（1） Determination of silicon (ferrous reduction of silicon molybdenum blue photometric method)
1. Method summary
The sample is dissolved in dilute sulfuric acid and oxidized by potassium permanganate. All silicic acid ions are converted into orthosilicic acid and react with ammonium molybdate to form aluminosilicate heteropoly acid. Then, in the presence of oxalic acid, it is reduced to silicomolybdate blue by ferrous iron, and then the photometric determination of silicon is carried out.
2. Reagents
(1) Dilute nitric acid (1 + 5)
(2) Potassium permanganate solution (2%)
(3) Basic ammonium molybdate solution:
A. Ammonium molybdate solution (9%)
B. Ammonium carbonate solution (18%)
A. B two solutions are combined in equal volume and stored in plastic bottle for standby.
(4) Oxalic acid solution (2.5%)
(5) Ammonium ferrous sulfate solution (1.5%)
Weigh 15g ammonium ferrous sulfate, first wet 1ml dilute sulfuric acid (1 + 1) ferrous salt, then dilute to 1L with water, dissolve and shake well for standby.
3. Analysis steps
Weigh 30mg of sample and add it into a high type beaker (250ml). Add 10ml of preheated dilute nitric acid (1 + 5) into the cup, dissolve the product, remove the yellow gas, add 2-3 drops of potassium permanganate (2%), continue to heat until boiling, add 10ml of basic ammonium molybdate solution, shake for 10 seconds, then add 40ml oxalic acid (2.5%) and 40ml ammonium ferrous sulfate (1.5%) and shake well. Take water as reference, deduct blank, 1cm Special colorimetric dish, direct reading content.
4. Precautions
(1) The sample should be dissolved at low temperature.
（2） Determination of manganese (ammonium persulfate Silver Salt Spectrophotometry)
1. Method summary
In the medium of nitric acid and phosphoric acid, silver ion is used as catalyst to oxidize low valence manganese to permanganate in nitric acid and phosphoric acid medium, and manganese is determined by spectrophotometry.
2. Reagents
(1) Mixed solution of manganese
Methods: 450 ml nitric acid, 72 ml phosphoric acid and 7.2 g silver nitrate were diluted to 2 l with water, shaken up, and stored in a brown bottle for standby.
(2) Ammonium persulfate solution (15%) or solid.
3. Analysis steps
Weigh 50mg of sample, put it into a high type beaker (250ml), dissolve it in 15ml of preheated manganese fixing solution, add 10ml of ammonium persulfate solution (15%) when the sample is dissolved (1g of solid ammonium persulfate is added in the joint test) and continue to heat until it boils and large bubbles appear. After about 10 seconds, add 40ml of water and pour it into the cuvette to read the content directly.
4. Precautions
(1) After adding ammonium persulfate, the boiling time should be controlled for 10 seconds.
(2) When recording the content, read it after a small amount of small bubbles escape.
（3） Determination of phosphorus (sodium fluoride stannous chloride phosphomolybdate blue photometric method)
1. In nitric acid medium, the sample is oxidized with potassium permanganate to oxidize metaphosphoric acid to orthophosphoric acid, and form phosphomolybdic acid with ammonium molybdate, and then reduced to phosphomolybdate blue with stannous chloride for photometric determination. Tartaric acid ions eliminate the interference of silicon. Sodium chloride complexed iron ion to form colorless complex and inhibit the ionization of nitric acid.
2. Reagents
(1) Oleic acid (1 + 2.5)
(2) Potassium permanganate solution (2%)
(3) Ammonium molybdate potassium tartrate solution
Take the same volume of ammonium molybdate solution (10%) and potassium sodium tartrate (10%) and mix them for standby.
(4) Sodium fluoride (2.4%) - stannous chloride (0.2%) solution;
24g sodium fluoride is dissolved in 800ml water, which can be slightly heated to aid dissolution, 2G stannous chloride, 5ml diluted hydrochloric acid (1 + 1), heated until completely dissolved; add the above solution, dilute with water to 1L, and filter if necessary. When used on the same day, a large amount of sodium fluoride solution can be prepared. When using, take out part of the solution and add the specified amount of stannous chloride.
3. Analysis steps
Weigh 50mg of sample, put it into a high type beaker (250ml), add 10ml of preheated dilute nitric acid (1 + 2.5), heat until the sample dissolves, escape the yellow gas, and drop 2-3 drops of potassium permanganate solution (2%). Continue to heat and boil for 10 seconds. Add 10 ml ammonium molybdate potassium sodium tartrate solution and shake well. Then add 40 ml sodium fluoride stannous chloride solution. Water as a reference, pour into the cuvette, read the content.
4. Precautions
(1) During oxidation, the solution should be boiled and kept for 5-10 seconds.
(2) The operation procedures of the analysis are relatively consistent to ensure the repeatability and accuracy of the analysis results.
(3) When the content of 40 is higher than 0.050%, the time of color stability is short, and the reading should not be delayed, even shorter when the content is 0.080%.
Operation method of NJS microcomputer high speed analyzer
1. Zero adjustment of the instrument (Note: distilled water is required in three cups)
(1) According to channel 1, (2, 3);
(2) Adjust the corresponding full rotation group to make the corresponding data about 95;
(3) Press exit instrument to reset to zero automatically.
2. Enter the content value of the standard sample
(1) According to channel 1, (2, 3);
(2) Adjust the corresponding full scale knob to make the corresponding data about 95;
(3) Press the drain button to drain the distilled water from the cup;
(4) Pour the colored standard sample solution into the corresponding colorimetric cup;
(5) According to the function;
(6) According to the numerical value (Note: the value refers to the content value of the standard sample);
(7) According to function 9 and 1;
(8) Press exit to complete the input.
3. Test sample
(1) According to channel 1, (2, 3);
(2) Adjust the corresponding full scale knob to make the corresponding data about 95, and then press exit;
(3) Drain the distilled water from the cup;
(4) Pour the colored sample solution into the corresponding cuvette;
(5) The displayed data is the percentage value of the sample, (Note: I is the determination of manganese, II is the determination of silicon, and III is the determination of phosphorus);
(6) After measuring, drain the solution in the cup and pour it into distilled water.