1836.] Purification of Pyroligneous Acid, ^c. 139 



mixture well up by means of a wooden spatula. This pre- 

 paration should be made in the evening, and the mixture 

 allowed to stand till the morning. On the following day 

 20 lbs. of English sulphuric acid, diluted with 5 lbs. of water 

 should be added, and the cover of the retort cemented. 



The cover should be made of pure tin, and united with a 

 refrigatory, whose tube is also formed of the same metal. 

 Priickner considers porcelain preferable to tin for the com- 

 position of the cover, or rough burned clay (nicht durck- 

 switzender), the latter of which he himself employs. 



To prevent the melting of the tin, when that metal is 

 employed, it is necessary to separate it from the iron of the 

 retort by means of a stripe of linen ; a luting of lime and 

 fine sand then serves to unite the cover and belly of the 

 retort. Larger retorts are not desirable, because, towards 

 the end of the distillation, decomposition of the acetic acid 

 is readily produced, in consequence of the destruction which 

 a portion of the mass in contact with the bottom undergoes, 

 while all the acid contained in it is driven off. The distilla- 

 tion begins with a gentle fire, and should be carried on 

 without increasing the heat, until the liquid passing over 

 begins to produce a yellowish colour in the distilled liquid. 

 It is not worthwhile to obtain the last portions of the acid, 

 because the educt is impure, and sulphur begins soon to 

 sublime. 



From the 25 lbs. of acetate of lime are obtained 25 to 27 

 parts of acid. The gypsum remaining in the retort can be 

 easily removed. It contains some free acid, which may be 

 washed out and preserved for further use. By the action 

 of the sulphuric acid upon the acetate of lime, a sulphurous 

 smell will be perceived, which also exists in the weak acid 

 which passes over first. This arises from a partial decom- 

 position of the sulphuric acid, in consequence of which 

 sulphurous acid is disengaged. 



To diminish, as much as possible, the quantity of this in 

 the whole distilled liquid, the first tenth is removed. The 

 subsequent distillation is continued until the liquor passing 

 over begins to lose its pure water colour. The last portions 

 will, therefore, be separated and mixed with the acid which 

 passed over first, for the purpose of being further purified. 



The acid obtained in the manner described, possesses 



