NOTES AND ABSTRACTS IN CHEMISTRY AND PHARMACY. 233 
tr 
after it is washed and dried, constitutes pure acetic cellulose. Its composi¬ 
tion is as follows :— 
C 6 H 7 (C 2 H s O) 3 O s . 
It is cellulose, therefore, in which three atoms of hydrogen have been replaced 
by acetyle. This body is insoluble in water, alcohol, ether, and benzol; 
soluble in glacial acetic acid and in oil of vitriol. When boiled with dilute 
alkalies, cellulose is regenerated and an acetate formed. 
If a smaller proportion of acetic anhydride be employed, and the mixture 
subjected to a lower temperature, the cotton swells without dissolving, and 
derivatives containing only one or two atoms of acetyle (mono- or di-acetic 
cellulose) are obtained, which, however, cannot be purified on account of 
their insolubility. 
The facility with which anhydrous acetic acid attacks starch varies much 
with the state of aggregation of this substance, and the proportion and purity 
of the anhydride. When the temperature does not exceed 140° F. the starch 
swells a great deal without dissolving. After washing a white amorphous 
substance is obtained, insoluble in water, alcohol, ether, and glacial acetic 
acid. It is not rendered blue by iodine, but is saponified by caustic alkalies 
with regeneration of the insoluble starchy matter, which then becomes blue 
with iodine. This substance is triacetic-starch. 
Cr,H 7 (CoH 3 0) 3 0 5 . 
If the temperature exceeds 150° F. the swollen mass dissolves, forming an 
amber syrup, from which water precipitates a white amorphous substance in¬ 
soluble in water, alcohol, and ether, but soluble in glacial acetic acid. This 
substance is rapidly decomposed by dilute caustic alkalies, but forms a solu¬ 
tion which, when carefully neutralized, is rendered blue by iodine, and from 
which alcohol precipitates a substance identical with ordinary soluble starch. 
There is, therefore, a triacetic derivative of soluble and also of insoluble 
starch, both having the same composition. By employing a still higher tem¬ 
perature for the reaction a derivative is obtained also triacetic, but from 
which alkalies regenerate dextrine instead of starch. 
Glycogen heated to 155° with acetic anhydride furnishes an insoluble pro¬ 
duct, which is also a triacetic body :—■ 
C 6 H 7 (C 2 H 3 0) 3 0 s . 
Gum arabic, finely powdered and heated to 150° with 2 parts of acetic an¬ 
hydride, swells without dissolving, and yields an insoluble white powder, 
having the composition of diacetic-arabin :— 
CoH s (C 2 H 3 0) 2 0 5 . 
By employing an excess of the anhydride and a temperature of 180°, a body 
is obtained presenting similar characters, but having the composition of two 
molecules of arabin, in which 5 atoms of hydrogen are replaced by 5 of 
acetyle:— 
c 12 h 15 (c 2 h 3 o) 6 o 10 .; 
On account of this latter reaction, M. Schurtzenberger is inclined to double 
the formula for arabin. He regards cellulose, starch, dextrine, and glycogen 
as isomeric triatomic alcohols, according to the formula— 
CgHyOo ) Q 
H 3 \ °3 
And considers the result of his researches as confirmatory of that view. 
VOL. XI. 
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