434 Notes on Organic Chemistry. 



elements, are in general carbides* of hydrogen. Sometimes they 

 are formed of carbon and hydrogen in equal equivalents, as in 

 the series of carbides which are most important in organic 

 chemistry; at other times, the number of hydrogen equiva- 

 lents dominates ; and in other and more frequent cases, the 

 number of carbon equivalents is most considerable. As ex- 

 amples of these different carbides, I shall cite in the first 

 series olefiant gas, C 4 H 4 ;f i n the second group, marsh gas, 

 C 2 H 4 ; in the third, benzine, C 13 H B ; spirits of turpentine, C 20 , 

 H 16 , etc., etc. 



From this group we pass to compounds of three elements, 

 carbon, hydrogen, and oxygen, which are extremely numerous. 

 They comprehend " the alcohols, fatty bodies, neutral, and 

 acid ; acetic acid, essence of bitter almonds, etc., etc. Some- 

 times the three elements are combined in equal proportions of 

 their equivalents, as in grape sugar, C 13 , H 13 , O 13 , and acetic 

 acid, C 4 , H 4 , O 4 ." Most frequently they contain unequal num- 

 bers of equivalents, as in oxalic acid, C 4 , H 2 , s ; but in general 

 carbon and hydrogen predominate, as in alcohol, ether, stea- 

 rine, etc. 



" Ternary compounds, containing nitrogen, that is to say, 

 bodies composed of carbon, hydrogen, and nitrogen, are much 

 less numerous than the preceding. Among them is aniline, J 

 C 13 , H 7 , Az;§ Nicotine, C 20 ,H 14 , Az 3 , etc. 



Still more complicated are the quaternary bodies, or bodies 

 formed of four elements. " They are frequently of animal 

 origin. This group contains fibrin, albumen, urea, uric acid, 

 etc. Almost all the vegetable alkalies belong to this group." || 

 Besides these we have a limited number of bodies still 

 more complicated by the addition of sulphur or phosphorus, 

 the latter existing in one of the constituents of nerve matter. 



A complicated organic substance may be resolved into its 

 elementary constituents by chemical processes that involve its 

 destruction. But by another set of chemical processes, certain 

 elements may be removed, either wholly or partially, and then 

 the compound is changed, but not destroyed. Elements that 

 are thus removed may be replaced by others, and then the 

 compound is changed again, but not destroyed. The principal 

 complicated substances composing or formed by an organic 

 body, may be reduced to certain types, and arranged in series, 

 so that we see how, by changes and transpositions of the sort 



* Carbides, formerly called carburet?, are compounds of carbon with another 

 substance. 



t C. means carbon, H. hydrogen, and the figures give the number of equi- 

 valents. 



X The base of the beautiful dyes so called. 



§ Az. means Azote, or nitrogen. 



|| A substance found in opium. Op. cit., page 22. 



