The pH value of HPMC (hydroxypropyl methylcellulose) depends on its concentration in the solution, temperature, and the quality and purity of the water used. Typically, the pH value of HPMC in aqueous solution is between 5.0 and 8.0, depending on the dissolution conditions and the specifications given by the manufacturer.

1. Basic properties of HPMC
HPMC is a non-ionic cellulose derivative commonly used in the pharmaceutical, food and cosmetic industries, with good film-forming, thickening and stability. It is non-ionic, soluble in cold water but not in hot water, and the solution is generally neutral or slightly acidic. In industrial applications, HPMC is widely welcomed for its safety and relatively stable properties.

2. pH range of HPMC aqueous solution
According to laboratory data and literature research, the pH value of HPMC in low-concentration aqueous solutions (such as 1-2%) is generally between 5.0 and 8.0. The product instructions provided by the manufacturer usually give a similar pH range for users to refer to during the configuration process. For example, the pH value of some HPMC products in a 0.1% aqueous solution is about 5.5 to 7.5, which is relatively close to neutral.

Low concentration solution: At low concentration (<2%), the pH value of HPMC after dissolving in water is generally close to neutral.

High concentration solution: At higher concentrations, the solution viscosity increases, but the pH value still fluctuates in a range close to neutral.

Effect of temperature: The solubility of HPMC is greatly affected by temperature. It is easily soluble in cold water and easily precipitated in high temperature water. When preparing HPMC solution, it is usually recommended to use cold water to avoid solubility changes caused by excessively high temperature.

3. pH value detection and influencing factors
Usually, during production and use, when detecting the pH value of HPMC aqueous solution, a calibrated pH meter is used for direct measurement. However, the following factors may affect the measurement results:

Water purity: Water from different sources may contain dissolved salts, minerals, etc., which affect the pH measurement results. It is generally recommended to use deionized water or distilled water to prepare HPMC solution to ensure the accuracy of the results.
Solution concentration: The higher the HPMC concentration, the greater the viscosity of the solution, which brings certain difficulties to pH measurement, so low concentration (<2%) solutions are generally used.
External environment: Temperature, calibration of measuring instruments, etc. may cause slight pH deviations.

4. pH requirements in HPMC application scenarios
When HPMC is used in food and medicine, its stability and pH adaptability need to be considered. For example, in pharmaceutical tablets and capsule preparations, HPMC is used as a thickener, sustained-release agent and coating material, and pH stability is an important consideration. Most drugs need to be released in a near-neutral or slightly acidic environment, so the pH characteristics of HPMC are very suitable for this purpose.

Food industry: When HPMC is used as a thickener and stabilizer, it is usually hoped that its pH value is close to neutral so as not to affect the taste and stability of the product.
Pharmaceutical industry: In tablets and capsules, HPMC is used to control drug release, and a stable pH close to neutral helps maintain the activity of the drug.

5. Adjustment method of pH of HPMC aqueous solution
If the pH value of HPMC solution needs to be changed in a specific application, it can be fine-tuned by adding acid or alkali. For example, a small amount of dilute hydrochloric acid or sodium hydroxide solution can be used, but it must be carefully controlled to avoid exceeding the safety range or affecting the stability of HPMC.

The pH value of HPMC in aqueous solution is generally between 5.0 and 8.0, which is close to neutral. The pH requirements for different application scenarios may be slightly different, but usually no special adjustment is required.