HYDROXY-, KETO- AND DIBASIC ACIDS to; 



Glycollic Acid. 



Glycollic acid is prepared by boiling potassium chloracetate under 

 a reflux condenser with water : 



CH 2 C1 . COOK + H 2 = CH 2 OH . COOH + KC1. 



The solution is evaporated in vacua to dry ness and the glycollic 

 acid extracted from the residue with acetone. 



It is present in unripe fruit and was first obtained from glycine. 

 Glycollic acid is a deliquescent crystalline solid which melts about 80. 

 It is a monobasic acid and at the same time a primary alcohol, and 

 consequently has the properties of both of these types of compounds. 



Glyoxal. 



Glyoxal can be prepared by oxidising acetaldehyde with nitric 

 acid at the ordinary temperature and is isolated as its bisulphite 

 compound. 



It is an amorphous solid, or when not quite free from water, a 

 syrup. It has all the properties of an aldehyde. 



Glyoxylic Acid. 



Preparation. 



Glyoxylic acid is prepared most conveniently by the reduction of 

 oxalic acid ; sodium amalgam was most frequently employed until 

 Benedict suggested the use of magnesium. 



About I gm. of powdered magnesium is placed in a small flask 

 and just covered with distilled water; 25 c.c. of saturated oxalic acid 

 solution are slowly added. The reaction proceeds rapidly with libera- 

 tion of heat and the flask should be cooled with water. The insoluble 

 magnesium oxalate, which is formed, is filtered off and the glyoxylic 

 acid is obtained by evaporation in vacuo. 



Properties. 



Glyoxylic acid is a syrup, very soluble in water. It gives the re- 

 actions of an acrd and of an aldehyde. 



The solution, prepared above, may be tested for aldehyde by 

 SchifTs reaction, ammoniacal silver nitrate and other reactions. It is 

 used in testing for proteins, the above solution being acidified with 

 acetic acid and made up to 100 c.c. with distilled water. 



