FUMARIC ACID. 165 



nitric acid of specific gravity, 1.2. Shining, lamellar 

 crystals ; more easily soluble in ether than suberic 

 acid, more difficultly than azelaic acid ; fusing point, 

 127-128. 



9. Brassylic acid, C n H 20 O. As yet it has only been 

 obtained from behenolic acid together with the oily 

 aldehyde C n H 20 3 . Colorless scales, difficultly soluble 

 in water, even at the boiling temperature ; fusing 

 point, 108.5. 



10. Roccellic add, C 17 H 32 4 . As yet, it has not been 

 prepared artificially. Occurs in Roccella tinctoria, and 

 can be extracted from it by ammonia or ether. Colorless 

 prisms, insoluble in water, soluble in alcohol and ether ; 

 fusing point, 132. 



D. BIBASIC, DIATOMIC ACIDS, C n H 2n ~ 4 4 . 



The acids of this series are derived from the hydro- 

 carbons of the ethylene series in the same way as the 

 acids of the oxalic acid series are derived from the 

 hydrocarbons of the marsh gas series. 



1. Fumaric Acid. 



P 2 TT 



L 



a . OH 



CO.OH. 



Occurrence. In a great many plants ; in Fumaria 

 officinalis, Corydalis bulbosa, Glaucium, luteum, in Ice- 

 land moss and several- fungi. 



Formation and preparation. When chlorous acid or 

 potassium chlorate and dilute sulphuric acid are al- 

 lowed to act on benzol, there is produced, together with 

 other bodies, an acid, trichlorphenomalic acid C 6 H 7 C1 3 5 , 

 which crystallizes well and fuses at 131-132. When 

 this is boiled with baryta water, barium fumarate is 

 formed, from which by exact precipitation with sulphuric 

 acid the free acid is obtained. From dibromsuccinic acid 

 and isodibromsuccinic acid by heating with potassium 



