THE ORGANIC NON-NITROGENOUS ACIDS. 93 



the vegetable alkaloids, with which they have many reactions in 

 common. They have strongly basic properties, and are capable of 

 combining with acids to form salts. Like the albumins from which 

 they are derived, they are precipitated with the chlorides of platinum, 

 mercury, and gold, as also with tannic acid, picric acid, phospho- 

 molybdic acid, phosphotungstic acid, etc. With these they form 

 well-defined crystalline salts, which serve for their differentiation 

 from each other and as a basis for the determination of their ele- 

 mentary composition. The methods which are employed for the 

 separation of ptomains will be considered in a subsequent chapter. 



THE ORGANIC NON-NITROGENOUS ACIDS. 



The organic non-nitrogenous acids which are formed in the animal 

 body are largely members of the fatty acid series. Others belong to 

 the glycolic series, still others to the acrylic series, some are repre- 

 sentatives of the oxalic series, and still others belong to the aromatic 

 oxy-acids. The first group comprises the following acids, which as 

 a class may be represented by the formula C n H 2n O 2 . 



Formic acid H.COOH = CH 2 O 2 



Acetic acid CH 3 .COOH = C 2 H 4 O 2 



Propionic acid CH 2 .CH 3 .COOH = CaH^ 



Butyric acid (CH 2 ) 2 .CH 3 .COOH = C 4 H 8 O 2 



Valerianic acid (CH 2 ) 3 .CH 3 .COOH = C 5 H 10 O 2 



Capronicacid (CH 2 ) 4 .CH 3 .COOH = C 6 H, 2 O 2 



Palmitic acid (CH 2 ) U .CH 3 .COOH = C 16 H 32 O 2 



Stearicacid (CH 2 ) 16 .CH 3 .COOH = C, 8 H 36 O 2 



The two last, as has been seen, are integral constituents of the 

 fats, in which they are present in combination with glycerin as tri- 

 glycerides. From these the others may in part be derived, but to 

 the greatest extent no doubt they result from the amido-acids 

 through a process of oxidation or reduction, as illustrated by the 

 equations : 



CH 2 (NH 2 ).COOH + 2O = H.COOH + NH 3 + C0 2 



Glycocoll. Formic 



acid. 



CH 2 (NH 2 ).COOH + 2H = CH 3 .COOH + NH 3 

 Glycocoll. Acetic acid. 



Through further oxidation these acids are then transformed into 

 those standing next in order in the downward scale, and so on, 

 until finally carbon dioxide and water result, as seen in the equations : 



(1) CH 2 .CH 3 .COOH + 30 = CH 3 .COOH + CO 2 + H 2 O 



Propionic acid. Acetic acid. 



(2) CH 3 .COOH -f 3O = H.COOH -f CO 2 -f H 2 O 



Acetic acid. Formic 



acid. 



(3) H.COOH -fO =C0 2 +H 2 O 

 Formic acid. 



To some extent, however, the fatty acids are derived also from lactic 

 acid and related acids, which, as will be seen later, are constantly 



