constants of cellulose sulphocarbonate (solution)._--In
investigations of the solutions we make use of various analytical
methods, which may be briefly described, noting any results bearing upon
special points.

_Total alkali._--This constant is determined by titration in the usual
way. The cellulose ratio, C_{6}H_{10}O_{5} : 2NaOH, is within the
ordinary error of observation, 2 : 1 by weight. A determination of alkali
therefore determines the percentage of cellulose.

_Cellulose_ may be regenerated in various ways--viz. by the action of
heat, of acids, of various oxidising compounds. It is purified for
weighing by boiling in neutral sulphite of soda (2 p.ct. solution) to
remove sulphur, and in very dilute acids (0.33 p.ct. HCl) to decompose
residues of 'organic' sulphur compounds. It may also be treated with
dilute oxidants. After weighing it may be ignited to determine residual
inorganic compounds.

_Sulphur._--It has been proved by Lindemann and Motten [Bull. Acad. R.
Belg. (3), 23, 827] that the sulphur of sulphocarbonates (as well as of
sulphocyanides) is fully oxidised (to SO_{3}) by the hypochlorites
(solutions at ordinary temperatures). The method may be adapted as
required for any form of the products or by-products of the viscose
reaction to be analysed for _total sulphur_.

The sulphur present in the form of dithiocarbonates, including the
typical cellulose xanthogenic acid, is approximately isolated and
determined as CS_{2} by adding a zinc salt in excess, and distilling off
the carbon disulphide from a water bath. From freshly prepared solutions
a large proportion of the disulphide originally interacting with the
alkali and cellulose is recovered, the result establishing the general
conformity of the reaction to that typical of the alcohols. On keeping
the solutions there is a progressive interaction of the bisulphide and
alkali, with formation of trithiocarbonates and various sulphides. In
decomposing these products by acid reagents hydrogen sulphide and free
sulphur are formed, the estimation of which presents no special
difficulties.

In the spontaneous decomposition of the solution a large proportion of
the sulphur resumes the form of the volatile disulphide. This is
approximately measured by the loss in total sulphur in the following
series of determinations, in which a viscose of 8.5 p.ct. strength
(cellulose) was dried down as a thin film upon glass plates, and
afterwards analysed:

(a) Propo