258 -CONSIDERATION OF CARBON COMPOUNDS. 



pounds formed by replacement of hydrogen in hydrocarbons by 

 carboxyl. Otherwise, organic acids have the general properties 

 of inorganic acids. 



5. Ethers. Compounds formed from alcohols by replacement 

 of the hydrogen of the hydroxyl by other unsaturated hydro- 

 carbons, or, what is the same, by other alcohol radicals. For in- 

 stance : 



C 2 H 5 .HO, C 2 H 5 .C 2 H 5 O, C 2 H 5 .CH 3 O. 



Ethyl Ethyl ether. Ethyl- 



alcohol. methyl ether. 



6. Compound ethers or esters. Formed from alcohols by re- 

 placement of the hydrogen of the hydroxyl by acid radicals, or 

 from acids by replacement of the hydrogen of carboxyl by 

 alcohol radicals. For instance : 



so 4- 3O 25O i 



/ U H/ U C L 



Ethyl Acetic acid. Acetic ether. Water. 



alcohol. 



The various fats belong to this group of compound ethers. 



7. Carbohydrates. (Sugars, starch, gum, etc.) These com- 

 pounds contain 6 atoms of carbon (or a multiple of 6) in the 

 molecule, and hydrogen and oxygen in the proportion of 2 atoms 

 of hydrogen to 1 atom of oxygen, or in the proportion to form 

 water. Most carbohydrates are capable of fermentation, or of 

 being easily converted into fermentable bodies. Instances : 

 C 6 H 12 6 , C 6 H 10 5 , etc. 



Glucosides are substances the molecules of which may be 

 split up in such a manner that several new bodies are formed, 

 one of which is sugar. 



8. Amines and amides. Substances formed by replacement of 

 hydrogen in ammonia by alcohol or acid radicals. For instance : 

 ethyl amine, NH 2 .C 2 H 5 , urea, N 2 H 4 .CO, etc. The alkaloids be- 

 long to this group. 



9. Cyanogen and its compounds. Substances containing the 

 radical cyanogen, CN. For instance : potassium cyanide, KCN. 



10. Proteids or albuminous substances. These contain, besides 

 carbon, hydrogen and oxygen, always nitrogen and sulphur, 

 sometimes also other elements. Instances: albumen, casein, 

 fibrin, etc. 



In connection with each of these groups have to be considered 

 the derivatives obtained from them directly or indirectly. 



