pound, there
occurs a continual aggregation of the cellulose with dissociation of the
alkali and CS residues and it has been found impossible to assign a
limit to the dissociation, i.e. to fix a point at which the transition
from soluble sulphocarbonate to insoluble cellulose takes place.

On these grounds it will be seen we are reduced to a somewhat
speculative treatment of the hypothetical ultimate unit group, which is
taken as of C_{6} dimensions.

As there has been no addition of experimental facts directly
contributing to the solution of the problem, the material available for
a discussion of the probabilities remains very much as stated in the
first edition, pp. 75-77. It is now generally admitted that the
tetracetate _n_ [C_{6}H_{6}O.(OAc)_{4}] is a normal cellulose ester;
therefore that four of the five O atoms are hydroxylic. The fifth is
undoubtedly carbonyl oxygen. The reactions of cellulose certainly
indicate that the CO- group is ketonic rather than aldehydic. Even when
attacked by strong sulphuric acid the resolution proceeds some
considerable way before products are obtained reducing Fehling's
solution. This is not easily reconcilable with any polyaldose formula.
Nor is the resistance of cellulose to very severe alkaline treatments.
The probability may be noted here that under the action of the alkaline
hydrates there occurs a change of configuration. Lobry de Bruyn's
researches on the change of position of the typical CO- group of the
simple hexoses, in presence of alkalis, point very definitely in this
direction. It is probable that in the formation of alkali cellulose
there is a constitutional change of the cellulose, which may in effect
be due to a migration of a CO- position within the unit group. Again
also we have the interesting fact that structural changes accompany the
chemical reaction. It is surprising that there should have been no
investigation of these changes of external form and structure, otherwise
than as mass effects. We cannot, therefore, say what may be the
molecular interpretation of these effects. It has not yet been
determined whether there are any intrinsic volume changes in the
cellulose substance itself: and as regards what changes are determined
in the reacting unit or molecule, we can only note a fruitful subject
for future investigation. _A priori_ our views of the probable changes
depend upon the assumed constitution of the unit group. If of the
ordinary carbohydrate type