60.8

Dibenzoate C 63.10 64.86}
H 3.40 4.86} 65.5 66.6 34.3 40.3

The divergence of the numbers, especially for the dibenzoate, in the
case of the hydrogen, and yield of cellulose on hydrolysis are
noteworthy. They confirm the probability of the occurrence of secondary
changes in the ester reactions.

_Action of nitrating acid upon the benzoates._--From the benzoates above
described, mixed nitro-nitric esters are obtained by the action of the
mixture of nitric and sulphuric acids. The residual OH groups of the
cellulose are esterified and substitution by an NO_{2} group takes place
in the aromatic residue, giving a mixed nitric nitrobenzoic ester. The
analysis of the products points to the entrance of 1 NO_{2} group in the
benzoyl residue in either case; in the cellulose residue 1 OH readily
reacts. Higher degrees of nitration are attained by the process of
solution in concentrated nitric acid and precipitation by pouring into
sulphuric acid. In describing these mixed esters we shall find it
necessary to adopt the C_{12} unit formula.

In analysing these products we have employed the Dumas method for _total
nitrogen_. For the O.NO_{2} groups we have found the nitrometer and the
Schloesing methods to give concordant results. For the NO_{2} groups it
was thought that Limpricht's method, based upon reduction with stannous
chloride in acid solution (HCl), would be available. The quantitative
results, however, were only approximate, owing to the difficulty of
confining the reduction to the NO_{2} groups of the nitrobenzoyl
residue. By reduction with ammonium sulphide the O.NO_{2} groups were
entirely removed as in the case of the cellulose nitrates; the NO_{2}
was reduced to NH_{2} and there resulted a cellulose amidobenzoate,
which was diazotised and combined with amines and phenols to form yellow
and red colouring matters, the reacting residue remaining more or less
firmly combined with the cellulose.

_Cellulose dinitrate-dinitrobenzoate, and cellulose
trinitrate-dinitrobenzoate._--On treating the fibrous benzoate--which is
a dibenzoate on the C_{12} basis--with the acid mixture under the usual
conditions, a yellowish product is obtained, with a yield of 140-142
p.ct. The nitrobenzoate is insoluble in ether alcohol, but is soluble in
acetone, acetic acid, and nitrobenzene. In purifying the product the
former solvent is used to remove any cellulose nitrates. To obtain the