Feb. a, 1924 
Digestibility of Tested Gram Hulls 
255 
few minutes of the treatment there was always a noticeable formation 
of small bubbles, accompanied by a quite audible crackling sound sug¬ 
gestive of a mild effervescence. This phenomenon ceased to be per¬ 
ceptible after the first 15 or 20 minutes, which would seem to indicate 
a slowing up of the reaction and that the action of the alkali takes place 
largely in the first few minutes. These assumptions are borne out by 
the work of Magnus ( 30 , p. 12) and of Beckmann (3). 
The average amount of alkali consumed or neutralized in the process 
was 45 per cent of the total amount when the strength employed was 1 per 
cent; 46.66 per cent when the strength employed was 1.5 per cent; 24 per 
cent when the strength employed was 3 per cent. In other words, 
the percentage strength of the exhausted solutions averaged 0.45 per 
cent, 0.70 per cent, and 2.28 per cent, respectively, for the 1 per cent, 
1.5 per cent, and 3 per cent NaOH solutions. 12 
It will be noted that the percentage amount of NaOH consumed is 
about the same for the 1 per cent and 1.5 per cent—-around 45 per cent, 
or slightly less than half of the total amount employed—while the actual 
amount consumed is about the same for the 1.5 per cent and 3 per cent 
solutions, namely, about 0.7 per cent. 
Beckmann recommends the use of the exhausted alkali a second and 
even a third time, bringing it back to the desired strength by adding the 
required amount of fresh sodium hydroxid. In the practical operation of 
the process this procedure is in the interest of economy, but for our 
experimental work we considered it inadvisable, and accordingly a fresh 
solution was prepared for each lot of hulls. 
REACTION OP THE MATERIALS BEFORE AND AFTER TREATMENT 
In order to ascertain if there was any residual uncombined alkali in 
the treated materials, the water-soluble acidity or alkalinity of all the 
treated and untreated samples was determined according to the method 
given in the manual of the Association of Official Agricultural Chemists. 13 
Table II sets forth the results. 
Table II.— Water-soluable acidity or alkalinity of untreated and treated hulls 
Labor¬ 
atory 
No. 
248 
503 
293 
453 
49 1 
482 
337 
321 
512 
449 
460 
485 
494 
Material. 
N/10 NaOH 
required 
per gram of 
substance. 
Oat hulls, untreated. 
Cc. 
0. 23 
. 10 
Oat hulls, treated 1 per cent NaOH. 
Oat hulls, treated 1.5 per cent NaOH. 
Barley hulls, untreated. 
1.14 
• 23 
.42 
. 22 
Barley hulls, treated 1 per cent NaOH. 
Barley hulls, treated 1.5 per cent NaOH. 
Rice hulls, untreated. 
Rice hulls, treated 1.5 per cent NaOH. 
Rice hulls, treated 3 per cent NaOH. 
Cottonseed hulls, untreated. 
•23 
.08 
•47 
.08 
Cottonseed hulls, treated 1.5 per cent NaOH. 
Flax shives, untreated. 
Flax shives, treated 1.5 per cent NaOH. 
N/10 H2SO4 
required 
per gram of 
substance. 
Cc. 
O. 16 
.07 
. 08 
w The 3 per cent NaOH solution was used in only one instance, hence the corresponding value does not 
represent an average. 
18 Association of Official Agricultural Chemists, op. ciT., p. q8 . 
