MONOBASIC FATTY ACIDS. 325 



Omrstn: 



Palmitic acid, C 15 H 31 CO 2 H 62 ..... Palm oil, butter. 



Margaric acid, C 16 H 33 CO 2 H 60 ..... (Obtained artificially.) 



Stearic acid, C 17 H 35 CO 2 H 70 ..... Most solid animal fats. 



Arachidic acid, C 19 H 39 CO 2 H 75 ..... -| 



Behenic acid, C 21 H 43 CO 2 H 76 ..... j- Oils of certain plants. 



Hysenicacid, C 24 H 49 CO 2 H 77 ..... J 



Ceroticacid, C 26 H 33 CO 2 H 80 ..... 1 Beeswax 



Melissic acid, C^H^CO^H. 90 ..... / 



The name fatty acids has been given to these acids on account of 

 their frequent occurrence in fats, and also in allusion to the some- 

 what fatty appearance of the higher members of the series. 



The gradual change of properties which the members of an homol- 

 ogous series show, is well marked in the series of fatty acids, thus: 



First member. Last member. 



Is liquid. Is solid. 



Volatilized at 100 C. Not volatilized without decomposition. 



Strongly acid. Scarcely acid. 



Strongly odoriferous. Odorless. 



Easily soluble in water. Insoluble in water. 



Produces no grease spot. Produces a grease spot. 

 Forms salts easily soluble without Forms salts which are insoluble or de- 

 decomposition. composed by water. 



The intermediate members of the series show intermediate proper- 

 ties, and this change in properties is in proportion to the gradual 

 change in molecular weight. 



Formic acid, H.CO 2 H or CHO.OH. This acid is found in the 

 red ant and in other insects, which eject it when irritated. It is also 

 contained in some plants, as, for instance, in the leaves of the sting- 

 ing nettle. 



It is formed by the oxidation of methyl alcohol : 



CH 3 + 2 = CH,0 2 + H 2 0, 

 Methyl alcohol. Formic acid. 



by the action of carbonic oxide on potassium hydroxide : 



KOH + CO = KCHO 2 , 



Potassium formate. 



by the action of potassium hydroxide on chloroform : 

 CHC1 3 4- 4KOH == 3KC1 + 2H 2 O -f- KCHO 2 , 



by heating equal parts of glycerin and oxalic acid, when the latter is 

 split up into carbon dioxide and formic acid, which may be separated 

 from the glycerin by distillation : 



C 2 H 2 4 : C0 2 + CH 2 2 . 



Oxalic acid. Formic acid. 



