liquid to cellulose and
duration of digestion. Each of these was varied in definite gradations,
and the effect measured. The degree of action was measured in terms of
'reducing sugar,' calculated from the results of estimation by Fehling
solution, as 'glucose' per cent. of original cellulose (or wood).

(a) _Cellulose._ [Wood-cellulose obtained by bisulphite
process.]--With a proportion of total liquid to cellulose of 27 : 1, and
using sulphuric acid as the hydrolysing agent, the optimum results were
obtained with acids of 0.45-0.60 p.ct. (H_{2}SO_{4}) and pressures of
6-8 atm. The maximum yield of 'sugar' was 45 p.ct. of the cellulose.

Under the above conditions the maximum of conversion is attained in 2
hours.

Having now regard to the production of a solution of maximum
_concentration_ of dissolved solids, the following conditions were
asertained to fulfil the requirement, and, in fact, may be regarded as
the economic optimum:

Proportion of total liquid 6 times wt. of cellulose
Concentration of acid 0.5 p.ct. H_{2}SO_{4}
Pressure 10 atm.
Duration of digestion 1.5 hour

giving a yield of 41 p.ct. 'reducing sugar' calculated to the original
cellulose (dry).

_Alcoholic Fermentation of Neutralised Extract._--The liquors were found
to ferment freely, and on distillation to yield a quantity of alcohol
equal to 70 p.ct. of the theoretical--i.e. on the basis of the numbers
for copper oxide reduction.

(b) _Hydrolytic 'Conversion' of Wood (Lignocellulose)._--A similarly
systematic investigation carried out upon pine sawdust established the
following as optimum conditions:

Proportion of total liquid 5 times wt. of wood
Concentration of acid 0.5 p.ct. H_{2}SO_{4}
Pressure 9 atm.
Duration of digestion 15 minutes

giving a yield of 20 p.ct. 'reducing sugar,' calculated from the
'Fehling' test.

_Fermentation_ of the neutralised extracts gave variable results. The
highest yields obtained were 60 p.ct. of theoretical, the author finally
concluding that under properly controlled conditions of inversion and
fermentation 100 kg. wood yield 6.5 l. absolute alcohol.

UeBER DIE URSACHE DER VON SIMONSEN BEOBACHTETEN UNVOLLSTAeNDIGKEIT DER
VERGAeHRUNG DER AUS HOLZ BEREITETEN ZUCKERFLUeSSIGKEITEN.

B. TOLLENS (Ztschr. angew. Chem., 1898, 15).

~ON THE CAUSE OF INCOMPLETE FERMENTATION OF SUGARS OBTAINED BY ACID
HYDR