1. Application

This applies to pH measurement method of green sand.

2. Definition

Green sand pH is hydrogen ion concentration.

3. Test apparatus and instrument

3.1 Measuring apparatus of pH using glass electrode (pH meter)

A meter of the precision higher than the type-II defined in JIS Z 8802 is used. Namely, reproducibility of pH measured on a standard solution must be within 0.05.
Method of adjustment and other basic matters are defined in JIS Z 8802. The glass electrode is as defined in JIS Z 8805.

3.2 Beaker

A clean polyethylene beaker of the capacity 1200ml is used.
Note: The reason for not using a glass beaker is that stirring of sand may cause increased alkali in the solution by beaker wall erosion, affecting the measurement result.

3.3 Stirrer

A magnetic stirrer for titration generally used in chemical analysis is used.
Note: Stirring must be done with a lid on the container, because stirring in open air tends to cause absorption of CO2, affecting the result.

3.4 Balance

A balance of the precision of 0.1g is used

4. Testing procedure

Sample of 20g is put in a cleaned beaker and 50ml of pure water is added. The sample is stirred for 30 minutes by a magnetic stirrer with a lid lightly put on the container. After waiting for settling, the clear upper part of the solution is checked for temperature and pH is measured by a pH meter. At the same time, pH of the original water is measured.

5. Record

The pH meter is read to the second decimal place and rounded off to the first decimal place for recording. Temperature at the measurement (normally 20 to 30 degree C) and pH of the pure water are also recorded.
Example: pH=8.2 (25 degree C, pure water pH=6.5)