CN112014384A - Chemical analysis method for accurately measuring copper content in copper or copper additive - Google Patents
Chemical analysis method for accurately measuring copper content in copper or copper additive Download PDFInfo
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Abstract
The invention discloses a chemical analysis method for accurately measuring the copper content in copper or a copper additive, which comprises the following steps: 1) preparing a medicine; 2) preparing and calibrating a standard solution; 3) detecting a copper or copper additive sample; 4) and marking and calculating the result. In the invention, sodium pyrophosphate is used for masking iron and hydroxylamine hydrochloride solution in weak acid solution to eliminate nitrogen oxide; adding excessive potassium iodide solution, reacting copper ions with excessive potassium iodide to generate copper iodide precipitate, and simultaneously separating out quantitative iodine; the amount of copper in the copper or copper additive was determined by titration with a standard solution of sodium thiosulfate using a fresh starch solution as an indicator. The invention can analyze the copper or the copper additive with the copper content more than or equal to 70 percent and can meet the requirement of the inspection of various copper or copper additive products in the industry.
Description
Technical Field
The invention relates to the technical field of chemical analysis, in particular to a chemical analysis method for accurately measuring the copper content in copper or a copper additive, wherein the copper content is more than or equal to 70%.
Background
In the intense market competition, the quality of products is particularly important, the detection requirements of various products are continuously improved, and besides the impurity elements of the detected substances, the direct detection of the purity of the substances is also very important. The method for measuring the chemistry of copper and copper alloy in the national standard at present comprises the following steps: GB/T5121.1-2008 copper and copper alloy chemical analysis methods, wherein, three analysis methods are 1: direct electrolysis-atomic absorption spectrometry; 2. potassium permanganate tellurium oxide-electrolytic atomic absorption spectrometry; 3: the electrolytic spectrophotometry, in which the involved instruments are expensive, is mainly based on the analysis of the content by the instruments, and the detection accuracy is poor due to the high copper content. GB/T5121.1-2008 atomic absorption spectrometry still uses the mixed acid of nitric acid and hydrofluoric acid to dissolve the sample, and is high to the acidproof requirement of utensil, and is big to operating personnel's harm.
In addition, there are some methods for measuring copper content by using iodometry, such as "method for measuring copper content in tin-silver brazing by iodometry" invented by research institute for application of Beijing nonferrous metals and rare earths ", but the harmfulness of strong corrosive acids and irritant acids such as concentrated sulfuric acid and perchloric acid, especially perchloric acid, used for sample pretreatment is greatest.
In terms of the use of the hiding agent, ammonium fluoride and ammonium bifluoride are used as the masking agent of the general iodometry, the two are very harmful and highly corrosive, and after the ammonium fluoride and the ammonium bifluoride are contacted with the skin, fluorine ions are continuously dissociated and permeate into deep tissues to dissolve cell membranes, so that liquefaction and necrosis of epidermis, dermis, subcutaneous tissues and even muscle layers are caused; and the detection range of the copper content by the general iodometry is approximately below 50%.
Disclosure of Invention
The invention aims to solve the technical problems that in the prior art, the detection precision is poor, the requirement on acid resistance of a vessel is high, the harm to operators is large and the like under the conditions of expensive instruments, high copper content and the like, and provides a chemical analysis method for accurately measuring the copper content in copper or a copper additive, wherein the chemical analysis method can be used for quickly and conveniently measuring the copper content in the copper or the copper additive, is low in detection cost, has a low requirement on acid resistance of the vessel, can reduce the harm to the operators and is high in detection precision.
In order to solve the technical problems, the invention adopts the following technical scheme:
a chemical analysis method for accurately measuring the copper content in copper or a copper additive, comprising the steps of:
1) preparing a medicine: nitric acid (1+1), a potassium iodide solution having a concentration of 150g/L, a hydroxylamine hydrochloride solution having a concentration of 100g/L, a potassium thiocyanate solution having a concentration of 100g/L, sodium pyrophosphate solid (AR.), and a fresh starch solution having a concentration of 10g/L were prepared.
2) Preparing and calibrating a standard solution: preparing a 1mol/L sodium thiosulfate standard solution.
Preparing 0.02mol/L sodium thiosulfate standard solution.
Preparing 0.02mol/L copper standard solution.
And (4) calibrating a 0.02mol/L sodium thiosulfate standard solution.
3) Detection of copper or copper additive samples: accurately weighing 0.7 g-0.85 g of copper or copper additive sample in a beaker by using a ten-thousandth balance, adding 40mL of nitric acid (1+1) in the step 1), heating for dissolving, boiling to remove nitrogen oxide after the copper or copper additive sample is completely dissolved, then adding 2g of sodium pyrophosphate solid (AR) in the step 1), cooling after dissolving, filtering to a 250mL volumetric flask, adding distilled water for diluting to 250mL, and then uniformly mixing to obtain a solution A.
