Aluminum metaphosphate is a kind of raw material for optical glass, its purity directly affects the optical properties of optical glass. At present, there is no national standard test method for the purity detection of aluminum metaphosphate. The purity of aluminum metaphosphate in the industry is measured by testing the content of phosphorus pentoxide or alumina in aluminum metaphosphate, and then converted into the purity of aluminum metaphosphate by a certain coefficient.
At present, the determination of phosphorus pentoxide content in aluminum metaphosphate is adopted by quinoline phosphomolybdate gravimetric method, which has good precision and accuracy. The disadvantages are complicated analysis steps and long analysis period, and the preparation of precipitator uses two toxic organic compounds, acetone and quinoline, which bring great harm to the analysis and testing personnel, but also causes pollution to the environment. The test method of alumina content in aluminum salt provided by the fourth edition of the “Analyst Reader” (edited by Liu Zhen, Beijing University of Chemical Technology) is: add a certain amount and excessive standard m)TA solution in aluminum salt solution, heat and boil, after cooling with xylenol orange as an indicator, adjust the acidity of the solution to pH = 5-6, and use the standard solution of lead nitrate to drop back excessive EDTA. This method has high accuracy, but for testing the content of alumina in aluminum metaphosphorate, the analysis process is complicated, the analysis period is long, the sample needs mixed flux 900°C burning, the reagent type and dosage are relatively large, these factors will affect the accuracy of the test results.
The test method of alumina content in aluminum metaphosphorate is characterized in that it includes the following steps: 1) Weigh the dried sample 0.2g ~ 0.4g, add IOmL~20mL100g/L sodium hydroxide solution until the sample is completely dissolved, and add IOmL~20mL6mol/L hydrochloric acid until the solution becomes acidic; 2) Add 20mL~ 40mL0.05mol /L disodium ethylenediamine tetraacetic acid standard solution to shake the hook, add a few drops of phenolphthalein, neutralize with ammonia water until red, then adjust with hydrochloric acid until colorless and one drop too much; Add IOmL~20mL60% ammonium acetate, heat to boil, add 2 drops to 3 drops xylenol orange solution, titrate with zinc sulfate standard solution until red; 3) Add 30mL~40mL50g/L sodium fluoride solution, heat and boil, and then titrate with zinc sulfate standard solution until red is the remainder. C – The exact value of the concentration of zinc sulfate standard titration solution, expressed in moles per liter (mol/L); m – The value of the mass of the sample, expressed in grams (g); M one half the numerical value of the molar mass of aluminum oxide, expressed in grams per mole (g/mol). 2. The test method for alumina content in aluminum metaphosphate as described in Claim 1 is characterized by the 0? 2 ~ 0? 4g accurate to zero? OOOlg. 3. As for the test method of alumina content in aluminum metaphosphate mentioned in Claim 1, its feature is that the drying described in Step 1 is done by 105~IKTC. 4. The test method of alumina content in aluminum metaphosphate described in Claim 1 is characterized by the fact that the dried sample weighing 0. 2~0. 4g mentioned in step 1 shall be placed in a beaker. 5. As described in Claim 1, the test method of alumina content in aluminum metaphosphate is characterized by adding IOmL~20mL100g/L sodium hydroxide solution as described in Step 1, and then heating it on the electric furnace for several minutes. 6. The test method of alumina content in aluminum metaphosphate described in Claim 1 is characterized by the fact that the heating and boiling time described in step 2 and Step 3 is 3min~5min.
The invention provides a simple, rapid and accurate test method for alumina content in aluminum metaphosphates. Test method for alumina content in aluminum metaphosphate, which includes the following steps: 1) weigh the sample, add sodium hydroxide solution until the sample is completely dissolved, then add hydrochloric acid until the solution becomes acidic; 2) Add the standard disodium ethylenediamine tetraacetic acid solution to shake well, add a few drops of phenolphthalein, neutralize with ammonia water until red, then adjust with hydrochloric acid until colorless and one drop too much; Add ammonium acetate, heat to boil, add a few drops of xylenol orange solution, titrate with zinc sulfate standard solution until red; 3) Add sodium fluoride solution, heat and boil, and then titrate with zinc sulfate standard solution until red; 4) Result calculation. The invention adopts sodium hydroxide solution to quickly dissolve the sample, and has the advantages of easy operation, simple and rapid, and high accuracy.
