The pyrolysis of silica gels surface-treated with (A) methanol, (B) ethanol, (C) n-propanol and (D) isopropanol has been investigated by means of QPMS or GC-QPMS. The thermal decomposition takes place on the following three ranges, i. e., (i) in the vicinity of ca. 150°C, (ii) in the range of 200-300°C and (iii) 300-500°C. The amount of gas evolved showed the most appreciable rate in the range of (iii) and had the maximum in the vicinity of 400-450°C. In the case of silica gels surface-treated with (A) methanol, the range of (iii) was extended over 300-800°C and the amount of gas evolved had the maximum rate in the vicinity of 550-600°C which was higher than the ones of silica gels surface-treated with other alcohols. The mass spectra of vapors evolved in the respective temperature range were observed and their constituents were analysed. The followings were found from them that (1) the physisorbed water and unreacted alcohol were released in the range of (i); (2) the released water in the ranges of (ii) and (iii) was regarded as the water due to condensation of unreacted surface silanols ; (3) vapors evolved in the range of (ii) was mainly alcohol due to hydrolysis of surface groups with the water arised from the condensation of unreacted surface silanols ; (4) vapors evolved in the range of (iii) included the alcohol, but principal constituents were confirmed to be CO with minute amount of CH4 and H2 in the case of (A), CH2=CH2 with a small amount of CH3CHO in the case of (B), CH3CH=CH2 with small amount of CH2=CH2 and CH4 in the case of (C) and only CH3CH=CH2 in the case of (D), respectively ; (5) these constituents were also confirmed by using GC-QPMS ; (6) the mechanisms were suggested to account for thermal decomposition of the surface groups ; (7) from these results, the surface groups thus formed were confirmed not to be the alcohol chemisorbed on the silica gel, but to the alkoxy groups formed by the condensation of the surface silanol with alcohols.
After a short discussion on the method of the dispersion curve fot the evaluation of the dispersibility of pigments, an attempt is made to establish the dispersibility by means of a new criterion, the''effectiveness', which takes into consideration not only the energy expenditure, but also the amount of dispersed pigment. By means of grinding tests it is shown that for every pigment/vehicle systcm there is an optimum proportion for the economy of the milling pi ocess or, in other words, an 'optimal effectiveness'. The physical factors determining the shape of the 'effect : veness' curve are briefly discussed and a method is suggested to obtain the optimal effectiveness with a lesser effort. If the volume ratios, instead of the weight ratios, are considered for the calculation of the effectiveness it can be shown that the effectiveness optimum in a given vehicle solution is variable within a narrow range for most pigments. Further research has shown that the effectivness curve can also be obtained by using the development of tinting strength instead of the fineness of grind as criterion for the dispersibility.