10.00mL of the solution A is divided into a conical beaker, 20mL of distilled water, 10mL of the hydroxylamine hydrochloride solution in the step 1) and 10mL of the potassium iodide solution in the step 1) are added, the mixture is placed for 30s, then 0.02mol/L of sodium thiosulfate standard solution which is well-calibrated in the step 2) is used for titration to light yellow, 10mL of the potassium thiocyanate solution in the step 1) and 1mL of the fresh starch solution in the step 1) are added, and the titration to disappearance of blue color is continued by 0.02mol/L of sodium thiosulfate standard solution which is well-calibrated in the step 2).
4) Representation and calculation of the results:
the mass fraction of copper is as follows:
in the formula: c represents the concentration of the sodium thiosulfate standard solution, and the unit is mol/L; v represents the volume of the standard solution of sodium thiosulfate consumed by titration, and the unit is mL; 63.546 is the molar mass of copper in g/mol; m represents the mass of the copper or copper additive sample taken in g.
In one embodiment, the preparation and calibration of the standard solution in step 2) comprises the following steps:
a) preparing a 1mol/L sodium thiosulfate standard solution: weighing 260g of sodium thiosulfate pentahydrate into an erlenmeyer flask, adding a proper amount of boiled water without carbon dioxide for dissolving, adding 10g of anhydrous sodium carbonate, filtering the mixture into a 1L volumetric flask by using cotton after the sodium thiosulfate pentahydrate is completely dissolved, diluting the mixture to 1L by using carbon dioxide-free water, uniformly mixing the mixture to obtain a 1mol/L sodium thiosulfate standard solution, and storing the standard solution for two weeks for use.
b) Preparing 0.02mol/L sodium thiosulfate standard solution: 20mL of the 1mol/L sodium thiosulfate standard solution stored for two weeks in the step a) is filtered into a 1L brown volumetric flask, diluted to 1L with anhydrous carbon dioxide, and then mixed uniformly to obtain 0.02mol/L sodium thiosulfate standard solution.
c) Preparation of 0.02mol/L copper standard solution, namely weighing 1.2709g of pure copper, adding 10mL of nitric acid (1+1) prepared in the step 1), boiling to remove nitrogen oxides, cooling to room temperature, transferring into a 1L volumetric flask, diluting to 1L with distilled water, and mixing uniformly to obtain 0.02mol/L copper standard solution.
d) Calibration of 0.02mol/L sodium thiosulfate standard solution: taking 20.00mL of the 0.02mol/L copper standard solution prepared in the step c), adding 20mL of nitric acid (1+1) in the step 1) into a 250mL conical beaker, heating to remove nitrogen oxides, adding 5g of sodium pyrophosphate solid in the step 1), dissolving and cooling.
And adding 10mL of hydroxylamine hydrochloride solution obtained in the step 1) and 10mL of potassium iodide solution obtained in the step 1) into the conical beaker, standing for 30s, titrating with 0.02mol/L of sodium thiosulfate standard solution prepared in the step b) until the solution in the conical beaker is light yellow, adding 10mL of potassium thiocyanate solution obtained in the step 1) and 2mL of fresh starch solution obtained in the step 1), and continuously titrating until the blue color of the solution in the conical beaker disappears.
The calibration calculation formula of the 0.02mol/L sodium thiosulfate standard solution is as follows:
in the formula: c represents the molar concentration of the copper standard solution and has the unit of mol/L; v represents the volume of the withdrawn copper standard solution in mL; c1 represents the molar concentration of the standard solution of sodium thiosulfate to be calibrated, and the unit is mol/L; v1 represents the volume consumed in mL of the standard solution of sodium thiosulfate to be calibrated for titration.
In one embodiment, the carbon dioxide-free water in step b) is distilled water cooled after boiling for 15 minutes.
The invention has the advantages and beneficial effects that:
1. the invention can analyze the copper or the copper additive with the copper content more than or equal to 70 percent and can meet the requirement of the inspection of various copper or copper additive products in the industry.
2. In the invention, sodium pyrophosphate is used for masking iron and hydroxylamine hydrochloride solution in weak acid solution to eliminate nitrogen oxide; adding excessive potassium iodide solution, reacting copper ions with excessive potassium iodide to generate copper iodide precipitate, and simultaneously separating out quantitative iodine; the amount of copper in the copper or copper additive was determined by titration with a standard solution of sodium thiosulfate using a fresh starch solution as an indicator.
3. The sample pretreatment (i.e. sample dissolution) method of the invention is simple. The existing general sample dissolving method of the iodometric method uses concentrated sulfuric acid, perchloric acid and other strong corrosive acids and irritant acids, and particularly the harmfulness of perchloric acid is the greatest; in GB/T5121.1-2008 atomic absorption spectrometry, a mixed acid of nitric acid and hydrofluoric acid is used for dissolving a sample, and the method only uses nitric acid (1+1), namely dilute nitric acid for dissolving, so that the acid resistance requirement on instruments and the harm to the operation of personnel are reduced greatly.
