HI70300-012 is a GroLine 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 diffusion/osmotic effects 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 HI70300-012 GroLine storage solution for at least one hour before taking measurements.