PURPOSE: To achieve that the Hazen color number of a sample which is a solid at room temperature is measured accurately and visually by using a color-difference meter wherein a tube by a heating element surrounding a measuring cell is installed so as to prevent the sample from being solidified and a personal difference is not caused.
CONSTITUTION: A cell 1 in which no pasted part exists and which is composed of a test tube made of transparent quartz is surrounded by a cylindrical heating element 3 and a heat insulator 4, and a sample 2 which is a solid at room temperature is put into the cell 1 and heated. A beam of light from a light source 7 via a light passage installed in the heating element 3 and the heat insulator 4 its transmitted through the sample 2 which has been liquefied, and the Hazen color number is detected by a detector 8. When it is measured, a standard solution according to the Hazen color number stipulated by the JIS is first prepared, it is put into the cell 1, and a YI value is measured by a color-difference meter. Then, the YI value of distilled water is measured under the same condition, the difference ΔYI between the standard solution and the distilled water is found, the relationship between the ΔYI and the Hazen color number is changed into a graph and a calibration curve is formed. Then, the sample 2 is put into the cell 1, it is heated and liquefied, the ΔYI is measured, and the Hazen color number is measured by using the graph.
SAKURA KATSUHIKO
AKIMARU YUKIO
INOUE MASAFUMI
