In the determination of zinc in manganese brass, for less manganese, can be in the ammonia medium. Manganese (L) was oxidized to insoluble manganese dioxide by using qian-chuan-su as oxidant, and zinc was determined. When the content of manganese is above 2% , as zhmn 57-3-l. Potassium chlorate or persulfate should be used as oxidant in nitric acid medium. In this way, hydrated manganese dioxide can be obtained and manganese can be separated, but the separation of manganese is incomplete. This article is based on this. The shielding tests of nitric acid medium, potassium chlorate dosage, heating time and interference ions after separation were carried out. To ensure complete manganese dioxide of hydration. Need to use concentrated nitric acid, not dilute nitric acid, potassium chlorate after separation of the filtrate. According to the test of persulfuric acid, the content of manganese is very small, and the filtrate is screened by potassium fluoride, sulfur vein, barium chloride, etc. . Complexometric titration with Edta is a simple method. The accuracy of the analytical results is in line with the experimental requirements and can be used for the determination of zinc in nickel-free manganese brass.

1. Reagent and instrument Barium chloride solution: 109 l-1'sodium sulfate, sulfur suit Banyan Solution: 1. Bao L-'-hexamethylenetetramine: 3009 IJ-'-Methyl orange, xylenol orange: all of them are G21-'-AO CRESOL GREEN: 29 Ij-'(prepared with ethanol) Edta Standard Solution: 0. Olm

2. The Analytical Method is to take the sample 0.50009 in a 200 ML high-necked beaker. Add 15 ML nitric acid until the sample is dissolved. Remove nitrogen oxide by heating, remove slightly cold, add potassium chlorate 0.59, boil for Zmin, add water to about 150 ml, filter in 250 ml flask. Dilute with water to scale. Absorb 25 ml dry triangle beaker, add 25 ML water. Add barium chloride SML, sodium sulfate 10 ml. Potassium Fluoride 29. Sulphur ignore 10 ml, add one drop of methyl orange indicator. Adjust with hexamethylenetetramine until the solution just disappears. And an excess of 10 mls. Add 3 drops of Cresol green indicator. XYLENOL ORANGE 5 drops. In the amount of. The analytical results of the sample were converted by the standard sample of similar zinc content when Olmol I-EDTA standard solution was titrated to the end point of the solution just turning grass green.

3. The selection of test conditions (l) acidity is known by the acid effect curve. When titrating zinc with EDTA standard solution. The required Ph > Gt; 4. The indicator of xylenol orange was purple-red at Ph > 6.1. Yellow at Ph '6.1. The complex of xylenol orange with metal ion zinc is red. Therefore, the acidity of the solution should be selected under the conditions of 4 & Lt; Ph & Lt; 6.1. The acidity condition of Ph = 5.5 was selected for this method. (2) the effect of potassium chlorate and the amount of research acid is to make the separation of manganese complete. Concentrated nitric acid must be used. Dilute nitric acid should not be used. And don't use too little nitric acid. Otherwise, add potassium chlorate. The solution was found to be spattered. The separation of manganese is incomplete. After testing, 15 ml of concentrated nitric acid was used. Potassium chlorate. () just 59. (3) elimination of interference ions in dry copper alloy lead can be made with Barium chloride containing more than 10 times lead to form barium sulfate mixed crystal precipitation with Sodium Sulfate, which is much less soluble than lead sulfate. Dry Tin, iron, aluminum available potassium fluoride shelter. When the iron, aluminum content is greater than 10,000. It can be masked with 509 l-1'ethylphthalacetone. Copper can be masked by sulphur. (4) the choice of indicator with xylenol orange as indicator. EDTA titration. The change from red to yellow at the end of the solution is not easy to observe. Especially when the titration solution appears lead Barium sulfate precipitation. The end point is even more unobservable. To that end. The mixed indicator of Xylenol orange and cresol green was used when titrated to the end point. There was an obvious jump. That is, the solution changes from purplish red to grass green. The finish line is even more obvious.

4. The results of the analysis are shown in table.

5. Caution when the sample contains more than 20 mg of lead. Barium chloride 10ml must be added, and Barium chloride and sodium sulfate can not be added for samples without lead; potassium fluoride must be added before the sulfur vein, otherwise EF3 + will be reduced to FeZ + by the sulfur suit, and potassium fluoride will lose its masking effect; the boiling time of Zmin must be ensured. Otherwise, the manganese dioxide won't be fully formed for a short time. Source: Chinanews.com, by Ren Yifeng