I. Determination of micro-carbon ferrochrome powder:
The national standard analysis has GB/T5687 1-1985 "micro carbon chromium iron powder chemical analysis" ammonium persulfate oxidation titration method chromium content practical methods are: titration method, the direct method of alkali fusion
: 1, titration method: acid or alkali dissolving sample (fuse) in - H2SO4 solution under the condition of the existence of AgNO3, using ammonium persulfate oxidation (as oxidant) trivalent chromium oxide into big chromium, bivalent manganese manganese oxide into 7 price, and then USES the Nacl will 7 valence of manganese reduction, bivalent chromium in ammonium ferrous sulfate titration, and according to the volume of the ammonium ferrous sulphate consumption to calculate percentage of chromium. Reagents: (1) H2SO41:4 (2) HNO3 concentration (d = 1.42), (3) (4) AgNO31.7 MnSO410% % 25% (0.5) (5) flow acid ammonium (now with current) 6. 5% Nacl solid 7 sulphur phosphorous acid mixture: 150, 150:700 (160:80-760) - H2SO4: H3PO4: H2O was a N phenyl anthranilic acid indicator: weigh and indicator 0.2 g dissolved in 100 ml of 0.2% of Na2CO3 solution pet-name ruby ammonium ferrous sulfate (100) standard solution: C [(NH4)2Fe(SO4)2] = 0.2mol /L(5+95=1000mL) In middle 3 analysis steps: Low carbon micro-carbon ferrochrome powder and medium-carbon micro-carbon ferrochrome powder: Said take 0.2000 g sample add 40 to 600 mL beaker ml1:4 - H2SO4 dissolve (low heat to dissolve the) add about 2 mL of HNO3 (1-2) boiling to remove nitrogen oxides, remove the add 100 mL hot water (more than 60 ℃) add 4 drops MmSO4 solution, add 15 m (10 mL) LAgNO3 solution (0.5%) and add 30 mL (20 mL) boiling flow acid ammonium solution, the solution changed from green to yellow to red, continue to boil for 2-3 (4-5) min large bubbles removed, Carefully add about 1.00g (10mL)NaCL (0.5% prepared) to the solid and boil for 100min to make the red color disappear. Before titration (add 200mL water drop and 30mL (60ml) thiophosphorous mixed acid), cool and add 5 (3) drops of N-phenyl o-aminobenzoic acid indicator. The solution is determined with ferrous ammonium sulfate standard solution, and the test solution color appears bright green as the end point. High carbon ferrochrome: Said take 0.2000 g sample of nickel in crucible, add 4 to 5 g sodium peroxide mix with a glass rod are within 700 ℃ Ma Fulu dissolved out 5-8 min and turn the crucible, wash all the outer wall of the crucible, put into 150 ml water, 600 ml beaker leaching in clinker and washed crucible in sulfuric acid solution, make the litmus paper presents acid reaction to heat and boil residue completely dissolved, add 4 drops of MnSO4 solution with 15 mlagno3 solution, (colour to yellow, purple, green) 30 ml ammonium persulfate solution boiling off, operation is the same as in the low carbon and carbon ferrochrome analysis operation.