4. In terms of the use of the masking agent, ammonium fluoride and ammonium bifluoride are used as the masking agent of the existing general iodometry, the two are very harmful and very corrosive, and after the ammonium fluoride and the ammonium bifluoride are contacted with the skin, fluorine ions are continuously dissociated and permeate into deep tissues to dissolve cell membranes, so that liquefaction and necrosis of epidermis, dermis, subcutaneous tissues and muscle layers are caused; the masking agent used in the present invention is sodium pyrophosphate solid, and the harmfulness of the masking agent used in the conventional iodometry is extremely small.
5. In terms of the detection range of copper, the detection range of copper content in the present invention is Cu (%). gtoreq.70% (mass%), whereas the detection range of copper in the ordinary iodometry is approximately below 50%.
6. The invention has strong practicability; the sample has no limitation of objective conditions, can detect the copper or the copper additive, is suitable for the copper or the copper additive used in the electronic industry, the aluminum alloy industry and the like, and has wide application range.
7. The invention has high accuracy. The invention masks the interference of some impurity elements, has good data repeatability, has high accuracy of measured data due to the fact that the method has a large number of sampling amount and good sampling representativeness, and is a chemical analysis method with high accuracy, wherein the relative standard deviation of the measured result reaches 0.06% -0.1% and is 0.12% lower than that of national standard instrument analysis.
8. The invention is simple and convenient to operate. The operation steps involved in the detection method are very simple, and the operation can be independently completed according to the operation steps as long as an operator knows the characters, and the operation can not be performed only by professional training as in analysis of large instruments.
9. The invention has low detection cost. Compared with the prior art, the detection cost of an atomic absorption spectrometer, ICP and an electrolytic spectrophotometry is much lower, and the method conforms to the application and analysis of small and medium-sized enterprises.
Detailed Description
The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
A chemical analysis method for accurately measuring the copper content in copper or a copper additive, comprising the steps of:
1) preparing a medicine: nitric acid (1+ 1): measuring 500mL of distilled water by using a measuring cylinder, adding the distilled water into a beaker with the measuring range of 2000mL, measuring 500mL of pure nitric acid by using the measuring cylinder, adding the measured pure nitric acid into the distilled water while stirring, cooling after uniformly stirring, and finally storing in a brown wide-mouth reagent bottle.
Potassium iodide solution at a concentration of 150 g/L: 150g of analytically pure potassium iodide is weighed, dissolved in distilled water, diluted to 1 liter with distilled water, stored in a brown reagent bottle, and stored in the dark, and is prepared in situ when in use.
100g/L hydroxylamine hydrochloride solution: 100g of analytically pure hydroxylamine hydrochloride are weighed, dissolved in distilled water, diluted to 1 liter with distilled water and stored in brown reagent bottles, ready for use.
100g/L potassium thiocyanate solution: 100g of analytically pure potassium thiocyanate was weighed, dissolved in distilled water, diluted 1 liter with distilled water and stored in a reagent bottle.
Sodium pyrophosphate solid (AR.): sodium pyrophosphate solid (AR.)
10g/L of fresh starch solution: 100mL of distilled water at about 80 ℃ was weighed into a 250mL beaker using a measuring cylinder, 1g of soluble fresh starch (AR.) weighed in advance was added thereto, and the mixture was stirred while being added, boiled again, and then cooled. It is prepared immediately after use.
2) Preparing and calibrating a standard solution: preparing a 1mol/L sodium thiosulfate standard solution.
Preparing 0.02mol/L sodium thiosulfate standard solution.
Preparing 0.02mol/L copper standard solution.
And (4) calibrating a 0.02mol/L sodium thiosulfate standard solution.
3) Detection of copper or copper-added samples: accurately weighing 0.7 g-0.85 g of copper or copper additive sample in a beaker by using a ten-thousandth balance, adding 40mL of nitric acid (1+1) in the step 1), heating for dissolving, boiling to remove nitrogen oxide after the copper or copper additive sample is completely dissolved, then adding 2g of sodium pyrophosphate solid (AR) in the step 1), cooling after dissolving, filtering to a 250mL volumetric flask, adding distilled water for diluting to 250mL, and then uniformly mixing to obtain a solution A.
10.00mL of the solution A is divided into a conical beaker, 20mL of distilled water, 10mL of the hydroxylamine hydrochloride solution in the step 1) and 10mL of the potassium iodide solution in the step 1) are added, the mixture is placed for 30s, then 0.02mol/L of sodium thiosulfate standard solution which is well-calibrated in the step 2) is used for titration to light yellow, 10mL of the potassium thiocyanate solution in the step 1) and 1mL of the fresh starch solution in the step 1) are added, and the titration to disappearance of blue color is continued by 0.02mol/L of sodium thiosulfate standard solution which is well-calibrated in the step 2).
4) Representation and calculation of the results:
the mass fraction of copper is as follows:
in the formula: c represents the concentration of the sodium thiosulfate standard solution, and the unit is mol/L; v represents the volume of the standard solution of sodium thiosulfate consumed by titration, and the unit is mL; 63.546 is the molar mass of copper in g/mol; m represents the mass of the copper or copper additive sample taken in g.
