84 ANIMAL CHEMISTRY LECTURE IV. 



Starting from the I -carbon or methyl-alcohol, we can convert 

 it into the 2-carbon or acetic acid by well-known processes. But 

 in order to proceed from the z-carbon acid, we must first trans- 

 form it into the 2-carbon alcohol the alcohol, in some or other 

 of its forms, being the synthetic starting-point, so to speak and 

 this we have very recently learned to do. Then, by affixing 

 deoxidised carbonic anhydride on to the 2-carbon alcohol, we 

 convert it into the 3 -carbon or propionic acid. Then by acting 

 upon propionic acid by deoxidised water, we transform it into 

 3 -carbon or propyl-alcohol, upon which we again affix deoxidised 

 carbonic- anhydride to convert it into the 4~carbon or butyric 

 acid, and so on continuously, by a series of deoxidising actions 

 with carbonic oxide and hydrogen alternately. 



(88.) Now let us proceed to notice briefly, in the order of their 

 complexity, some of the more interesting organic or carbon com- 

 pounds which have been produced artificially by elementary syn- 

 thesis. Among mono-carbon compounds, we have first carbonic 

 acid CH 2 3 , alike the most important product of animal oxidation 

 and subject of vegetable deoxidation. Associated with carbonic 

 acid or hydrate, we have carbonic amide or urea CH 4 N 2 O, a 

 body standing towards carbonic acid in the same relation that 

 ammonia stands to water, and convertible into carbonic acid by 

 an exchange of certain elements of ammonia for the corresponding 

 elements of water, thus : 



Urea Water Ammonia Carbonic acid 



, + (H,)H,0, = (H a )H 4 tf a + (CO)"H a O a 



Carbonic acid is likewise met with in its dehydrated form as car- 

 bonic anhydride CO 2 , and as the sulphur derivative of that body 

 or carbonic sulphide CS 2 . These compounds are obtainable by 

 burning charcoal in oxygen and sulphur respectively, the last of 

 them, under the name of disulphide of carbon, being now pro- 

 duced on an enormous scale for certain manufacturing uses. 

 Moreover, by the dehydration of carbonic acid, a substance that 

 is known only in the state of solution, we also produce carb- 

 anhydride, as shown in the following equation 



