408* Intelligence and Miscellaneous Articles, 



ON THE SEPARATION OF CERTAIN ACIDS OF THE SERIES 

 O" H"^ O*. BY M. J. LIEBIG. 



When it is proposed to separate a mixture of butyric and valeric 

 acids, even when the quantities are small, the following process, 

 according to the author, may be employed :— 



Saturate a portion of the mixed acids with potash or soda, add 

 the remainder, and subject the whole to distillation. 



Two cases happen. If the mixture of valeric acid is contained in 

 larger quantity than requisite to saturate the whole of the alkali, 

 the residue no longer contains butyric acid, but pure valeric acid. 



If the quantity of valeric acid contained in the mixture is insuffi- 

 cient to saturate the alkali, the remainder contains, besides the whole 

 of the valeric acid, a certain quantity of butyric acid ; but the pro- 

 duct of the distillation consists of pure butyric acid. 



The quantity of alkali to be added to the mixture ought conse- 

 quently to be calculated according to the quantity of valeric acid 

 "which it is supposed to contain. If the mixture contains 10 per 

 cent., one-tenth of the acid should be saturated. If it be required 

 to separate 10 per cent, of butyric acid from impure valeric acid, 

 nine-tenths of the mixture must be saturated. 



From what is now stated, it is easy to perceive that one operation 

 is sufficient to obtain one of the acids in a pure state. Either the 

 product of the distillation is pure butyric acid, and the residue con- 

 tains a mixture of valeric acid and butyric acid, or the product of 

 the distillation contains a mixture of butyric and valeric acids, and 

 then the product is pure valeric acid. 



In repeating the same operations on the residue or the product of 

 the distillation performed, there is again obtained a certain portion of 

 one of the acids in a pure state ; and by continuing these saturations 

 and distillations, a complete separation of the acids may be effected. 



As the boiling-points of butyric and valeric acids differ, it might 

 be su])posed that soda, when combining with the less volatile acid, 

 would prevent its volatilizing at the temperature at which the other 

 boils. In fact, when in a mixture of valeric or butyric acids, the 

 first of these acids is fixed, it is evident that the second may distil 

 in a state of purity. 



A mixture of valeric and acetic acids, or of butyric and acetic 

 acids, behaves in a totally different manner. When such a mixture 

 is partially saturated with potash and submitted to distillation, it is 

 not the acetic acid which passes over, as might be supposed, but the 

 two other acids, although the point of ebullition of acetic acid is 

 lower by more than 50° than that of butyric acid, and by more than 

 70° than that of valeric acid ; in this case an acid acetate is formed 

 "which is not decomposed by the two less volatile acids. 



If valeric acid be added to a neutral solution of acetate of potash, 

 the acid dissolves in large quantity ; whereas it remains in the state 

 of oily drops in a solution of acid acetate of potash, in which it does 

 not appear to dissolve in larger quantity than in water. 



When valeric acid is added in excess to a neutral solution of ace- 



