Type 72 spectrophotometer is used for the research on the concentration range of methy-lene blue solution which coin cides with the law of light absorption and the selection of the wavelength.

The effects of electrolyte (different types and different ion strength) on critical concentration (C *) of the chitosan and N alkyl chitosan liquid crystalline in formic acid solutions were studied.

Critical concentration(c  )of the samples were measured by polar optical microscopy(POM).

It was showed that,when the concentration of dosed NaCl solution reached the critical salt concentration,there would generate the phenomenon of particles releasing in sand column;in mixed salt solution,the existence of molar percent of Ca2+ would inhibit the .

The results indicate that critical salt concentration and critical flow rate exit on the saltwater-freshwater interface.

With horizontal seepage experiments,this paper analyzes the critical salt concentrations(CSC)of the different cations,by examining such solutions as NaCl,KCl,LiCl,NH_4Cl,CaCl_2 and MgCl_2,which can cause the particle release of water sensitivity of porous media.