ASTM D1832 Standard Test Method for Peroxide Number of Petroleum Wax
5. Apparatus
5.1 Iodine Flask, borosilicate glass, 250-mL capacity, glass-stoppered.
6. Reagents and Materials
6.1 Purity of Reagents - Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water - Unless otherwise indicated, references to water shall be understood to mean distilled water or water of equal purity.
6.3 Acetic Acid Solution - Mix 4 mL of concentrated hydrochloric acid (HCl, sp gr 1.19) with 996 mL of ACS special reagent grade glacial acetic acid (CH3CO2H). The acetic acid must pass the 1/2 h test for substances reducing K2Cr2O7.
6.4 Carbon Tetrachloride (CCl4).
6.5 Potassium Dichromate, Standard Solution (0.1 N) - Recrystallize potassium dichromate (K2Cr2O7) twice from an aqueous solution and dry at about 325°F (164°C) to constant weight. Dissolve 2.452 g of the purified K2Cr2O7 in water and dilute to 500 mL in a volumetric flask.
6.6 Potassium Dichromate, Standard Solution (0.01 N) - Dilute 100 mL of 0.1 N K2Cr2O7 solution with water to 1000 mL in a volumetric flask.
6.7 Potassium Iodide Solution - Dissolve 120 g of potassium iodide (KI) in 100 mL of water. Discharge any color from this solution as follows: put 1 mL of KI solution, 50 mL of water, and 5 mL of starch solution in a 300-mL flask and blanket with nitrogen or carbon dioxide. If a blue color develops, add 0.005 N Na2S 2O3 solution from a microburet until color just disappears. Calculate and add sufficient Na2S2O3 solution to the main KI solution to convert all free iodine to iodide. When starch solution is added to 1 mL of KI solution a blue color should not develop, but upon the addition of 1 drop of 0.01 N K 2Cr2O7 solution and 2 drops of concentrated hydrochloric acid (HCl, sp gr 1.19), a blue color should develop. Store this solution under chloroform by adding a few millilitres to the surface of the liquid.
6.8 Sodium Thiosulfate, Standard Solution (0.1 N) - Dissolve 12.5 g of sodium thiosulfate (Na2S2O3•5H2O) and 0.1 g of sodium carbonate (Na2CO3) in 500 mL of water. Let stand a week or more before using. Standardize against 0.1 N K2Cr2O7 solution. Restandardize at intervals frequent enough to detect changes of 0.0005 in normality.
6.9 Sodium Thiosulfate, Standard Solution (0.005 N) - Dilute 100 mL of 0.1 N Na2S2O3 solution with water to 2000 mL in a volumetric flask. Standardize against 0.01 N K2Cr2O7 solution.
6.10 Starch Solution - Dissolve 1 g of soluble starch plus a few milligrams of mercuric iodide (HgI2) in 100 mL of boiling water.
