SYNTHETIC WORK IN CARBOHYDRATES 321 



the aldehyde sugars. As a comprehensive name for the class, 

 the word aldose has been adopted. The other class of sugars 

 is known as the ketose sugars, so called from the ketone group 

 (CO), or carbonyl, contained in their molecules. 



The ease with which formaldehyde polymerizes, under fa- 

 vorable conditions, qualifies this compound eminently for its 

 function in sugar-formation. 



Polymerization is the amalgamating, so to speak, of two or 

 more aldehyde groups, forming a carbon compound contain- 

 ing a greater number of carbon atoms. 



In considering the polymers of formaldehyde, Baeyer sug- 

 gested that, under the influence of the contents of the plant 

 cells, 6 molecules of formaldehyde polymerize to form i mole- 

 cule of glucose, 6HCHO=C 6 H 12 O 6 . 



It has been claimed that formaldehyde occurs in plants, 

 and has been found in very small quantities in plant cells; but 

 in any great proportion it acts as a poison to the living plant, 

 and Fischer has suggested, in consequence, that there can be 

 no doubt that other intermediary compounds occur in the 

 formation of sugars. Bokorny 1 has made an interesting ob- 

 servation on the assimilation by the green cells of Algae of a 

 double compound of formaldehyde and sodium bisulphite. 

 He has shown that, if plants are deprived of starch and placed 

 in an atmosphere free from carbonic acid, they are capable 

 of forming considerable quantities of starch under the influ- 

 ence of sunlight, if fed upon this compound. In the dark the 

 conversion of formaldehyde into starch does not take place. 



Low, by treating formaldehyde with lime, obtained a sugar 

 which he called formose. Fischer has shown that this pro- 

 duct contains sugar compounds of the composition C 6 H 12 O 6 , 

 and among these, one named acrose, which stands in very 

 close relation to natural glucose. 



It may be well to state here that the term sugar includes a 

 variety of substances. It includes fruit sugar, glucose, and 

 chemically allied sugar groups, some of which contain more 

 and some less carbon atoms than glucose. These compounds 

 are not to be confounded with the food material derived from 



1 Landiv. Jahrbwh, xxi, 445. 



