Feb. a, 1924 
Digestibility of Tested Grain Hulls 
247 
cause it yields furfural on distillation with HC 1 , is presumed to be pen¬ 
tosan in nature. The latter two substances are so closely associated 
that they are grouped together under the term “lignin,” a complex con¬ 
taining a considerably higher percentage of carbon than does cellulose 
(about 60 per cent) and less resistant to the action of alkali. For this 
substance many formulae have been proposed. For a fairly complete list 
of these the reader is referred to a recent article by Beckmann, Liesche, 
and Lehmann (4). The most recent empirical formula possessed of any 
degree of definiteness is that of F. Lehmann ( 4 ), who suggests C 40 H 44016 . 
The work of Melander (32) is more recent, but his results are not con¬ 
clusive, several formulae being suggested. 
Klason’s conception that lignin is allied to coniferyl alcohol and de¬ 
rived from it by condensation and oxidation is worthy of consideration. 
The outstanding characteristic of lignin, and one on which almost all 
authorities agree, is the presence in the molecule of methoxy (CH s .O) 
and acetyl (CH 3 .CO) groups. These are readily split off by the action 
of heat and dilute alkali with the formation of acetic acid, the residue 
left behjnd being much more stable and insoluble than the original lignin. 
There are data to show that some of the methoxy groups are con¬ 
tained in the cellulose, but this is not definitely established, and the 
generally accepted idea is that the methoxy is characteristic of lignin. 
The subject is well summed up by Schorger (35) in a treatise on the 
chemistry of wood. 
THE ACTION OF SODIUM HYDROXID AND OTHER ALKALIES ON FIBER 
When such material as straw or wood is macerated with a solution of 
an alkali the solution becomes colored dark brown, and if the process is 
continued sufficiently the material is more or less completely disintegrated 
into a pulpy mass, which can be bleached by chlorin or any other suit¬ 
able bleaching agent to a white or nearly white substance. This residue 
is a crude form of cellulose, which, depending upon its subsequent use, 
may or may not be further purified. 
What are the changes involved in the destruction of the complex 
lignified tissue? What is it that the alkali removes? From this point 
on we shall consider only the action of dilute alkali on straw, as our 
problem is not the production of cellulose but simply the utilization of 
the principle in sufficient degree to render the fiber more digestible, at 
the same time holding at a minimum losses of valuable food substances. 
The most clear and concise explanation is that given by Magnus m 
his “ Theorie und Praxis der Strohaufschliessung” (30, p. 7 ~* 3 )- He 
considers that the reaction proceeds in a threefold manner: 
Separation and solution of the silicic acid, which constitutes f P or ^ipn of the in- 
crusting substance of the straw and is present in most straws to the extent of 1 to 2 
per cent, while some straws contain as much as 5 per cent. ,. - f 
^Splitting off of the methoxy and acetyl groups from the lignin, of which they form 
a characteristic part. This results in the production of acetic acid with consequent 
neutralization of more or less of the alkali employed m the process. The lignin 
itself is also profoundly changed and is rendered more insoluble and inactive. It 
should be borne in mind, however, that complete, or nearly complete, solution and 
removal of the lignin can be brought about when desired by repeated treatment witii 
alkali at higher temperatures than those successfully employed for straw hydrolysis. 
In paper manufacture this is what actually takes place. .. . 4 -™*+**** 
Forcing or springing of the bonds which link the lignin and cellulose together. 
The thewy of a linkage between these two substances in the fiber is advanced by 
Magnus, and he considers that the springing apart of these bonds is the most important 
74024 — 2 ' 
