reactions, and are not homogeneous. They
yield on boiling with condensing acids from 6 to 9 p.ct. furfural. It is
usual to regard furfural as invariably produced from a pentose residue.
But this interpretation ignores a number of other probable sources of
the aldehyde. It must be particularly remembered that laevulose is
readily condensed (a) to a methylhydroxyfurfural

C_{6}H_{1}O_{6} - 3H_{2}O = C_{6}H_{6}O_{3} = C_{5}(OH).H_{2}.(CH_{3})O_{2}

and (b) by HBr, with further loss of OH, as under:

C_{6}H_{12}O_{6} - 4H_{2}O + HBr = C_{5}H_{3}(CH_{2}Br)O

and generally the ketoses are distinguished from the aldoses by their
susceptibility to condensation. Such condensation of laevulose has been
effected by two methods: (a) by heating the concentrated aqueous
solution with a small proportion of oxalic acid at 3 atm. pressure
[Kiermayer, Chem. Ztg. 19, 100]; (b) by the action of hydrobromic acid
(gas) in presence of anhydrous ether; the actual compound obtained being
the omega-brommethyl derivative [Fenton, J. Chem. Soc. 1899, 423].

This latter method is being extended to the investigation of typical
celluloses, and the results appear to confirm the view that cellulose
may be of ketonic constitution.

The evidence which is obtainable from the synthetical side of the
question rests of course mainly upon the physiological basis. There are
two points which may be noted. Since the researches of Brown and Morris
(J. Chem. Soc. 1893, 604) have altered our views of the relationships of
starch and cane sugar to the assimilation process, and have placed the
latter in the position of a primary product with starch as a species of
overflow and reserve product, it appears that laevulose must play an
important part in the elaboration of cellulose. Moreover, A. J. Brown,
in studying the cellulosic cell-collecting envelope produced by the
_Bacterium xylinum_, found that the proportion of this product to the
carbohydrate disappearing under the action of the ferment was highest in
the case of laevulose. These facts being also taken into consideration
there is a concurrence of suggestion that the typical CO group in the
celluloses is of ketonic character. That the typical cotton cellulose
breaks down finally under the action of sulphuric acid to dextrose
cannot be held to prove the aldehydic position of the carbonyls in the
unit groups of the actual cellulose molecule or aggregate.

We again are confronted with the problem of the aggr