Glucose
2 of the 6 encyclopedias on this shelf carry an entry for Glucose. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
a fermentable sugar, Ce H₁₂O, which occurs in two modifications, called dextro-glucose, or dextrose, and levo-glucose, (also called Levulose), according as it turns the plane of polarization to the right or left. A solution of cane-sugar warmed with dilute acids, or left in contact with yeast, is converted into dextrose and levulose, C12H22O11+ H2O=C6H12O6 + C6H12O6. These modifications can be separated, thus-10 parts of the mixture of sugar are dissolved in 100 parts of water, and cooled with ice; then six parts of powdered calcium hydrate are added, the calcium compound of levulose is precipitated and separated from the soluble calcium compound of dextrose by strong pressure, washed, ed, and decomposed by carbonic-acid gas. The term "glucose" is generally applied to a mixture composed of dextro-glucose, maltose, dextrin and water prep prepared from corn starch, by heating with dilute acids. It is widely used in the manufacture of candy, and was formerly an important commodity in the brewing of malt liquors.
Aiton's Encyclopedia (1910)
glu'kos, the chemical name of several sugars, less sweet than cane sugar. Commercially speaking, glucose is a sirup, lacking in sweetness, produced by the action of sulphuric acid on the starch of grain or potatoes. Glucose is the base of most cheap sirups. It is not poisonous nor in any way unwholesome. The chief prejudice against glucose arises from its extensive use as an adulterant or substitute for the higher priced maple, cane, and beet products. Glucose is distributed widely in nature. It is a constituent of grapes, cherries, plums, figs, and many other sweet fruits. The sugary sweet excretion on raisins is glucose. It is a constituent of honey. It occurs also in living animal tissues, and in the intestine, hepatic veins, and liver tissue of human beings. In the disease known as diabetes it exists in large quantities in the urine, and may be found in all fluids of the body. See Sugar
What Has Changed in the Last Century
Collier's called levulose "levo-glucose," as though it were simply glucose twisted the other way; chemists now class fructose as a structurally different sugar (a ketose, not an aldose), and the mirror-image L-glucose is a laboratory curiosity that the body cannot use. The biggest shift is medical: Aiton's 1910 note that glucose "exists in large quantities in the urine" in diabetes was a diagnostic observation with no remedy, and in 1921 insulin was isolated in Toronto by Banting and Best, turning a fatal disease into a managed one. Blood glucose is now measured at home with enzyme test strips and continuous sensors, and glucose metabolism was mapped in detail through the 1930s. Corn syrup, which Aiton defended as "not poisonous nor in any way unwholesome," is still cheap and ubiquitous, but since the 1970s much of it is enzymatically converted to high-fructose corn syrup, and health bodies now urge limits on added sugars of all kinds.
Written for this edition, 2026.