1835.] Purification of Pyroligneous Acid, Sfc. 141 



have pure concentrated acetic acid. To accomplish this 

 the sulphurous acid in the distilled acetic acid should be 

 digested for a short time with finely pulverized brown-stone, 

 and a little wood or animal charcoal. One pound of brown- 

 stone and ^ pound of animal charcoal are sufficient for from 

 25to361bs. of acid. 



The supernatant liquid after the precipitate has been 

 allowed to subside during 12 hours should be decanted off, 

 transferred into a retort and rectified by a second distillation 

 to dryness. The acid passes over pure and colourless, and 

 destitute of any smell, save of acetic acid, having a specific 

 gravity of from 1-042 to 1*049, or 7° or 8° by Beck's 

 areometer, and may be used for all chemical purposes. 

 According to the custom of the trade, and of the French 

 manufacturers, a portionof acetic ether may be added to 

 the acid, by which mixture the smell becomes more pleasant. 



Supplement. — According to A. Richter, chemical manu- 

 facturer at Konigssaal, in Bohemia, with whom Prlickner 

 corresponded on this subject, it appears, that when the pure 

 acid, obtained by the process described, is neutralized by 

 carbonate of potash, and then some strong potash lye is 

 added, it still retains a yellow colour, from the presence of 

 an oxydizable body, of which it is difficult to free the acid. 

 Priickner, during the course of last summer, in his re- 

 searches, fell upon a method of affecting the separation of 

 this substance. 



Pyroligneous acid is not precipitated by infusion of galls, 

 and even after some time nothing falls. If however tincture 

 or infusion of galls be poured into a solution of pyroligneous 

 acid salt, as of raw acetate of lime (or acetate of potash) a 

 dark reddish purple precipitate subsides, which contains a 

 salt of tannic acid. The previously blackish brown liquid 

 becomes clearer and transparent like Rhenish wine, and 

 leaves after filtration and evaporation to dryness, by being 

 placed for several days in a temperature of 70° or 80° R. 

 (189° or 212° F.) a mass of salt, which, when compared 

 with the original salt, appears much lighter coloured. If 

 this is dissolved in water, or if the filtered liquid before 

 filtration is treated with some animal charcoal, the colour 

 of the salt becomes still lighter, and the odour is removed. 

 This salt of lime being diluted with i of sulphuric acid and 



