The HI7072 1M KNO3 (potassium nitrate) electrode fill solution is chloride free. It is mainly used as a reference fill solution for Bromide, Cadmium, Chloride, Cupric, Cyanide, Iodide, Lead/Sulfate, and Silver/Sulfide electrodes. It can also be used as an alternative to 3.5 M KCl (potassium chloride) fill solution used in double junction refillable electrodes when taking pH measurement of samples that have heavy metals such as silver, lead, and mercury. These heavy metals can react with the 3.5M KCl solution to form insoluble chloride salts. Any precipitation in the liquid junction will interfere with the reference potential resulting in erratic readings.
Hanna’s double junction system has two junctions, only one of which is in contact with the sample as shown in the figure below. The likelihood of clogging the outer junction is ordinarily reduced with a double junction electrode since the outer reference cell uses a fill solution that is “silver-free” to prevent precipitate from forming that will clog the junction. The HI7072 electrolyte solution is also “chloride-free” which minimizes precipitation from solutions containing heavy metals. The HI7072 ensures optimum measurement performance from your pH electrode.