U. S . Department of Agriculture, Forest Service
a
FOREST PRODUCTS LABORATOR Y
In cooperation with the University of Wisconsi n
MADISON, WISCONSI N
ci
EFFECT OF PARTIAL HYDROLYSIS ON THE
ALKALI SOLUBILITY OF WOO D
By
L . F . Hawley, Principal Chemis t
and
W . G. Campbell, Commonwealth Fund Fello w
Published i n
Industrial & Engineering Chemistry
June, 1927
4.3 /// /
test was Sitka spruce '
tts composition and it s
tment were first determi :
tained with hydrolyze d
~e .
god is given i n
coy+•osition of th e
er cent caustic sod a
erature .
Table I .--Analysis of o',iz'tnal wood
(Results on basis of Weight of origina l , dry wood )
per,c4nt
Water soluble . ,i
Ether soluble
Alkali soluble
Cellulose
Lignin
M ethoxyl
Total pentosans Pentosans not in cellulose
4i8
114 .
4. 1
.7
12 . 0
62 . 5
29 . 3
4. 8
9.9
6. 2
Table II .--Analysis of wood residue after treatmen t
with 1 per cent NaOH for 1 hour a t
100° C .
(Results on basis of weight of original dry wood )
Per cen t
Loss on alkali treatment 13 . 7
Cellulose
Lignin
Methoxyl
Total pentosans
Pentosans not in cellulose
59 . 2
27 . 7
4. 3
7. 4
3 .9
tables t
nalysi so
det e
se a n
pentosan s
ical dat
th e
Forme
ter
Experimental
In studying the alkali solubility of the hydrolyze d
wood, the general plan was to subject samples to differen t
degrees of hydrolysis, analyze them, treat them with causti c
soda, and analyze the residue . It has frequently been found ,
however, that on account of the difficulty of obtaining th e
same , conditions throughout the mass, a chemical reactio n
which takes place with small quantities of wood, such as
the sample for analysis, can not be reproduced exactly whe n
larger quantities are used . For this reason it was no t
attempted to hydrolyze enough wood so that the residue woul d
ent for an analysis, alkali treatment, and th e
alysis of the resid . Instead, two samples wer e
under as nearl a_sossible the same conditions ,
lysis and th e
rmORe analyse s
eight on hydrol tables show s
is obtained b y
ose, 1~, and .. pent :
cellulermine d
from tIa ~ JOiilyses of the origi rate wood (Tae, .
a 1 of the
n s
'e
r hydrolysis,, to whin'h is also owed th wate r
solu
in the original wood, on the assump+% ion that this i s
all 16lbved by hydrolysise It is immediately noticeabl e
'hat the calculated loss is always considerably higher than
. *hat actually determined . This difference can be explained
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only i0e 1
partl ;
tip .
co ~.
wood whic h • .
yz .
0 Tip►' ,
feoex-- vain
uents'
the ' ~
:1 03A.
the Wrtlti
ti _
•le ': II :
cent of tio'
imply
lose, lignin, o pe
slioul4 ada u,p
.1- the partly h
wood totals wte
140 TAP vrWt a
yzed samples to considerably less than i . ■ per cent, th e
is good reason to 'assume the presende of Some material i ' . ~ .
the . laistwhich was not present in the or j,gi r
ands
ev
does not show in any of the determination .
it is la, 1ge .ly gOit;MO
esubtanc,hrievdta
the alkali treatment, in t,?aat. the sums of .the - htft •
!
constituents de-t,erlmL'ned on 'a aa. al•i=,tr-e.stdiv~ - ~d
all come very c'1oar to 100- P g-r Bent of the. aeto _iveiglt o f
residue, the extreme variati me being betwe'en 04.0 ad 100 . 5
per cent .
r
ence s
',!,he figures 'in Table III, aside from the di
between determined and calculated. losses, give little infort_
mation that has , wt been available previously . Thg., s
effect of hydrolysis on th-e amount of lin and , , ~
and the continuous but not complete rye ,al of tii p1G.f>> an s
a
.: - s
have been shown in pa ge-vious wok .
This . set effurnished mainly for compar isom with $Ole IV in $4*r t o
show the qus.ntit g 41we effect of the a1 1i treatmem 4
Table IV gives '*e loss in weight of- t duplicate saris le s
on hydrolyai s, heir laD+ g-s in weight ''x- a:1-ali treatment , an d
then the analysis of th'e residues afitOT t g Mcal i treatment .
The alkali-treatment ms identical wit .4 .ttl t. , ed ii b
analytical de'te- izii a,' .Nmn of the alkali-MI-kW a ~? s? ., Hof th e
original wood -saea
4 ; 4.weatment with I per
hydroxide at boili water temperature for 1 Sour .
Despite the small differenees in the loss on .{hydro l
ysis between the second -column_ of T :'tLe IV aid the secon d
column of Table III, some eonclua,i:ons may say be
vn
from a comparison of the analytical d6ke rni,m,a .ons a t.
stand .
