84 THE VEGETABLE ACIDS [ ch. 



Malonic acid has been isolated from the Sugar Beet {Beta vulgariif 

 var. Rapay, It forms insoluble calcium and lead salts. 



Succinic acid is probably widely distributed in plants. It has been 

 isolated from the unripe Grape, from fruit of the Gooseberry, Currant, 

 Apple and Banana, from Rhubarb {Rheum Rhaponticum), Greater 

 Celandine {Chelidonium majus) and other plants. Succinic acid crystallizes 

 well in rhombic prisms or plates. It is not very readily soluble in cold 

 water, though more so in hot. Its salts with the alkali metals are readily 

 soluble. Calcium succinate is deposited as acrystalline precipitate on adding 

 calcium chloride to fairly concentrated solutions of the acid after neutrali- 

 zation (or of a soluble succinate), but from a dilute solution it is not 

 precipitated except on addition of alcohol. Barium succinate comes 

 down as a crystalline precipitate even from dilute solutions. Ferric 

 succinate is insoluble and its formation is used in the detection of the 

 acid. 



The relationship of succinic acid to aspartic, or a-amino-succinic, acid 

 which is an abundant constituent of many proteins (see p. 134) should be 

 noted. 



Expt. 83. Tests for succinic acid. A. Take a 1 % solution of succinic acid> 

 neutralize with caustic soda (or use a soluble succinate) and make the following tests : 



(a) To 5 c.c, add a few drops of 5 ^q calcium chloride solution. A slight precipitate 

 is formed, especially on rubbing the sides of the tube with a rod. To another 5 c.c. 

 add again calcium chloride solution followed by an equal volume of 96 % alcohol. 

 A white precipitate of calcium succinate is formed. 



(6) To 5 c.c. add a few drops of 5 % barium chloride solution. A crystalline 

 precipitate of barium succinate is formed and, again, its appearance is hastened by 

 rubbing the sides of the tube. 



(c) To 5 c.c. add a few drops of 5 7o lead acetate solution. A white precipitate of 

 lead succinate is formed. Add an equal quantity of strong acetic acid. The pre- 

 cipitate is soluble. 



{d) To 10 c.c. add about 1-2 c.c. of 5% ferric chloride solution. A red-brown 

 gelatinous precipitate of ferric succinate is formed. Filter oflf the precipitate, wash 

 well and boil with about 20 c.c. of dilute ammonia. Filter off the ferric hydroxide, 

 and to the filtrate, after boiling off any excess of ammonia, add 5 % barium chloride 

 solution. A crystalline precipitate of barium succinate is formed. This test con- 

 stitutes a method for identifying succinic acid. 



B. Make a cold concentrated solution of succinic acid, neutralize (or use a soluble 

 succinate) and add 5 ^Jq calcium chloride solution. A crystalline precipitate of calcium 

 succinate will separate out. Its appearance may be hastened by rubbing or shaking. 



1 It should be noted that an exceptionally large number of chemical substances have 

 been isolated from the Sugar Beet on account of their accumulation in the waste products 

 from sugar manufacture. There is little doubt that the same substances could be isolated 

 from other plants if sufficient quantity of material were employed. 



