Methods for chemical analysis of lithium carbonate,lithium hydroxide monohydrate and lithium chloride - Part 7: Determination of iron content-1,10-phenanthroline spectrophotometric method
1 Scope
This part of GB/T 11064 specifies the methods for determining the iron content in lithium carbonate, lithium hydroxide monohydrate and lithium chloride.
This part is applicable to the determination of iron content in lithium carbonate, lithium hydroxide monohydrate and lithium chloride, within the range of 0.00030%~0.030%.
2 Method summary
The test sample is decomposed with hydrochloric acid. Ferric iron is reduced to ferrous iron by ascorbic acid. In acetate buffer medium with pH3.5, ferrous iron and phenanthroline generate an orange-red complex. Measure the absorbance at the wavelength of 510 nm of spectrophotometer.
3 Reagents
Unless otherwise specified, analytically-pure reagents and secondary deionized water shall be used for purpose of this part.
3.1 Hydrochloric acid (1+1): guaranteed reagent.
3.2 Hydrochloric acid (1+7): guaranteed reagent.
3.3 Hydrochloric acid (2+1): guaranteed reagent.
3.4 Ammonium hydroxide (1+1): guaranteed reagent.
3.5 Ascorbic acid solution (25 g/L): prepared immediately before use.
3.6 Phenanthroline solution (2 g/L): weigh 0.2 g phenanthroline and dissolve it in 100 mL ethanol solution (1+1).
3.7 Acetic acid-sodium acetate buffer solution (pH3.5): weigh 16 g anhydrous sodium acetate, dissolve it in 500 mL beaker, add 170 mL glacial acetic acid, transfer it into a 1 000 mL volumetric flask, dilute it to the scale with water, and shake it well.
3.8 P-nitrophenol indicator solution (2 g/L): prepared with ethanol.
3.9 Iron standard storage solution: weigh 0.1430 g ferric oxide [w(Fe2O3)≥ 99.9%] which has been dried at 105°C ~ 110°C for 2 h and cooled to room temperature in advance, and put it in a 200 mL beaker. Add 20 mL hydrochloric acid (3.1), heat it at low temperature until it is completely dissolved, cool it, transfer it into a 1 000 mL volumetric flask, dilute it to scale with water, and shake it well. This solution contains 100 μg iron per 1 mL.
3.10 Iron standard solution: take 50.00 mL iron standard storage solution (3.9), put it in a 500 mL volumetric flask, dilute it to the scale with water, and shake it well. This solution contains 100 μg iron per 1 mL.
Foreword i
1 Scope
2 Method summary
3 Reagents
4 Apparatus
5 Test sample
6 Analysis procedures
7 Calculation of analysis result
8 Precision
9 Test report
