Cellulose microcrystal suspensions were prepared
by treating bleached softwood kraft pulp
with 65% (w/w) sulfuric acid or 4 N hydrochloric
acid. To obtain a good dispersion of HCl-treated
microcrystals, a more thorough removal of acid
from the hydrolysate was necessary than in the
case of H2SO4. Conductometric titration showed
that the H2SO4-treated sample had a surface
charge of 84 mmol kg−1 of strong acid and
26 mmol kg−1 of weak acid, ascribed to sulfate
ester and carboxyl groups, respectively. No strong
acid groups and a small amount of weak acid
groups (0.5% (w/v) and rheopectic