f acetyl groups can be introduced; but this result involves a
destructive hydrolysis of the cellulose: the acetates are not
derivatives of cellulose, but of products of hydrolytic decomposition.

It appears, therefore, that with the normal limit of acetylation at the
tetracetate the aggregation of the unit groups must depend upon the CO-
groups and a ring formula of the general form CO<[CHOH]_{4}>CH_{2} is
consistent with the facts.

Vignon has proposed for cellulose the constitutional formula

O------CH
| | \
| O \[CHOH]_{3}
| | /
CH_{2}-CH/

with reference to the highest nitrate, and the decomposition of the
nitrate by alkalis with formation of hydroxypyruvic acid. While these
reactions afford no very sure ground for deductions as to constitutional
relationships, it certainly appears that, if the aldose view of the unit
group is to be retained, this form of the anhydride contains suggestions
of the general tendency of the celluloses on treatment with condensing
acids to split off formic acid in relatively large quantity [Ber. 1895,
1940]; the condensation of the oxycelluloses to furfural; the
non-formation of the normal hydroxy-dicarboxylic acids by nitric acid
oxidations. Indirectly we may point out that any hypothesis which
retains the polyaldose view of cellulose, and so fails to differentiate
its constitution from that of starch, has little promise of progress.
The above formula, moreover, concerns the assumed unit group, with no
suggestion as to the mode of aggregation in the cellulose complex. Also
there is no suggestion as to how far the formula is applicable to the
celluloses considered as a group. In extending this view to the
oxycelluloses, Vignon introduces the derived oxidised group

CHO.(CHOH)_{3}.CH . CO
|_O__|

--of which one is apportioned to three or four groups of the cellulose
previously formulated: these groups in condensed union together
constitute an oxycellulose.

These views are in agreement with the experimental results obtained by
Faber and Tollens (p. 71). They regard the oxycelluloses as compounds of
'celloxin' C_{6}H_8{O}_{6} with 1-4 mols. unaltered cellulose; and the
former they particularly refer to as a lactone of glycuronic acid. But
on boiling with lime they obtain dioxybutyric and isosaccharinic acids;
both of which are not very obviously related to the compounds formulated
by Vignon. We revert with prefer