The properties of cellulose microcrystals and their colloidal suspensions obtained by acid treatments of native
cellulose have been investigated. Bleached softwood kraft pulp was treated with 65% (w/w) sulfuric acid or 4 N
hydrochloric acid and the resulting particle morphology and flow properties of the aqueous suspensions were studied.
Colloidal dispersion of the HCl-treated sample was obtained by more thorough removal of acid from the hydrolysate
than in the case of H2SO4 treatment. The H2SO4-treated and HCl-treated samples had similar particle sizes and
shapes when observed by electron microscopy. Conductometric titration of suspensions revealed that the
H2SO4-treated sample had a surface charge of 84 m-equiv kg−1 dry material due to the introduction of sulfate groups,
while that of the HCl-treated sample was undetectable. The H2SO4-treated suspension showed no time dependence in
viscosity, while the HCl-treated suspension was thixotropic at concentrations >0.5% (w/v) and anti-thixotropic