Abstract: The dependence of the intrinsic viscosities of polyacrylamide(PAM)and hydrolyzed polyacrylamide(HPAM) in water on the concentration of added salt (sodium nitrate) and time was studied.The intrinsic viscosities of HPAM decrease with the increase of the concentration of added salt.When the salt concentration is high,the ratio[η)/M is inversely proportional to the concentration of salt added to the polyelectrolytes. The Solution instability of PAM and HPAM was examined in 1M NaNO₃ aqueous solution for samples with different molecular weight and hydrolyzed degree. The solution viscosities decrease with time. After a certain period of storage the ratio ((ηsp/C)t₀-(ηsp/C)ti)/(ηsp/C)t₀ is found to be proportional to the logarithm of M_w. M_w stands for the apprent molecular weight of HPAM