GLYCOLIC ACID. 145 



there can exist just as many isomeric modifications, as 

 of the monochlorine- or monobromine-substitution-pro- 

 ducts of the corresponding fatty acid ; of the first 

 member only one; of the second two, CH 2 (OH).CH 2 .CO. 



OH and CH 3 .CH j Q etc. 



1. Gly colic Acid (Oxy acetic Acid). 



Occurrence. In unripe grapes. 



Formation and preparation. By heating potassium 

 chlor- or bromacetate with water, or by the addition 

 of silver oxide to a hot aqueous solution of chlor- or 

 bro mace tic acid ; by the action of nascent hydrogen 

 (from zinc and sulphuric acid) on oxalic acid or oxalic 

 ether ; by treating glycocol with nitrous acid ; and by 

 careful oxidation of ethylene alcohol. Can be most 

 readily obtained by slow oxidation of ethyl alcohol. 

 A mixture of 500 grms. alcohol and 440 grms. nitric 

 acid is allowed to stand in cylinders, which are imper- 

 fectly closed, until small gas bubbles begin to appear 

 in the liquid: the cylinders are then placed in water 

 of 20. In a few days the action is completed. The 

 solution is now evaporated in small portions to a 

 syrupy consistence, dissolved in water, neutralized 

 with chalk and allowed to crystallize. The calcium 

 glycolate, thus obtained, must be again dissolved and 

 boiled for some time with milk of lime, for the pur- 

 pose of decomposing any secondary products which 

 may be present (glyoxal, glyoxylic acid). The solution 

 is treated with oxalic acid in order to set the acid free, 

 the filtrate from calcium oxalate almost neutralized 

 with lead carbonate, and the solution of the lead salt 

 evaporated to crystallization. From the solution of 

 this salt, the lead is removed by means of sulphuretted 

 hydrogen or, still better, sulphuric acid, which is 

 added in not quite sufficient quantity to complete the 

 decomposition, the filtrate evaporated and the gly colic 

 acid extracted by means of anhydrous ether. 

 13 



