ne complex.

Nor is there any satisfactory application of this by-product as yet
evolved. Evaporation and combustion involve large losses of sulphur
[D.R.P. 74,030, 83,438; Seidel and Hanak, Mitt. Techn. Gew. Mus. 1898].
A more complete regeneration of the sulphur has been the subject of a
series of patents [D.R.P. 40,308, 69,892, 71,942, 78,306, 81,338], but
the processes are inefficient through neglect of the actual state of
combination of the S, viz. as an organic sulphonate. The process of V.B.
Drewson (D.R.P. 67,889) consists in heating with lime under pressure,
yielding calcium monosulphite (with sulphate and the lignone complex in
insoluble form). The sulphite is redissolved as bisulphite by treatment
with sulphurous acid. This process is relatively costly, and yields
necessarily an impure lye. It has been proposed to employ the product as
a foodstuff both in its original form and in the form of benzoate
(D.R.P. 97,935); but its unsuitability is obvious from its composition.
A method of destructive distillation has been patented (D.R.P. 45,951).
The author has investigated the process, and finds that the yield of
useful products is much too low for its economical development. Fusion
with alkaline hydrates for the production of oxalic acid (D.R.P. 52,491)
is also excluded by the low yield of the product.

The application of the liquor for tanning purposes (D.R.P. 72,161)
appears promising from the fact that 28 p.ct. of the dry residue is
removed by digestion with hide powder. This application has been
extensively investigated, but without practical success. Various
probable uses are suggested by the viscosity of the evaporated extract.
As a substitute for glue in joinery work, bookbinding, &c., it has
proved of little value. It is applied to some extent as a binding
material in the manufacture of briquettes, also as a substitute for
gelatin in the petroleum industry. Cross and Bevan (E.P. 1548/1883) and
Mitscherlich (D.R.P. 93,944 and 93,945) precipitate a compound of the
lignone complex and gelatin by adding a solution of the latter to the
liquors. The compound is redissolved in weak alkaline solutions and
employed in this form for engine-sizing papers. Ekman has patented a
process (D.R.P. 81,643) for 'salting out' the lignone sulphonates, the
product being resoluble in water and the solution having some of the
properties of a solution of dextrin. Owing to its active chemical
properties this product--'dextron'--