FORMIC ALDEHYDE. 101 



19. Cerotic acid, C^H^O 2 . In beeswax as a free acid. 

 As ceryl ether in Chinese wax. 



20. Melissic acid, C 30 H 60 2 . Results from heating 

 myricyl alcohol with soda-lime. Has not been detected 

 in nature. 



D. ALDEHYDES, C n H 2n O. 



Aldehydes are compounds which occupy an inter- 

 mediate position between the primary alcohols and the 

 acids. They contain two atoms of hydrogen less 

 than the alcohols, and one atom of oxygen less than 

 the acids. They are produced by careful oxidation 

 of the primary alcohols, the group CH 2 .OH being 

 hereby transformed into the group CHO, which is com- 

 mon to all aldehydes. Hence, the aldehydes can also 

 be considered as derivatives of the hydrocarbons, 

 formed by the displacement of a hydrogen-atom by 

 the monovalent group CHO. By the action of hydro- 

 gen in statu nascendi, they are reconverted into the 

 primary alcohols ; under the influence of oxidizing 

 agents, they are readily changed to acids. They pos- 

 sess strong reducing properties. 



1. Formic Aldehyde (Methyl Aldehyde). 

 CH 2 = H.CliO. 



Formation. Is produced when the vapors of methyl 

 alcohol, together with air, are conducted over a plati- 

 num spiral, which at first is heated. The spiral be- 

 comes red and continues so during the operation. Is 

 further formed by subjecting gly colic acid, calcium 

 formate, or glycolate to dry distillation ; by treating 

 methylene iodide (see p. 36) with silver oxide or silver 

 oxalate. 



Properties. It appears that it can only exist at a 

 high temperature in the form of gas. At the ordinary 

 temperature, several (probably three) molecules com- 

 bine, forming a white, indistinctly crystalline mass, 

 oxymethylene C 3 H 6 3 , which sublimes below 100, fuses 



9* 



