500 CONSIDERATION OF CARBON COMPOUNDS. 



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 4 4- 2 = CH. 2 2 4- H 2 O, 

 Methyl alcohol. Formic acid. 



by the action of carbonic oxide on potassium hydroxide: 



KOH 4- CO ; KCHO 2 , 



Potassium formate. 



by the action of potassium hydroxide on chloroform : 

 CHCl a 4- 4KOH = 3KC1 4- 2H 2 O 4 KCHO 2 , 



by the action of potassium on moist carbon dioxide : 

 2CO 2 4- ttjO 4- 2K = KHCO 3 + 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 O 4 = CO 2 4- CH 2 O 2 . 

 Oxalic acid. Formic acid. 



It is also a product of the decomposition of sugar, starch, etc. 

 Formic acid is a colorless liquid having a penetrating odor, and a 

 strongly acid taste ; it produces blisters on the skin ; it is a powerful 

 deoxidizer, being, when thus acting, converted into carbon dioxide 



and water : 



CH 2 O 2 + O = C0 2 4- H 2 0. 



Acetic acid, H.C 2 H 3 O 2 , or C 2 H 3 O.OH, or CH 3 .CO 2 H = 59.58. 

 The most important alcohol is ethyl alcohol, and the most largely 

 used organic acid is acetic acid, obtained from ethyl alcohol by oxi- 



