198 Dr. Debus oti the Action of Nitric Acid on Glycerine. 



Glyceric Acid. 



In order to prepare tliis substance, a quantity of glycerate 

 of lime is dissolved in water and tbe lime precipitated by its 

 equivalent of oxalic acid. If the exact quantity of the latter, as 

 required by calculation, be taken, no oxalic acid or lime can be 

 discovered'in the liquid. With this agrees the following experi- 

 ment : — 



6-001 grms. of glycerate of lime were precipitated with 2'643 

 grms. oxalic acid. The precipitate gave in the usual way 2*095 

 grms. carbonate of lime. Consequently from 100 parts of gly- 

 cerate of lime 13-96 'parts of calcium were precipitated in the 

 shape of oxalate. The salt contains 13-98 parts of calcium. 



The filtrate from the oxalate of lime which contained the gly- 

 ceric acid was evaporated on the water-bath until it assumed 

 the consistency of syrup, and then placed over sulphuric acid for 

 a few days. No crystals could be obtained. Some of the syrupy 

 acid was dried at temperatures commencing with 100° C. and 

 rising gradually to 140'^ C. In this manner a substance of a 

 light brownish colour, and of the appearance of gum-arabic, was 

 obtained. 



Glyceric acid thus prepared is highly hygroscopic. A few 

 grains exposed in a platinum crucible to the atmosphere for some 

 hours, became quite liquid. Heated on a piece of platinum-foil 

 it melts, gives off acid fumes, and burns after a short time with 

 a bright flame. The solution of glyceric acid in water has a very 

 pleasant acid taste, similar to tartaric acid ; it decomposes the 

 carbonates, coagulates milk, and dissolves zinc and iron. From 

 the iron solution, caustic potash does not completely precipitate 

 the metallic oxide. 



A solution of sulphate of copper added to glyceric acid along 

 with caustic potash does not produce a precipitate, provided the 

 potash is in excess. On boiling, a strong brown precipitate 

 is formed. The analytical results obtained with a substance of 

 such physical properties as glyceric acid cannot be expected to 

 be very exact. Before I attempted an analysis, it appeared ne- 

 cessary to obtain further information with regard to its purity. 

 Although made from perfectly pure materials, it had assumed 

 during its preparation a brownish colour. Were the acid still 

 what it was supposed to be, it ought to yield, on neutralization 

 with carbonate of lime, the well-crystallizing glycerate of lime. 

 Some solid glyceric acid, dried at 140° C, was dissolved in water 

 and saturated carefully m ith lime. On partly evaporating the 

 liquid, a crop of beautiful crystals, with all the properties of 

 glycerate of lime, was obtained. The dish containing them and 

 the mother-liquor was now placed under a bell-glass over evil" 