The preparation and calibration of the standard solution in the step 2) comprise the following steps:
a) preparing a 1mol/L sodium thiosulfate standard solution: weighing 260g of sodium thiosulfate pentahydrate into an erlenmeyer flask, adding a proper amount of boiled water without carbon dioxide for dissolving, adding 10g of anhydrous sodium carbonate, filtering the mixture into a 1L volumetric flask by using cotton after the sodium thiosulfate pentahydrate is completely dissolved, diluting the mixture to 1L by using carbon dioxide-free water, uniformly mixing the mixture to obtain a 1mol/L sodium thiosulfate standard solution, and storing the standard solution for two weeks for use. (two weeks before analysis are prepared in advance)
b) Preparing 0.02mol/L sodium thiosulfate standard solution: 20mL of the 1mol/L sodium thiosulfate standard solution stored for two weeks in the step a) were filtered into a 1L brown volumetric flask, diluted to 1L with anhydrous carbon dioxide, and then mixed well.
c) Preparation of 0.02mol/L copper standard solution, weighing 1.2709g of pure copper, adding 10mL of nitric acid (1+1) prepared in the step 1), boiling to remove nitrogen oxides, cooling to room temperature, transferring into a 1L volumetric flask, diluting to 1L with distilled water, and mixing uniformly.
d) Calibration of 0.02mol/L sodium thiosulfate standard solution: taking 20.00mL of the 0.02mol/L copper standard solution prepared in the step c) to a 250mL conical beaker, adding 20mL of nitric acid (1+1) in the step 1), heating to remove nitrogen oxides, adding 5g of sodium pyrophosphate solid (AR) in the step 1), dissolving and cooling.
And adding 10mL of hydroxylamine hydrochloride solution obtained in the step 1) and 10mL of potassium iodide solution obtained in the step 1) into the conical beaker, standing for 30s, titrating with 0.02mol/L of sodium thiosulfate standard solution prepared in the step b) until the solution in the conical beaker is light yellow, adding 10mL of potassium thiocyanate solution obtained in the step 1) and 2mL of fresh starch solution obtained in the step 1), and continuously titrating until the blue color of the solution in the conical beaker disappears.
The calibration calculation formula of the 0.02mol/L sodium thiosulfate standard solution is as follows:
in the formula: c represents the molar concentration of the copper standard solution and has the unit of mol/L; v represents the volume of the withdrawn copper standard solution in mL; c1 represents the molar concentration of the standard solution of sodium thiosulfate to be calibrated, and the unit is mol/L; v1 represents the volume consumed in mL of the standard solution of sodium thiosulfate to be calibrated for titration.
Table 1 below is a table of standard solutions for calibration of 0.02mol/L sodium thiosulfate:
TABLE 1 recording chart for calibrating 0.02mol/L sodium thiosulfate standard solution
Wherein the carbon dioxide-free water in the step b) is distilled water cooled after boiling for 15 minutes.
The principle of the invention is as follows:
in the invention, sodium pyrophosphate solid masking iron and hydroxylamine hydrochloride solution are used to eliminate nitrogen oxides in weak acid solution; adding excessive potassium iodide solution, reacting copper ions with excessive potassium iodide to generate copper iodide precipitate, and simultaneously separating out quantitative iodine; the amount of copper in the copper or copper additive was determined by titration with a standard solution of sodium thiosulfate using a fresh starch solution as an indicator.
The principle of the main chemical reaction is as follows:
2Cu2++4I－＝2CuI↓+I2
I2+2S203 2-＝2I－+S406 2-
CuI+SCN-＝CuSCN↓+I－(Potassium thiocyanate cannot be added too early, otherwise Cu2+ is reduced, and can only be added near the end point, so that the titration reaction proceeds in the forward direction)
Example 1
A chemical analysis method for accurately measuring the copper content in copper or a copper additive, comprising the steps of:
1) preparing a medicine: nitric acid (1+1), a potassium iodide solution having a concentration of 150g/L, a hydroxylamine hydrochloride solution having a concentration of 100g/L, a potassium thiocyanate solution having a concentration of 100g/L, sodium pyrophosphate solid (AR.), and a fresh starch solution having a concentration of 10g/L were prepared.
2) Preparing and calibrating a standard solution:
a) preparing a 1mol/L sodium thiosulfate standard solution: weighing 260g of sodium thiosulfate pentahydrate into an erlenmeyer flask, adding a proper amount of boiled water without carbon dioxide for dissolving, adding 10g of anhydrous sodium carbonate, filtering the mixture into a 1L volumetric flask by using cotton after the sodium thiosulfate pentahydrate is completely dissolved, diluting the mixture to 1L by using carbon dioxide-free water, uniformly mixing the mixture to obtain a 1mol/L sodium thiosulfate standard solution, and storing the standard solution for two weeks for use.
b) Preparing 0.02mol/L sodium thiosulfate standard solution: 20mL of the 1mol/L sodium thiosulfate standard solution stored for two weeks in the step a) were filtered into a 1L brown volumetric flask, diluted to 1L with anhydrous carbon dioxide, and then mixed well. Wherein the carbon dioxide-free water is distilled water cooled after boiling for 15 minutes.
