Why do conductivity measurements using glass instruments yield higher values?
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Does measuring conductivity in a glass container give a higher value? Why? I get lower readings when using plastic bottles compared to glass bottles, and the electrode placed at the bottom of the container gives higher readings than when it’s placed in the middle. Is there an explanation for this?
1. Glass containers and plastic bottles should have no impact on the sample in the short term. 2. Have the glass containers been cleaned thoroughly? III. What is the concentration of the standard solution? What is the approximate conductivity of the target substance to be measured?
It is pure water taken directly from the laboratory; the containers have been thoroughly washed with large amounts of water, and the measured value is below 5 μs/cm. The repeated comparison shows that glass bottles have a higher value than plastic bottles.
For the detection of very low conductivity, it is recommended to use plastic containers or containers made of quartz glass. In the production of ordinary glass, a certain proportion of soda ash is added to the raw materials. Ordinary glass is essentially a mixture that results from the melting and cooling of calcium silicate, silicon dioxide, and sodium silicate. Since sodium ions are soluble and will inevitably dissolve in water, this leads to an increase in the conductivity of high-purity water. Additionally, when measuring the conductivity of high-purity water, the static electricity generated by the container can also affect the stability of the measurement. It is recommended to use a container with a larger volume for these measurements, and to place the container on a grounded metal plate or to wrap it several times with thin copper wires before connecting it to the ground wire.