MONOBASIC FATTY ACIDS. 281 



Properties. Organic acids show the characteristics mentioned 

 for inorganic acids, viz., when soluble, have an acid or sour 

 taste, redden limus, and contain hydrogen, replaceable by metals 

 with the formation of salts. 



Most organic acids, and especially the higher members, show 

 these acid properties in a less marked degree than inorganic 

 acids ; in fact, they become so weak that the acid properties can 

 often scarcely be recognized. As stated above, mono-, di-, and 

 tribasic organic acids are known, the two latter being capable 

 of forming neutral, acid, or double salts. 



Most organic acids are colorless, some of the lower and 

 volatile acids have a characteristic odor, but most of them are 

 odorless; most organic acids are solids, some liquids, scarcely 

 any gaseous at the ordinary temperature. Any salt formed by 

 the union of an organic acid and a non-volatile metal (especially 

 alkali metal) leaves the carbonate of this metal upon heating 

 the salt sufficiently for combustion. It is for this reason that 

 ashes contain most metals in the form of carbonates. 



"Whilst the h} 7 drogen of the hydroxyl may be replaced by 

 metals or by other residues, the hydrogen of the acid radical 

 may often be replaced by chlorine, and the oxygen of the 

 hydroxyl by sulphur. 



When the hydrogen of the hydroxyl is replaced by a second 

 acid radical (of the same kind as the one forming the acid) the 

 so-called anhydrides are produced, which correspond to the inor- 

 ganic anhydrides. For instance: 



HNO 3 or NO 2 .HO C 2 H 4 O 2 or C 2 H 3 O.HO. 



Nitric acid. Acetic acid. 



NO,\ C 2 H 3 O\ 



N(V CXO/ 



Nitric anhydride. Acetic anhydride. 



Fatty acids of the general composition, C n H. )n 2 or C n H., n + jCOoH. 



Fining-point. Soiling-point. Occurs in : 



Formic acid -j-4 100 Red ants and some plants, etc. 



Acetic acid, +17 118 Vegetable and animal fluids. 



Propionic acid, 21 140 Sweat, fluids of the stomach, etc. 



Butyric acid, '20 162 Butter. 



Valerianic acid, 16 185 Valerian root. 



Caproic acid, 2 205 Butter. 



(Enanthylic acid, 10 224 Castor oil. 



Caprylic acid, +14 2S6 Butter; cocoanut oil. 



