On reduction glucose appears to yield the hexahydric alcohol d-sorbite, and on oxidation d-gluconic and d-saccharic acids.
Since both d-glucose and d-gulose yield the same active (d) saccharic acid on oxidation, the configuration of this and the corresponding /-acid must be sought from among those numbered 5-10 in the above table.
7 and 8 can be at once ruled out, however, as acids so constituted would be optically inactive and the saccharic acids are active.
If the configuration of d-saccharic acid were given by either 6 or To, bearing in mind the relation of mannose to glucose, it would then be necessary to represent d-mannosaccharic acid by either 7 or 8 - as the forms 6 and Io pass into 7 and 8 on changing the sign of a terminal group; but this cannot be done as mannosaccharic acid is optically active.
5, therefore, represents the configuration of one of the saccharic acids, and No.
When heated to about 200° it yields a brown amorphous substance, named caramel, used in colouring liquors, &c. Concentrated sulphuric acid gives a black carbonaceous mass; boiling nitric acid oxidizes it to d-saccharic, tartaric and oxalic acids; and when heated to 160° with acetic anhydride an octa-acetyl ester is produced.
It is oxidized by nitric acid to d-saccharic and mucic acids; and acetic anhydride gives an octa-acetate.
The best instruments are now constructed for revenue purposes of silver, heavily gilded, because it was found that saccharic acid contained in some spirits attacked brass behind the gilding.
It may also be obtained (together with racemic acid) by oxidizing milk sugar, saccharic acid, &c., with nitric acid, and by the reduction of oxalic ester with sodium amalgam (H.