c) Preparation of 0.02mol/L copper standard solution, weighing 1.2709g of pure copper, adding 10mL of nitric acid (1+1) prepared in the step 1), boiling to remove nitrogen oxides, cooling to room temperature, transferring into a 1L volumetric flask, diluting to 1L with distilled water, and mixing uniformly.
d) Calibration of 0.02mol/L sodium thiosulfate standard solution: taking 20.00mL of the 0.02mol/L copper standard solution prepared in the step c) into a 250mL conical beaker, adding 20mL of nitric acid (1+1) in the step 1), heating to remove nitrogen oxides, adding 5g of sodium pyrophosphate solid (AR) in the step 1), dissolving and cooling.
And adding 10mL of hydroxylamine hydrochloride solution obtained in the step 1) and 10mL of potassium iodide solution obtained in the step 1) into the conical beaker, standing for 30s, titrating with 0.02mol/L of sodium thiosulfate standard solution prepared in the step b) until the solution in the conical beaker is light yellow, adding 10mL of potassium thiocyanate solution obtained in the step 1) and 2mL of fresh starch solution obtained in the step 1), and continuously titrating until the blue color of the solution in the conical beaker disappears.
The calibration calculation formula of the 0.02mol/L sodium thiosulfate standard solution is as follows:
in the formula: c represents the molar concentration of the copper standard solution and has the unit of mol/L; v represents the volume of the withdrawn copper standard solution in mL; c1 represents the molar concentration of the standard solution of sodium thiosulfate to be calibrated, and the unit is mol/L; v1 represents the volume consumed in mL of the standard solution of sodium thiosulfate to be calibrated for titration.
Referring to Table 1, which is a table of calibration 0.02mol/L sodium thiosulfate standard solution, the average concentration of the calibration sodium thiosulfate standard solution is 0.01997mol/L as can be seen from Table 1.
3) Detection of copper samples: 0.7036g of copper sample is taken in a beaker, 40mL of nitric acid (1+1) in the step 1) is added, the mixture is heated and dissolved until the copper sample is completely dissolved, then the nitric oxide is boiled to remove completely, 2g of sodium pyrophosphate solid (AR) in the step 1) is added, the mixture is cooled after being dissolved, the mixture is filtered to a volumetric flask with 250mL, distilled water is added to dilute the mixture to 250mL, and then the mixture is uniformly mixed to obtain a solution A.
10.00mL of the solution A is divided into a conical beaker, 20mL of distilled water, 10mL of the hydroxylamine hydrochloride solution in the step 1) and 10mL of the potassium iodide solution in the step 1) are added, the mixture is placed for 30s, then 0.01997mol/L of the standard sodium thiosulfate solution calibrated in the step 2) is used for titration to be light yellow, 10mL of the potassium thiocyanate solution in the step 1) and 1mL of the fresh starch solution in the step 1) are added, the titration with 0.01997mol/L of the standard sodium thiosulfate solution is continued until the blue color disappears, and 22.00mL of the standard sodium thiosulfate solution of 0.01997mol/L is consumed.
4) Representation and calculation of the results:
the mass fraction of copper is as follows:
the principle of the invention is as follows:
in the invention, sodium pyrophosphate solid masking iron and hydroxylamine hydrochloride solution are used to eliminate nitrogen oxides in weak acid solution; adding excessive potassium iodide solution, reacting copper ions with excessive potassium iodide to generate copper iodide precipitate, and simultaneously separating out quantitative iodine; the amount of copper in the copper or copper additive was determined by titration with a standard solution of sodium thiosulfate using a fresh starch solution as an indicator.
The principle of the main chemical reaction is as follows:
2Cu2++4I－＝2CuI↓+I2
I2+2S203 2-＝2I－+S406 2-
CuI+SCN-＝CuSCN↓+I－(Potassium thiocyanate cannot be added too early, otherwise Cu2+ is reduced, and can only be added near the end point, so that the titration reaction proceeds in the forward direction)
Example 2
Example 2 differs from example 1 in that: example 2 a sample of 0.7009 grams of copper was weighed out to consume 21.93mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a mass fraction of copper:
example 3
Example 3 differs from example 1 in that: example 3 a sample of 0.7062 grams of copper was weighed out to consume a total of 22.10mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a mass fraction of copper:
example 4
Example 4 differs from example 1 in that: example 4 a sample of 0.7019 grams of copper was weighed out to consume 22.95mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a mass fraction of copper:
example 5
Example 5 differs from example 1 in that: example 5 a sample of 0.7049 grams of copper was weighed out to consume 22.05mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a mass fraction of copper:
example 6
Example 6 differs from example 1 in that: example 6 a sample of 0.7091 grams of copper was weighed out to consume a total of 22.18mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a mass fraction of copper:
table 2 below shows the results of the analysis of the copper content of the copper samples of examples 1 to 6
TABLE 2 table of the results of the analytical determination of the copper content in the copper samples
As can be seen from Table 2, the detection method of the present invention has good reproducibility as a whole; the relative standard deviation of the detection of the copper sample is 0.0314%, which is 0.12% lower than the relative standard deviation of the international instrumental analysis.
