146 GLYCOLIC ACID. 



Properties. Deliquescent crystals ; easily soluble in 

 water, alcohol, and ether; fuses at 78-79. When 

 subjected to distillation, it undergoes decomposition, 

 yielding formic aldehyde (oxymethylene, p. 101). 



The calcium salt (C 2 H 3 3 ) 2 Ca forms fine, needly crys- 

 tals, difficultly soluble in cold water ; the silver salt 

 C 2 H 3 3 Ag + JH 2 0, lustrous crystals, also difficultly 

 soluble. 



Glycolic acid is acetic acid in which one atom of 

 hydrogen is replaced by hydroxyl. The hydrogen of 

 this OH cannot be replaced by metals by treatment 

 with bases, but easily by alcohol and acid radicals. A 

 number of such compounds, for instance, methylglycolic 

 acid CH 2 (O.CH 3 )CO.OH (from sodium chloracetate and 

 sodium methylate ; colorless, thick liquid, boiling at 

 198), ethylglycolic acid CH 2 .(O.C 2 H 5 ).CO.OH (liquid, 

 boiling at 206-207), are known ; and all these com- 

 pounds, like gly colic acid, are monobasic acids. 



CEP.O. CH 2 

 Diglycolic acid, C 4 H 6 5 + H 2 = Q OH( j OH 



Is produced as a secondary product in the preparation 

 of glycolic acid from monochloracetic acid and by the 

 oxidation of diethylene alcohol (p. 138). Large, color- 

 less, monoclinic crystals. Easily soluble in water and 

 alcohol. Fuses below 150 ; bibasic acid ; isomeric with 

 malic acid. 



Glycolid (Glycolic anhydride), C 2 H 2 2 = 

 CH 2 | QQ^> is formed by heating glycolic acid, or 



potassium chloracetate ; or by heating tartronic acid to 

 180. White, amorphous powder; is converted into 

 glycolic acid by boiling with water or alkalies; by 

 heating with ammonia, into glycolamide C 2 H 5 N0 2 = 

 CIP.OH.CO.NH 2 (isomeric with glycocol). Colorless 

 crystals, fusing at 120. 



