The iodine solution Colorimeter is composed of a series of solutions containing different amounts of iodine in 0.5N potassium iodide aqueous solution. Because the iodine content is different, the solutions are also dyed in different shades of colors. Its basic solution is a solution containing 4000 mg of iodine in 100 ml of 05N potassium iodide solution. Each level of solution in the Colorimeter is prepared by diluting the previous level of solution 1, 3 times. (Related instrument: Colorimeter)
In order to more accurately identify the iodine content of the solutions at all levels, the iodine content of all solutions must be checked by thiosulfate titration.
After dilution of the basic solution, the following color grades are obtained, and the numbers indicate the milligrams of iodine in 100 ml of the solution:
In order to make the solutions at all levels not easy to fade, a few drops of concentrated sulfuric acid were added to the basic solution during preparation. The effective use period of iodine solution has a certain period of time. Generally, the iodine solution must be checked according to the standard every 6 months.
Pour the solution prepared in this way into a closed test tube (80 mm long, 9-5 mm outer diameter, 7.5 mm inner diameter.). Store the tubes on the tube racks inside the box (Figure 55). Push the tube rack into the box, so that the test tubes can be stored in the dark forever. On the tube rack, a ground glass is installed behind the test tube.
The iodine Colorimeter can be placed in an open box. The box contains a removable tube rack covered with dark swanner (Fig. 56). There are jacks for containing iodine solution test tubes up and down the tube rack. There are two jacks for holding empty test tubes for the test material. The bottom of the box is also the background of the color comparison place, which is covered with white powder paper.
The sample is poured into a test tube of the same size and made of the same glass as the closed standard test tube. Then compare the color of the sample with the colors of the standard test solutions at all levels. For example, if the color of the lacquer is darker than a solution containing 376 mg of iodine and lighter than a solution containing 489 mg of iodine, the color of the lacquer can be represented by two numbers "376-489". Table 20 lists the colors of various varnishes as measured by the iodine solution Colorimeter specified in Standard 93.
