In this paper, the conductivities of double-distilled water and aqueous solution of NaCl, HOAc, C_5H_5N, etc. were determined in an elongated time period. It is found that the conductivity values of the solutions at certain temperature are not constant and change over time. On a large time scale, the variation trajectories can be divided into two groups. The one is that the conductivities increase with time increase, known as "water type trajectory"; and in the other the conductivities decrease with time increase, known as "pyridine type trajectory". Contrast experiments showed that the "water type trajectory" would be obtained with the promoter of water structure, and "pyridine type trajectory" would be obtained with damager of water structure. They would be related to the strength of electromagnetic field radiation in natural surroundings.

Key words: ELECTRICAL CONDUCTIVITY, AQUEOUS SOLUTION, TIME, CHANGE, ELECTROMAGNETIC FIELDS