The pH of Sodium Iodide in Water

The pH of a sodium iodide (NaI) solution is greater than 7, indicating that it is basic. This is because NaI is a salt of a strong base (NaOH) and a weak acid (HI), leading to the formation of a basic solution when dissolved in water. The pH range of an NaI solution is 8-9.5, as stated in ChemicalBook.

Solubility and Stability of Sodium Iodide

Sodium iodide is highly soluble in water, with a solubility of 1842 g/kg at 25°C, as shown in the solubility data provided by Wikipedia. It is also soluble in various organic solvents, including liquid ammonia, liquid sulfur dioxide, methanol, formic acid, acetonitrile, acetone, formamide, and acetamide, as detailed in the solubility table from Wikipedia.

The stability of sodium iodide is affected by atmospheric oxygen, which can oxidize iodides to molecular iodine (I2), leading to a yellow coloration. To maintain the stability of NaI, it should be stored under dark, low-temperature, and low-humidity conditions.

Impurities and Contaminants

PH of sodium iodide in waterImage source: picryl

When it comes to contaminants, the presence of impurities in sodium iodide can affect its properties and applications. For instance, the presence of hydrazine in NaI solutions should be kept below 5 ppm to ensure product quality, as mentioned in the product specifications from Deep Water Chemicals.

Balancing the pH of Sodium Iodide Solutions

To balance the pH of an NaI solution, one can add a strong acid or a weak acid to neutralize the basic properties of the solution. For example, adding hydrochloric acid (HCl) or acetic acid (CH3COOH) to an NaI solution can help bring down the pH to the desired level. However, it is essential to carefully control the amount of acid added to avoid overshooting the target pH.

See also  The pH of Potassium Iodide in Water

Alternatives to Sodium Iodide

As an alternative to using NaI, one can consider using potassium iodide (KI) as a source of iodide ions. KI has similar properties to NaI but is less hygroscopic, making it more suitable for certain applications. Additionally, KI is also used in organic synthesis and as a nutritional supplement, similar to NaI.


In summary, the pH of a sodium iodide solution is greater than 7, and it is affected by the presence of impurities and storage conditions. To balance the pH, one can add a strong or weak acid, while considering alternatives like potassium iodide for specific applications.

– Sodium iodide | 7681-82-5 – ChemicalBook (
– Sodium Iodide | NaI | CID 5238 – PubChem (
– Sodium iodide – Wikipedia (
– A water solution of NaI will exhibit a pH value of: a. greater than 7. b … (
– Sodium Iodide – Deep Water Chemicals (