Example 7
A chemical analysis method for accurately measuring the copper content in copper or a copper additive, comprising the steps of:
1) preparing a medicine: nitric acid (1+1), a potassium iodide solution having a concentration of 150g/L, a hydroxylamine hydrochloride solution having a concentration of 100g/L, a potassium thiocyanate solution having a concentration of 100g/L, a sodium pyrophosphate solid, and a fresh starch solution having a concentration of 10g/L were prepared.
2) Preparing and calibrating a standard solution:
a) preparing a 1mol/L sodium thiosulfate standard solution: weighing 260g of sodium thiosulfate pentahydrate into an erlenmeyer flask, adding a proper amount of boiled water without carbon dioxide for dissolving, adding 10g of anhydrous sodium carbonate, filtering the mixture into a 1L volumetric flask by using cotton after the sodium thiosulfate pentahydrate is completely dissolved, diluting the mixture to 1L by using carbon dioxide-free water, uniformly mixing the mixture to obtain a 1mol/L sodium thiosulfate standard solution, and storing the standard solution for two weeks for use.
b) Preparing 0.02mol/L sodium thiosulfate standard solution: 20mL of the 1mol/L sodium thiosulfate standard solution stored for two weeks in the step a) were filtered into a 1L brown volumetric flask, diluted to 1L with anhydrous carbon dioxide, and then mixed well. Wherein the carbon dioxide-free water is cooled after boiling for 15 minutes.
c) Preparation of 0.02mol/L copper standard solution, weighing 1.2709g of pure copper, adding 10mL of nitric acid (1+1) prepared in the step 1), boiling to remove nitrogen oxides, cooling to room temperature, transferring into a 1L volumetric flask, diluting to 1L with distilled water, and mixing uniformly.
d) Calibration of 0.02mol/L sodium thiosulfate standard solution: taking 20.00mL of the 0.02mol/L copper standard solution prepared in the step c) into a 250mL conical beaker, adding 20mL of nitric acid (1+1) in the step 1), heating to remove nitrogen oxides, adding 5g of sodium pyrophosphate solid (AR) in the step 1), dissolving and cooling.
And adding 10mL of hydroxylamine hydrochloride solution obtained in the step 1) and 10mL of potassium iodide solution obtained in the step 1) into the conical beaker, standing for 30s, titrating with 0.02mol/L of sodium thiosulfate standard solution prepared in the step b) until the solution in the conical beaker is light yellow, adding 10mL of potassium thiocyanate solution obtained in the step 1) and 2mL of fresh starch solution obtained in the step 1), and continuously titrating until the blue color of the solution in the conical beaker disappears.
The calibration calculation formula of the 0.02mol/L sodium thiosulfate standard solution is as follows:
in the formula: c represents the molar concentration of the copper standard solution and has the unit of mol/L; v represents the volume of the withdrawn copper standard solution in mL; c1 represents the molar concentration of the standard solution of sodium thiosulfate to be calibrated, and the unit is mol/L; v1 represents the volume consumed in mL of the standard solution of sodium thiosulfate to be calibrated for titration.
Referring to Table 1, which is a table of calibration 0.02mol/L sodium thiosulfate standard solution, the average concentration of the calibration sodium thiosulfate standard solution is 0.01997mol/L as can be seen from Table 1.
3) Detection of copper additive samples: 0.8002g of copper additive sample is taken and placed in a 300mL beaker, 40mL of nitric acid (1+1) in the step 1) is added, the mixture is heated and dissolved, the copper additive sample is completely dissolved, then the nitric oxide is boiled to remove completely, 2g of sodium pyrophosphate solid (AR) in the step 1) is added, the solution is cooled after the dissolution, the solution is filtered to a 250mL volumetric flask, distilled water is added to dilute the solution to 250mL, and then the solution is uniformly mixed to obtain a solution A.
10.00mL of the solution A is divided into a conical beaker, 20mL of distilled water, 10mL of the hydroxylamine hydrochloride solution in the step 1) and 10mL of the potassium iodide solution in the step 1) are added, the mixture is placed for 30s, then 0.01997mol/L of the standard sodium thiosulfate solution calibrated in the step 2) is used for titration to be light yellow, 10mL of the potassium thiocyanate solution in the step 1) and 1mL of the fresh starch solution in the step 1) are added, the titration with 0.01997mol/L of the standard sodium thiosulfate solution is continued until the blue color disappears, and 18.90mL of the standard sodium thiosulfate solution of 0.01997mol/L is consumed.
4) Representation and calculation of the results:
the mass fraction of copper is as follows:
the principle of the invention is as follows:
in the invention, sodium pyrophosphate solid masking iron and hydroxylamine hydrochloride solution are used to eliminate nitrogen oxides in weak acid solution; adding excessive potassium iodide solution, reacting copper ions with excessive potassium iodide to generate copper iodide precipitate, and simultaneously separating out quantitative iodine; the amount of copper in the copper or copper additive was determined by titration with a standard solution of sodium thiosulfate using a fresh starch solution as an indicator.
