【Daily Question】Chemical Analysis Version, 2021.12.4
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The reference substance for calibrating the I2 standard solution is: A、As2O3 B、K2Cr2O7 C、Na2CO3 D、H2C2O4 A
For safety reasons, potassium dichromate is generally used to standardize sodium thiosulfate, which is then used to standardize iodine. Therefore, the reference substance for standardizing iodine is potassium dichromate.
From the perspective of answering the question, A should be chosen: it is Method 1 specified in GB 601, and there is no option for sodium thiosulfate in the question. The actual operations are mostly as described by Haiyou on the 6th floor.