YS/T 1028.1-2015 English PDF (YST1028.1-2015)

This Part of YS/T 1028 specifies the method for the determination of total iron in lithium iron phosphate. This section applies to the determination of total iron in lithium iron phosphate. The measuring range is: 28% ~ 36%. 2 Summary of method After the sample is dissolved in hydrochloric acid, sodium tungstate is used as an indicator; a small amount of ferric iron is reduced to ferrous iron with titanium trichloride, to form and quot;tungsten blue and quot;; the excess trivalent titanium is naturally oxidized by the oxygen in the air. In the sulfuric acid-phosphoric acid medium, sodium diphenylamine sulfonate is used as an indicator, to titrate the divalent iron by the use of potassium dichromate standard solution. 3 Reagents and materials 3.1 Hydrochloric acid (1 + 1). 3.2 Sulfuric acid-phosphoric acid mixed solution: Slowly add 15 mL of sulfuric acid (¦Ñ¡Ö 1.84 g/mL) to 70 mL of water. After cooling, add 15 mL of phosphoric acid (¦Ñ¡Ö1.69 g/mL). Mix well. 3.3 Titanium trichloride solution (1 + 14): Take 2 mL of titanium trichloride solution (about 15% titanium trichloride solution). Use hydrochloric acid (1 + 5), to dilute it to 30 mL. 3.4 Potassium dichromate standard titration solution [c( ) = 0.0500 mol/L]: Weigh 2.4516 g of standard potassium dichromate (after predried at 140 ¡ãC ~ 150 ¡ãC for 2 h, place it in a desiccator and cool to room temperature). After dissolving in wat