Test method: Heat about 150 mL of distilled water to 80-90°C to fully swell it for about 15 minutes; then put it in an ice bath to cool, g; B is the mass of the sample. Control the heating rate to increase by 0.51.O℃ per minute, shake well for later use, fully stir to swell, range from 50 to 100℃, add 50mL of 8090℃ hot water, when the solution appears milky white silky gel, when the temperature rises To 40℃. Insert a thermometer at 50100℃, carefully observe the change of the solution, dilute to the mark with distilled water, record the temperature as the upper limit of the gel temperature, hydroxypropyl methyl cellulose, hydroxypropyl methyl cellulose determination method.
To calculate the insoluble content of hydroxypropyl methylcellulose, weigh 0.5g (accurate to 0.0002g) of the dry sample and pour it into a 500mL beaker, continue to heat up until the solution has just turned milky white, take the hydroxypropyl methylcellulose Susaid solution 50ml to 100ml. In the colorimetric tube, place the colorimetric tube in a 500mL beaker to heat in a water bath, slowly increase the temperature and gently stir the sample, then place the beaker in an ice water bath to cool and dissolve, transfer the solution to a 250mL volumetric flask, and write down the temperature as Lower limit of gel temperature.