STEARIC ACID. 109 



which acid fermentation has with all due caution been established, 

 the most beautiful crystals of margaric acid are formed ; more 

 beautiful indeed than we could artificially prepare. 



We shall postpone our observations regarding the origin of 

 margaric acid in the animal organism, and the rank and position it 

 holds in the metamorphosis of the animal tissues, till we take into 

 consideration the formation and the physiological importance of 

 the fats in the animal body. 



STEARIC ACID. C 68 H 66 O 5 .2HO. 



Chemical Relations. 



Properties. This acid crystallises in white, glistening needles 

 or leaflets, which, however, under the microscope, appear as very 

 elongated, lozenge-shaped plates, with the obtuse angles rounded 

 off, as in the microscopical whet- stone-like crystals of uric acid ; 

 these crystals are, however, much longer, and have a far shorter 

 transverse diameter than the similar crystals of uric acid. They 

 often collect at one spot, the acute angles slightly overlapping one 

 another, so that when seen under the microscope the crystals 

 present the arrangement of whorl-shaped clusters. This acid begins 

 to fuse at 75, but again solidifies if the temperature is reduced 

 to 70. Submitted to dry distillation it yields hydrated margaric 

 acid, margarone, and an oleaginous carbo-hydrogen ; by prolonged 

 digestion with nitric or chromic acid it becomes perfectly converted 

 into margaric acid. In the cold, stearic acid decomposes the car- 

 bonated alkalies to the amount of one-half, but with the aid of heat 

 a perfect decomposition is effected. 



Composition. According to the above formula, stearic acid 

 contains : 



Carbon .... .... 68 atoms .... 76'692 



Hydrogen .... 66 .... 12'406 



Oxygen 6 .... 7'519 



Water 2 .... 3-383 



100-000 



The atomic weight of the hypothetical dry acid =6425 : its 

 saturating capacity, (if we regard as neutral the salt containing 2 

 atoms of base) =3*113. 



Combinations. The neutral alkaline stearates (containing 2 



