The stability of nitric acid oxidized carbon nanotubes (CNTs) and the precipitation of oxidized CNTs in water by salts were investigated. Stability investigation shows that during an aging time of 30 days, oxidized CNTs dispersion shows characteristic UV-vis absorbance peak of individual CNTs at 252 nm and CNTs concentration in the dispersion after 30 d aging is 85% of the initial concentration. The precipitation value of salts were measured and the precipitation value follows the order of NaCI > KCI > 1/2(MgCl2) > 1/2(CaCl2) > 1/3(FeCl3) > 1/3(AlCl3). The nature of anions investigated has little effect on precipitation values of salts. (c) 2008 Elsevier B.V. All rights reserved.