THE UTILIZATION OF CERTAIN PENTOSES 
381 
According to this method the ground straw was boiled in 5 percent 
KOH for I hour, the extract pressed out with a fruit press and filtered 
through cloth. Fehling's solution was added in the proportion of 
one half liter to every 300 g. of straw used. The precipitate was 
separated by filtration, washed and treated with an alcoholic solution 
of hydrochloric acid. It was washed several times with 60 percent 
alcohol, dried and dissolved in dilute KOH and again precipitated 
with Fehling's solution. It was then washed and acidified as before 
and finally freed from chloride and dried. 
Salkowski considered that xylan prepared according to this method 
was practically free from araban and other hemicelluloses, cellulose 
and starch, and that it was nearly pure. 
This preparation yielded 74.0 percent xylan, according to Krober's 
tables,^^ when analyzed according to Tollens' phloroglucid method 
for the determination of pentosans, which is one percent more than 
was found in the xylan prepared according to Schone and Tollens' 
method and analyzed in the same way. The commercial preparation 
of xylan used in these experiments gave 86.1 percent of the the- 
oretical amount. The xylan prepared according to Salkowski's 
method dissolved in i percent KOH had a specific rotation, [a]D, 
of — 83°. It contained 0.5 percent ash. Swartz^^ mentions some 
which she prepared which yielded 72.0 percent of the theoretical amount 
according to Krober's tables. She found the specific rotation of one 
sample to be — 83°. Tollens gives the specific rotation of xylan from 
wheat straw as — 84.1°. Swartz's determinations of ash in the 
xylan were somewhat higher than those obtained in the present 
study while Salkowski reports that some of his preparations contained 
as low as 0.7 percent ash. 
The xylans prepared by both ToUens's and Salkowski's methods 
were tested for galactan and methyl pentosans with negative results. 
No starch was present. It is apparent from the above described 
experiments that the compounds prepared were composed largely of 
xylose. 
The first series of experiments was made with the two pentose 
sugars as compared with glucose as a source of carbon. The sugars 
were added to the solutions of nutrient salts in quantity to make 
28 Wiley, H. W., et al. Official and Provisional Methods of Analysis. Asso- 
ciation of Official Agricultural Chemists. U. S. Dept. Agr., Bur. Chem. Bull. 107. 
1907. 
2^ Swartz, Mary Davies. Loc. cit. 
