SYNTHETIC WORK IN CARBOHYDRATES 339 



biose, triose, and tetrose sugars. These compounds contain, 

 respectively, as their names indicate, 2, 3, and 4 carbon atoms. 

 The latest addition to this list is the number containing the 

 smallest number of carbon atoms. This is a compound with 

 two atoms of carbon, chemically known as glycol-aldehyde, 

 and may be obtained from brom-acetaldehyde, by means of 

 barium hydrate in the cold. This compound possesses all the 

 properties to be expected from a simple sugar. Of these, the 

 property of being converted by phenylhydrazine into the gloxa- 

 losazone may be mentioned. It has not been possible to obtain 

 the glycol-aldehyde jrom admixture with the brom-aldehyde 

 from which it is derived; consequently, the behavior of this 

 simple sugar with ferments has not been proven. Since brom- 

 compounds act as a poison towards yeast, the mixture will 

 probably be found not to ferment. 



Triose or glycerose is considered to be a mixture of glyce- 

 rine aldehyde (CHOH . CHOH . CHO) and dioxyacetone 

 (CHOH . CO . CHOH). This compound is a syrup, and re- 

 duces Fehling's solution, and actively ferments with yeast. 



The chemical sugar next higher in the scale is the tetrose 

 sugar, which is formed by the oxidation of erythrit, and is 

 named therefrom erythrose. This is likewise a mixture of alde- 

 hyde and ketone compounds. The regeneration of this sugar 

 from its osazone has not as yet been accomplished. The syn- 

 thetical tetrose probably arises by a -kind of aldol condensa- 

 tion. It has been isolated in form of its osazone only, which 

 is identical with the erythrosazone. 



It may be mentioned in reference to aldol condensation, 

 that it is of two kinds. The condensation may be accompanied 

 either by the loss of a molecule of water or by no loss of water. 

 The former is known as aldehyde condensation, when, for 

 example, two molecules of ethylaldehyde are heated with zinc 

 chloride, and a molecule of water is lost. In the latter case, 

 the aldehyde must stand for a longer time with dilute hydro- 

 chloric acid; thence arises a condensation product known as 

 aldol condensation. 



The distinctions between the sugars characterized as the 

 aldose and ketose sugars disappear when these sugars are 



