HI70300S is a storage solution prepared with reagent grade chemicals that can be used to ensure optimum performance of your pH and ORP electrodes. It is necessary to store a pH electrode in a solution in order to keep the glass membrane of the pH electrode hydrated. Ideally a storage solution should be used; never store an electrode in distilled or deionized water. The Hanna Instruments storage solution is specifically formulated to minimize microbial growth and to prevent any effects of diffusion/osmotic from storing a probe in a solution with the highly concentrated inner reference electrolyte. Storing your pH and/or ORP electrodes in a storage solution will also keep the junction clear. Maintaining the hydrated layer and clear junction will help to ensure a fast and reliable measurement. In the case of cleaning your pH electrode in one of our cleaning solutions, we recommend soaking the electrode in the HI70300S storage solution for at least one hour before taking measurements. Special formulation to minimize microbial growth and osmotic/diffusion effects between the solution and inner reference electrolyte Manufactured specifically for pH and ORP electrodes Clearly marked expiration date and lot number