The relation between the value of Q/Q1 and the carbonization temperature of coal has been studied for various coals. The shape of the curve depends on the grade of coal. It is significant that the Q/Q1 of both the full-line and the dotted line in strongly caking coal suddenly decreases at higher temperatures. Most of the curves have a second minimum value which is smaller than that of the curve for the aqueous solution. This can be understood by taking account of the difference in dielectric constant between the coal and the aqueous solution. This result seems to support the existence of the dotted line in Fig. 2, as well as the opinion in Ref. 14 that the factor, p, would be very important.