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LAEVULOSE See also: SUGAR, a See also: carbohydrate of the See also: formula CsH12O6
.
It is closely related to ordinary d-See also: glucose, with which it occurs in many fruits, starches and also in honey
.
It is a hydrolytic product of inulin, from which it may be prepared; but it is more usual to obtain it from " invert sugar," the mixture obtained by hydrolysing See also: cane sugar with sulphuric acid
.
Cane sugar then yields a syrupy mixture of glucose and See also: fructose, which, having been freed from the acid and concentrated, is mixed with See also: water, cooled in ice and calcium hydroxide added
.
The fructose is precipitated as a saccharate, which is filtered, suspended in water and decomposed by See also: carbon dioxide
.
The liquid is filtered, the filtrate concentrated, and the syrup so obtained washed with cold See also: alcohol
.
On cooling the fructose separates
.
It may be obtained as a syrup, as See also: fine, silky needles, a See also: white crystalline powder, or as a granular crystalline, somewhat hygroscopic mass
.
When anhydrous it melts at about 95° C
.
It is readily soluble in water and in dilute alcohol, but insoluble in absolute alcohol
.
It is sweeter than cane sugar and is more easily assimilated
.
It has been employed under the name diabetin as a sweetening
See also: agent for diabetics, since it does not increase the sugar-content of the urine; other medicinal applications are in See also: phthisis (mixed with See also: quassia or other bitter), and for See also: children suffering from See also: tuberculosis or scrofula in place of cane sugar or milk-sugar
.
Chemically, fructose is an oxyketone or ketose, its structural formula being CH2OH•(CH•OH)m.CO•CH2OH; this result followed from its conversion by H . Kiliani into methylbutylacetic acid . TheSee also: form described above is laevo-rotatory, but it is termed d-fructose, since it is related to d-glucose
.
Solutions exhibit mutarotation, fresh solutions having a specific rotation of -104.0°, which gradually diminishes to — 92°
.
It was synthesized by Emil Fischer, who found the synthetic sugar which he named a-acrose to be (d+l)-fructose, and by splitting this mixture he obtained both the d and 1 forms
.
Fructose resembles d-glucose in being fermentable by yeast (it is the one ketose which exhibits this See also: property), and also in its power of reducing alkaline copper and See also: silver solutions; this latter property is assigned to the readiness with which hydroxyl and ketone See also: groups in close proximity suffer oxidation
.
For the structural (stereochemical) relations of fructose see SUGAR
.
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[back] JAMES ANTHONY FROUDE (1818-1894) |
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