, formulated with an open chain, there is
little to surmise beyond the change of position of a CO- group. But
alternative formulae have been proposed. Thus the tetracetate is a
derivative to be reckoned with in the problem. It is formed under
conditions which preclude constitutional changes within the unit groups.
The temperature of the main reaction is 30 deg.-40 deg., the reagents are used
but little in excess of the quantitative proportions, and the yields are
approximately quantitative. If now the derivative is formed entirely
without the hydrolysis the empirical formula C_{6}H_{6}O.(OAc)_{4}
justifies a closed-ring formula for the original viz.
CO<[CHOH]_{4}>CH_{2}; and the preference for this formula depends upon
the explanation it affords of the aggregation of the groups by way of
CO-CH_{2} synthesis.

The exact relationship of the tetracetate to the original cellulose is
somewhat difficult to determine. The starting-point is a cellulose
hydrate, since it is the product obtained by decomposition of the
sulphocarbonate. The degree of _hydrolysis_ attending the cycle of
reactions is indicated by the formula 4 C_{6}H_{10}O_{5}.H_{2}O. It has
been already shown that this degree of hydrolysis does not produce
molecular disaggregation. If this hydrate survived the acetylation it
would of course affect the empirical composition, i.e. chiefly the
carbon percentage, of the product. It may be here pointed out that the
extreme variation of the carbon in this group of carbohydrate esters is
as between C_{14}H_{20}O_{10} (C = 48.3 p.ct.) and C_{14}H_{18}O_{9} (C
= 50.8 p.ct.) i.e. a tetracetate of C_{6}H_{12}O_{6} and
C_{6}H_{10}O_{5} respectively. In the fractional intermediate terms it
is clear that we come within the range of ordinary experimental errors,
and to solve this critical point by way of ultimate analysis must
involve an extended series of analyses with precautions for specially
minimising and quantifying the error. The determination of the acetyl by
saponification is also subject to an error sufficiently large to
preclude the results being applied to solve the point. While, therefore,
we must defer the final statement as to whether the tetracetate is
produced from or contains a partly hydrolysed cellulose molecule, it is
clear that at least a large proportion of the unit groups must be
acetylated in the proportion C_{6}H_{6}O.(OAc)_{4}.

It has been shown that by the method of Franchimont a higher proportion
o