| 摘要 |
PROBLEM TO BE SOLVED: To provide a method in which the amount of impurities contained in a glass can be measured with satisfactory efficiency. SOLUTION: In the measuring method for the impurities in the glass by using ultrasonic waves, a glass plate in a prescribed thickness is made of a plurality of glasses whose impurity concentrations are different, the plate thickness of the glass plate is measured by the ultrasonic waves, a graph in which the measured value of the plate thickness is correlated with the concentration value of the impurities in the glasses is created in advance, a glass plate in the prescribed thickness is made of a glass whose impurity concentration is unknown in the same manner, the plate thickness of the glass plate is measured by the ultrasonic waves, and the concentration of the impurities is found on the basis of the plate thickness of the glass plate measured by using the correlation graph.
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