •water; and this solution filtered and stirred with care gives cry- 

 stals of acetate of alkali, which retain scarcely any of the em- 

 pyrcuma. It is then melted in a certain large (juantity of water,, 

 and is decomposed by means of sulphuric acid of commerce; it 

 then gives out sulphate of alkali crystallized, and acetic acid, 

 which only remains to be distilled to be obtained in perfect pu- 

 rity. The procGcs may be carried on in large stone pitchers, 

 called tourilles. While the burning fusion is going on, only a 

 small quantity of acetate of alkali is decomposed, which depends 

 probably on the presence of the oily matter. 



This acetic acid, thus rectified, shows eleven degrees on the 

 hydrometer of Baun)e. It is to be preferred to distilled vinegar, 

 as the latter is never so concentrated, and always retains some 

 portion of vegetable matter which injures the beauty of the 

 fabrics ; besides which, for all preparations to be done with 

 the acetic acid of wood, it does not require to be purified. 



In order to concentrate this acid to a proper state for crystalr 

 lization, it is sufficient to combine it with acetate of lime, and 

 to decompose this salt slightly calcined, by concentrated sul- 

 phuric acid. At the instant of contact the reaction is extremely 

 rapid, and the acetic acid is disengaged, giving up to the sul- 

 phate of lime all the superfluous water. 



The waters from the first and second crystallization of 

 the acetate of alkali are no longer susceptible of giving fresh 

 crystals by evaporation. As that, no doubt, depends on the 

 too great quantity of oily matter which is in it, it is i)robable that 

 bv calcining them alone, or with a mixture of charcoal powder, 

 or perhaps by making them boil with charcoal, they might again 

 acquire the properties of crystallization. 



Being evaporated to dryness, tliey are n)ixed with tar, and then 

 serve as fuel to heat the cauldron?;. But as the cinders from them 

 are not quite deprived of the acetate of alkali, they are passed 

 through a reverberating furnace, washed in lye, and by the second 

 crystallization the finest subcarbonate of alkali is obtained. 



L*XXVIII. On 



