FATS. 



/ / 



subsequent crystallizations are nearly pure butyrate of baryta, 

 which is purified by recrystallization. 



" The saline mass of difficult solution is dissolved in just so 

 much boiling Avater as is requisite for complete solvition, arid is 

 filtered while hot. During the cooling, the liquid becomes filled 

 with minute scales of caprate of baryta, of a fatty lustre, which 

 subside in the form of a crystalline precipitate. The decanted 

 mother-ley is again evaporated one fourth, when a fresh quan- 

 tity of caprate of baryta separates. This salt is purified by re- 

 crystallization. The mother-ley now contains the capiyllate in 

 solution ; it is evaporated by exposure to the sun, when the salt 

 separates in minute granules and verrucous masses, which are 

 obtained pure by recrystallization. 



" This is the best method of separating these salts from each 

 other ; an absolute separation is impossible, for there always re- 

 main mixed crystals and leys, which in small quantities are not 

 worth while working."^ 



The but^a-ate of baryta is much the most soluble of these 

 salts, requiring only 2-77 parts of water. On decomposing it 

 by adding dilute sulphuric acid to its solution we obtain butyric 

 acid, in the form of a colourless or faintly yellow oleaginous 

 fluid. 



Butyric acid possesses an unpleasant odour, which calls to 

 mind at the same time that of acetic acid and of rancid butter. 

 It is soluble in every proportion in water and alcohol, and more 

 soluble in ether than the other acids of the same group. Its 

 specific gravity is 0-963 at 59" ; it evaporates easily in the open air, 

 boils under ordinary pressure at about 337°, and distils without 

 undergoing any perceptible alteration. Its vapour is inflam- 

 mable, and burns with a blue flame. A continued cold of 4" 

 does not produce any change in the state of the butyric acid ; 

 its taste is strongly acid and burning ; it attacks and disorga- 

 nizes the skin in the same manner as the strongest acids. 



The chemical relations of this acid have been made an object 

 of especial research by Chevreul, Pelouze and Gelis, and Lerch ; 

 and numerous butp-ates and butyric ether have been formed, 

 and submitted to careful investigation and analysis. 



' Ann. der Chem. und Pharm. xlix, j). 212, as translated in Number 45 of the 

 Chemical Gazette. 