It will be noti'ced -that in every c ape 'td
o weight due to the alkali treatment is r a OP gf
in
each of the constituen - -,=
mined, axed .:toms is als*
e
the orig . ., A. -wmo d
I
ev :
"W
I.
' r Ij ~
1 -.
-C•
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=P "
t
err
if• j if
.
'y
J• i
_ - -
1 '
. .
yy
r' ~-" ` !~ ~ :~~
1,
;L .' ,
ij.~
each constituent is less in Table IV than in the corresponding part of Table XII . There is always a decrease in th e
constituents shown in Table IV as the severity of the hydrolysis increases, with the exception that the lignin during th e
first three hydrolyses remains practically constant .
The largest variations between the two tables,however, are in the cellulose . Comparing the sixth column o f
Table IV with the fourth of Table III, it is seen that th e
alkali solubility of the cellulose becomes very high afte r
the last four hydrolyses, although there is no orderly in crease in the alkali solubility with increasing severity o f
hydrolysis . The lignin, on the other hand, is rendered onl y
slightly solid Z by the hydrolysis, and even after the mos t
drastic'treatment, with 15 per cent hydrochloric acid, onl y
3 per cent out of the 26 per cent present after hydrolysi s
is removed by the subsequent alkali treatment .
The methoxyl is removed by the alkali treatment i n
increasing amounts as the hydrolysis progresses . Although
after the first three hydrolyses the amount of methoxyl de creases while the lignin determination remains stationary ,
this fact should not be considered an indication that the
methoxyl was not a part of the original lignin, since th e
chemical method by which the lignin was isolated has bee n
shown to Fesult in the loss of a considerable portion of th e
methox 1 - _an d_ it is in this relatively unstable portion tha t
~y e p
hoxyl . loss
on alkali
treatment may be suppose d
: • - O
' . }i . ". 1 '
„'I
f occu
-a
.1 f
whit
out great inse, lignin ,
le -effect on th e
5 per cent pentosans in the h
_ ., _
ecre a
e nt
by the alkali treatment, although in the origin .
ood pentosans to the amount of 7 .4 per cent were insolubleal i
(Table II) . This high alkali solubility of the p
s in
the partly hydrolyzed wood was progressive as hy d
became ire severe .
*I''
x'
•
r-
e
gr = -= AL, in;
is no
abl '
ver
lubilit
onst i
A,
'b¢ OttOMAIW94 tom'= alk 'Itolubility, Table I I
to ttrQ
c pn
. 0 ' Z.
otter one' eofis'tx
t with
eel
nex
soluble) . In partly hydrolyzed wood the most soluble constituent at all stages of hydrolysis is the cellulose, th e
loss in cellulose reaching 12 .8 per cent in two cases . Th e
li t in, on the contrary, is very little affected by th e
olysis, the lignin of the original wood being almost a s
e in alkali as the lignin in the hydrolyzed residues .
r-~x
- r- : .
V
- ;7 = ~I ''"
}r Remark s
.
V_I II :'
r
~
rp
44:
F
rY ~
,
~I
i
y
or qv
st
f v
.
-Ir
•
r .7;
r~,
C .
er ex`:
hat
di►t
Irs
los e
as e
avail !•l e
ood
e partly decaye d
I
thQ
s of
te,
:I
Iff
~~
ay . p
l
I __
fr Pillrl~
•• }' . I
acto condi t
• c_ '
At pape r
p,
pro
en . ac = d, shows an :
;mina ,
•; although it is quit e
can no manufacture lign i
d pulp .- Another instanc e
ht be made from comparativ e
nd in the pulping of woo d
r
i
cellulose
Hawley and Wise, op . cit ., p . 259 .
%Ming and Statdl, '4r •
Jl. .• ,
-8♦1 '
4
snc e ,
w .
s
-ete"rmined a s
e analytical re- '
ial might not have '
ic .. } ata on th.'
1 w. od
A
ed .
d
ct o
is o
ans, .
tires .+I
n w
Qf .
'
ids "
rmi
S ±forde d
on .
.
'•-' '
•'t,
o
Sum
ma Mary
,
.
,
Although- f ft in-nt.
Wf,emt
4** on wood,
so far . as removal of cm,st4tuents is
apparentl y
the same as a hydei*ysi6, yet these two ptoeeb6 .a differ i n
their effecIt on the alkali solubility of the resi0e .
2. The total alkali solubility of paVtIV decaye d
wood is much greater than that of wood whioh has been hydrolyzed to thel same extent (as shown by equal lmssA41 weight) .
3. The solubility of the lrn :n: alkali is ver y
slightly increased by partial hydVolyas-, wa$sZeaq; decay ma y
render the lignin 50 per cent soluble .
4. The solubility of the .reRid4al cellw1o6e i, =considerably increased by partial hydrOlyeia l but prObably root
to the same extent as it is by decay .
5. There is .in partially hydrolyzed wood ,s ), terialvprobably a degraaation product of the cellulose, whiff
not
determined as cellaose, -Iignin, or pentosans . Thi s
is soluble in 1 per cent sodium hydroxide .
t
.