56 BULLETIN 80, U. S. DEPARTMENT OF AGRICULTURE. 
color in the samples tested for the determination of the amount of bleach required. 
The bleached sample was thoroughly washed, first with hot distilled water and after- 
wards with ethyl alcohol. Its bone-dry weight was then determined. The per- 
centage loss on bleaching is based on the bone-dry weight of the unbleached pulp, 
which had been calculated from its bone-dry factor. 
Microscopic examinations. — Representative portions from the pulp sheets were 
soaked in water, teased apart with a needle, stained with Bismarck brown, dehydrated 
with absolute ethyl alcohol, cleared in xylol, and made into permanent mounts with 
Canada balsam. Photomicrographs of these mounts magnified 65 diameters were used 
in studying the individual fiber characteristics. Further microscopic study of each 
of the individual mounts was also made, using different magnifications, and such 
features were observed as the apparent strength of cell walls, the prominence of cell 
markings and the presence of vessels, fiber bundles (shives), and ray cells. The 
general shape and condition of the fibers and the distinguishing characteristics for 
the species were noted. By means of a micrometer eyepiece about 50 unbroken 
fibers from the various mounts were measured for length and breadth at the middle 
of the fibers, and the average thickness of the cell walls was roughly estimated. The 
fibers were selected at random, no effort being made to select extremely long or short 
ones. 
ANALYSES OF SODA LIQUORS. 
The caustic-soda solutions charged and the black liquors from the leached pulps 
were examined for their contents of cooking chemicals, in the first case to calculate 
sizes of charges, and in the second to determine the consumption of caustic soda during 
cooking. 
Caustic soda liquor. — The examination of the caustic soda liquor was conducted as 
follows: A 10 cc. portion was titrated against normal sulphuric acid, using phe- 
nolphthalein as first indicator and methyl orange indicator to finish the titration. 
Letting Y=the number of cubic centimeters of normal acid solution required for 
the first end point and X=the number of cubic centimeters required for the final 
end point, the following equations were used for calculating the concentration of 
caustic soda (NaOH) and the causticity: 
4 (Y-(X-Y))=grams per liter of NaOH. 
IQO(Y-fX-Y)) 
— — y -=per cent causticity. 
Black liquor. — The examination of black liquor was conducted as follows: 
(1) A 50 cc. portion of black liquor was evaporated to dryness in a platinum dish. 
The residue was ashed over a Bunsen burner and the soluble salts were leached out 
with hot distilled water. The entire solution obtained was titrated with normal sul- 
phuric acid, using methyl orange as indicator. The number of cubic centimeters of 
acid required to produce the end point multiplied by 0.62 gives the grams per liter 
of total sodium oxide (Na 2 0) in the black liquor. 
(2) A 100 cc. portion of the same black liquor was mixed with 50 cc. of 10 per cent 
barium chloride solution in a 500 cc. calibrated flask. The mixture was then diluted 
to 500 cc. with neutralized or freshly distilled water free from carbon dioxide and 
thoroughly agitated . After settling, 50 cc . of the clear supernatant liquor were titrated 
with tenth normal hydrochloric acid, using phenolphthalein as indicator. The num- 
ber of cubic centimeters of acid required for the end point multiplied by 0.401 gives 
the number of grams per liter of free caustic soda (NaOH) in the black liquor. 
(3) The causticity of the black liquor was calculated from the following equation: 
A (0.775) 100 
— - — —■ =per cent causticity. 
In which: 
A=the number of grams per liter concentration of caustic soda (NaOH). 
B=the number of grams per liter concentration of total sodium oxide (Na^O). 