The principle of the main chemical reaction is as follows:
2Cu2++4I－＝2CuI+I2
I2+2S203 2-＝2I－+S406 2-
CuI+SCN-＝CuSCN↓+I－(Potassium thiocyanate cannot be added too early, otherwise Cu2+ is reduced, and can only be added near the end point, so that the titration reaction proceeds in the forward direction)
Example 8
Example 8 differs from example 7 in that: example 8 a sample of 0.8011 grams of the copper additive was weighed out to consume 18.95mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a copper mass fraction of:
example 9
Example 9 differs from example 7 in that: example 9 a sample of 0.7998 grams of the copper additive was weighed out to consume a total of 18.90mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a mass fraction of copper:
example 10
Example 10 differs from example 7 in that: example 10 a sample of 0.8035 grams of a copper additive was weighed out to consume 19.00mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a copper mass fraction of:
example 11
Example 11 differs from example 7 in that: example 11 a sample of 0.7959 grams of a copper additive was weighed out to consume 18.80mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a copper mass fraction of:
example 12
Example 12 differs from example 7 in that: example 12 a sample of 0.7975 grams of the copper additive was weighed out to consume 18.85mL of 0.01997mol/L standard solution of sodium thiosulfate, resulting in a copper mass fraction of:
table 3 below shows the results of the analytical measurements of the copper contents in the copper additive samples of examples 7 to 12
TABLE 3 table of the results of the analytical determination of the copper content in the copper additive samples
As can be seen from Table 3, the detection method of the present invention has excellent reproducibility as a whole; the relative standard deviation of the test sample of the copper additive was 0.0596%, which is lower than the relative standard deviation of 0.12% for the international instrumental analysis.
The invention has the advantages and beneficial effects that:
1. the invention can analyze the copper or the copper additive with the copper content more than or equal to 70 percent and can meet the requirement of the inspection of various copper or copper additive products in the industry.
2. In the invention, sodium pyrophosphate is used for masking iron and hydroxylamine hydrochloride solution in weak acid solution to eliminate nitrogen oxide; adding excessive potassium iodide solution, reacting copper ions with excessive potassium iodide to generate copper iodide precipitate, and simultaneously separating out quantitative iodine; the amount of copper in the copper or copper additive was determined by titration with a standard solution of sodium thiosulfate using a fresh starch solution as an indicator.
3. The sample pretreatment (i.e. sample dissolution) method of the invention is simple. The existing general sample dissolving method of the iodometric method uses concentrated sulfuric acid, perchloric acid and other strong corrosive acids and irritant acids, and particularly the harmfulness of perchloric acid is the greatest; in GB/T5121.1-2008 atomic absorption spectrometry, a mixed acid of nitric acid and hydrofluoric acid is used for dissolving a sample, and the method only uses nitric acid (1+1), namely dilute nitric acid for dissolving, so that the acid resistance requirement on instruments and the harm to the operation of personnel are reduced greatly.
4. In terms of the use of the masking agent, ammonium fluoride and ammonium bifluoride are used as the masking agent of the existing general iodometry, the two are very harmful and very corrosive, and after the ammonium fluoride and the ammonium bifluoride are contacted with the skin, fluorine ions are continuously dissociated and permeate into deep tissues to dissolve cell membranes, so that liquefaction and necrosis of epidermis, dermis, subcutaneous tissues and muscle layers are caused; the masking agent used in the present invention is sodium pyrophosphate solid, and the harmfulness of the masking agent used in the conventional iodometry is extremely small.
5. In terms of the detection range of copper, the detection range of copper content in the present invention is Cu (%). gtoreq.70% (mass%), whereas the detection range of copper in the ordinary iodometry is approximately below 50%.
6. The invention has strong practicability; the sample has no limitation of objective conditions, can detect the copper or the copper additive, is suitable for the copper or the copper additive used in the electronic industry, the aluminum alloy industry and the like, and has wide application range.
7. The invention has high accuracy. The invention masks the interference of some impurity elements, has good data repeatability, has high accuracy of measured data due to the fact that the method has a large number of sampling amount and good sampling representativeness, and is a chemical analysis method with high accuracy, wherein the relative standard deviation of the measured result reaches 0.06% -0.1% and is 0.12% lower than that of national standard instrument analysis.
8. The invention is simple and convenient to operate. The operation steps involved in the detection method are very simple, and the operation can be independently completed according to the operation steps as long as an operator knows the characters, and the operation can not be performed only by professional training as in analysis of large instruments.
