Researches on Cellulose | Page 7

upon the
former that their rigidity and resistance to water are in no way affected
by cultivation in a silica-free medium. In other words, the structural
peculiarities of the gramineæ in these respects are due to the physical
characteristics chiefly of the (lignified) cells of the hypodermal tissue,
and to the composition and arrangement of the cells of the cuticle.
'Swedish' filter papers of modern make are so far freed from inorganic
constituents that the weight of the ash may be neglected in nearly all
quantitative experiments [Fresenius, Ztschr. Anal Chem. 1883, 241]. It
represents usually about 1/1000 mgr. per 1 sq. cm. of area of the
paper.
The form of an 'ash' derived from a fibrous structure, is that of the
'organic' original, more or less, according to its proportion and
composition. The proportion of 'natural ash' is seldom large enough,
nor are the components of such character as to give a coherent ash, but
if in the case of a fibrous structure it is combined or intimately mixed
with inorganic compounds deposited within the fibres from solution,
the latter may be made to yield a perfect skeleton of the fibre after
burning off the organic matter. It is by such means that the mantles
used in the Welsbach system of incandescent lighting are prepared. A
purified cotton fabric--or yarn--is treated with a concentrated solution
of the mixed nitrates of thorium and cerium, and, after drying, the
cellulose is burned away. A perfect and coherent skeleton of the fabric
is obtained, composed of the mixed oxides. Such mantles have fulfilled
the requirements of the industry up to the present time, but later
experiments forecast a notable improvement. It has been found that
artificial cellulose fibres can be spun with solutions containing
considerable proportions of soluble compounds of these oxides. Such
fibres, when knitted into mantles and ignited, yield an inorganic
skeleton of the oxides of homogeneous structure and smooth contour.
De Mare in 1894, and Knofler in 1895, patented methods of preparing

such cellulose threads containing the salts of thorium and cerium, by
spinning a collodion containing the latter in solution. When finally
ignited, after being brought into the suitable mantle form, there results
a structure which proves vastly more durable than the original
Welsbach mantle. The cause of the superiority is thus set forth by V. H.
Lewes in a recent publication (J. Soc. of Arts, 1900, p. 858): 'The
alteration in physical structure has a most extraordinary effect upon
the light-giving life of the mantle, and also on its strength, as after
burning for a few hundred hours the constant bombardment of the
mantle by dust particles drawn up by the rush of air in the chimney
causes the formation of silicates on the surface of the mantle owing to
silica being present in the air, and this seems to affect the Welsbach
structure far more than it does the "Clamond" type, with the result that
when burned continuously the Welsbach mantle falls to so low a pitch
of light emissivity after 500 to 600 hours, as to be a mere shadow of its
former self, giving not more than one-third of its original light, whilst
the Knofler mantle keeps up its light-emitting power to a much greater
extent, and the Lehner fabric is the most remarkable of all. Two Lehner
mantles which have now been burning continuously in my laboratory
for over 3,000 hours give at this moment a brighter light emissivity
than most of the Welsbachs do in their prime.' ...'The new developments
of the Clamond process form as important a step in the history of
incandescent gas lighting as the discoveries which gave rise to the
original mantles.'
It has further been found that the oxides themselves can be dissolved in
the cellulose alkaline sulphocarbonate (viscose) solution, and artificial
threads have been spun containing from 25 to 30 p.ct. of the oxides in
homogeneous admixture with the cellulose. This method has obvious
advantages over the collodion method both in regard to the molecular
relationship of the oxides to the cellulose and to cheapness of
production.
UNTERSUCHUNGEN ÜBER VERSCHIEDENE
BESTIMMUNGSMETHODEN DER CELLULOSE.
H. SURINGAR AND B. TOLLENS (Ztschr. angew. Chem. 1896, No.

23).
~INVESTIGATION OF METHODS OF DETERMINING
CELLULOSE.~
Introduction.--This is an exhaustive bibliography of the subject,
describing also the various methods of cellulose estimation, noted in
historical sequence. First, the Weende 'crude fibre' method (Henneberg)
with modifications of Wattenberg, Holdefleiss, and others is dealt with.
The product of this treatment, viz. 'crude fibre' is a mixture, containing
furfuroids and lignone compounds. Next follows a group of processes
which aim at producing a 'pure cellulose' by eliminating lignone
constituents, for which the merely hydrolytic treatments of the Weende
method are ineffectual. The method of F. Schulze--prolonged digestion
with dilute nitric acid, with addition of chlorate--has been largely