16 ANIMAL ACIDS DESTITUTE OF AZOTE. 



less, but by exposure to the air they become opaque. Yet the 

 silky crystals deposited from boiling alcohol retain their limpi- 

 dity and their other characters. 



The taste of cholic acid is bitter but weaker than that of bile. 

 It is very soluble in alcohol and ether ; but insoluble in water. 

 The solution reddens litmus paper, decomposes the carbonates 

 with effervescence, and neutralizes bases. When -the etherial so- 

 lution is rapidly evaporated, it leaves a deposit having a greasy 

 feel, showing that the acid belongs to the tribe of oily acids. 



It is fixed, burning with flame, giving out smoke, and leaving 

 a good deal of charcoal. 



The characters of the cholates are quite different from those 

 of the choleates and choloidates. They have not a resinous con- 

 sistence, do not melt in boiling water and dry easily. It is diffi- 

 cult to obtain them quite neutral. 



The cholates of potash and soda are soluble in water, while the 

 cholates of lime, barytes, zinc, copper, and silver are insoluble 

 in that liquid. They are readily decomposed into bisalts and 

 disalts. 



SECTION IX. OF PYROZOIC ACID. 



This name was applied by Berzelius to an acid formed when ani- 

 mal substances are distilled per se, Unverdorben,* who first exa- 

 mined its properties, distinguished it by the name of brandsaure. 



When an animal substance, glue, muscle, &c. is distilled 

 per se 9 the first product is carbonate of ammonia, partly dry 

 and partly dissolved in a brown-coloured liquid, which con- 

 tains a variety of substances besides. The second product 

 is an empyreumatic oil ; which is generally called Dippel's oil ; 

 because it was Dippel who first obtained it in a state of purity. 

 This oil in its crude state has a yellow or rather brown colour, 

 and contains a variety of bases, which will be described in a sub- 

 sequent part of this volume. The empyreumatic oil is mixed 

 with potash and distilled. The pyrozoic acid remains in com- 

 bination with the potash. The potash residue is diluted with 

 water and evaporated. And this process is repeated several 

 times to get rid of all the empyreumatic oil which it contains. 

 As soon as the smell of empyreumatic oil can no longer be per- 

 ceived, dilute sulphuric acid is added to the alkaline liquor as 

 long as a matter similar to tar continues to precipitate. It is 



* Poggendorf s Arinalen, viii. 262. 

 4 