9. The invention has low detection cost. Compared with the prior art, the detection cost of an atomic absorption spectrometer, ICP and an electrolytic spectrophotometry is much lower, and the method conforms to the application and analysis of small and medium-sized enterprises.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (3)
1. A chemical analysis method for accurately measuring the copper content in copper or a copper additive, comprising the steps of:
1) preparing a medicine: preparing nitric acid (1+1), a potassium iodide solution with the concentration of 150g/L, a hydroxylamine hydrochloride solution with the concentration of 100g/L, a potassium thiocyanate solution with the concentration of 100g/L, sodium pyrophosphate solid (AR.), and a fresh starch solution with the concentration of 10 g/L;
2) preparing and calibrating a standard solution: preparing a 1mol/L sodium thiosulfate standard solution;
preparing 0.02mol/L sodium thiosulfate standard solution;
preparing 0.02mol/L copper standard solution;
calibrating a 0.02mol/L sodium thiosulfate standard solution;
3) detection of copper or copper additive samples: accurately weighing 0.7 g-0.85 g of copper or copper additive sample by using a ten-thousandth balance, adding 40mL of nitric acid (1+1) in the step 1), heating for dissolving, boiling to remove nitrogen oxides after the copper or copper additive sample is completely dissolved, adding 2g of sodium pyrophosphate solid (AR) in the step 1), cooling after dissolving, filtering to a 250mL volumetric flask, adding distilled water for diluting to 250mL, and uniformly mixing to obtain a solution A;
dividing 10.00mL of solution A into a conical beaker, adding 20mL of distilled water, 10mL of hydroxylamine hydrochloride solution in the step 1) and 10mL of potassium iodide solution in the step 1), standing for 30s, titrating to light yellow by using 0.02mol/L sodium thiosulfate standard solution which is well calibrated in the step 2), adding 10mL of potassium thiocyanate solution in the step 1) and 1mL of fresh starch solution in the step 1), and continuously titrating to disappear blue by using 0.02mol/L sodium thiosulfate standard solution which is well calibrated in the step 2);
4) representation and calculation of the results:
the mass fraction of copper is as follows:
in the formula: c represents the concentration of the sodium thiosulfate standard solution, and the unit is mol/L; v represents the volume of the standard solution of sodium thiosulfate consumed by titration, and the unit is mL; 63.546 is the molar mass of copper in g/mol; m represents the mass of the copper or copper additive sample taken in g.
2. The chemical analysis method for accurately measuring the copper content in copper or a copper additive according to claim 1, wherein the preparation and calibration of the standard solution in step 2) comprises the following steps:
a) preparing a 1mol/L sodium thiosulfate standard solution: weighing 260g of sodium thiosulfate pentahydrate into an erlenmeyer flask, adding a proper amount of boiled water without carbon dioxide for dissolving, adding 10g of anhydrous sodium carbonate, filtering the mixture into a 1L volumetric flask by using cotton after the sodium thiosulfate pentahydrate is completely dissolved, diluting the mixture to 1L by using carbon dioxide-free water, uniformly mixing the mixture to obtain a 1mol/L sodium thiosulfate standard solution, and storing the standard solution for two weeks for use;
b) preparing 0.02mol/L sodium thiosulfate standard solution: filtering 20mL of the 1mol/L sodium thiosulfate standard solution which is stored for two weeks in the step a) into a 1L brown volumetric flask, diluting the solution to 1L with anhydrous carbon dioxide, and then uniformly mixing to obtain 0.02mol/L sodium thiosulfate standard solution;
c) weighing 1.2709g of pure copper, adding 10mL of nitric acid (1+1) prepared in the step 1), boiling to remove nitrogen oxides, cooling to room temperature, transferring into a 1L volumetric flask, diluting to 1L with distilled water, and mixing uniformly to obtain 0.02mol/L copper standard solution;
d) calibration of 0.02mol/L sodium thiosulfate standard solution: taking 20.00mL of 0.02mol/L copper standard solution prepared in the step c) to a 250mL conical beaker, adding 20mL of nitric acid (1+1) in the step 1), heating to remove nitrogen oxides, adding 5g of sodium pyrophosphate solid (AR) in the step 1), dissolving and cooling;
adding 10mL of hydroxylamine hydrochloride solution obtained in the step 1) and 10mL of potassium iodide solution obtained in the step 1) into the conical beaker, standing for 30s, titrating the solution by using 0.02mol/L sodium thiosulfate standard solution prepared in the step b) until the solution in the conical beaker is light yellow, adding 10mL of potassium thiocyanate solution obtained in the step 1) and 2mL of fresh starch solution obtained in the step 1), and continuously titrating until the blue color of the solution in the conical beaker disappears;
the calibration calculation formula of the 0.02mol/L sodium thiosulfate standard solution is as follows:
in the formula: c represents the molar concentration of the copper standard solution and has the unit of mol/L; v represents the volume of the withdrawn copper standard solution in mL; c1 represents the molar concentration of the standard solution of sodium thiosulfate to be calibrated, and the unit is mol/L; v1 represents the volume consumed in mL of the standard solution of sodium thiosulfate to be calibrated for titration.
3. The chemical analysis method for accurately measuring the copper content in copper or a copper additive according to claim 2, wherein the carbon dioxide-free water in step b) is distilled water cooled after boiling for 15 minutes.
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