Method for rapidly detecting concentration of industrial concentrated acid based on neutralization reaction

Abstract

The invention relates to the field of chemical analysis and detection, in particular to a method for rapidly detecting the concentration of industrial concentrated acid based on neutralization reaction, which comprises the following steps: 1, theoretical calculation; converting molar concentration according to acid density and mass fraction; 2, accurately measuring the volume of target acid by using a pipette; 2, injecting 100-150ml of pure water into the triangular flask, and adding 3-5 drops of phenolphthalein; 3, slowly injecting an acid sample into the triangular flask, and slightly shaking and uniformly mixing; 4, adding 10.00 ml of NaOH solution by using the pipette, and oscillating for 10-20 seconds; 3, result interpretation: transparency and colorless: acid is excessive when the acid concentration reaches the standard, pH is less than or equal to 8.2 after neutralization, pink lasts for 20-30 seconds, and reinspection is needed when the acid concentration is insufficient and the pH is greater than or equal to 8.3. The method has the beneficial effects that 1, a reverse judgment method is adopted, namely the conventional end-point titration is replaced by fixed alkali amount, so that the detection time is shortened to 2 minutes; 2, safety design: pre-dilution reduces the risk of acid mist, and only a trace amount of raw acid is needed to avoid acid corrosion; 3, multi-acid adaptation: compatibility with detection of different types of concentrated acids is realized through pipetting volume adjustment;

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical analysis and detection, and particularly relates to a method for rapidly detecting concentration of industrial concentrated acid based on neutralization reaction. BACKGROUND

[0002] Industrial acid concentration control is crucial to production process. Traditional acid-base titration method needs to be titrated to endpoint successively, which is time-consuming and requires professional operation. In view of the rapid quality inspection demand of nitric acid, hydrofluoric acid and hydrochloric acid, a simple and intuitive detection scheme is urgently needed.

[0003] The present application optimizes the detection precision of concentrated acid on the basis of the original chemical analysis and detection method, and is suitable for rapid detection of industrial field under different environmental temperatures. By presetting the corresponding relationship between acid concentration and theoretical sodium hydroxide consumption, the sodium hydroxide addition volume is fixed (10 ml), and the color of phenolphthalein is used to reversely judge whether the acid concentration meets the standard: transparent and colorless: the actual concentration of acid is greater than or equal to the nominal value (acid excess); pink color does not fade: acid concentration is insufficient (alkali excess). SUMMARY

[0004] The purpose of the present application is to provide a method for rapidly detecting the concentration of industrial concentrated acid based on neutralization reaction.

[0005] The purpose of the present application is achieved by the method for rapidly detecting the concentration of industrial concentrated acid based on neutralization reaction, which comprises the following steps: step one: theoretical calculation; converting molar concentration according to acid density and mass fraction:

[0006] 60% nitric acid ρ=1.367 g / ml:

[0007]

[0008] Theoretical neutralization volume: V NaOH =13.0170×V HNO3 ÷1000V HNO3 =0.768 ml, V NaOH =10 ml, M NaOH =1 mol / L (theoretical molar concentration of sodium hydroxide, actual concentration needs to be calibrated)

[0009] Similarly, we have:

[0010] 55% hydrofluoric acid (ρ=1.18 g / ml): the amount to be removed is 0.310 ml, 31% hydrochloric acid (ρ=1.16 g / ml): the amount to be removed is 1.005 ml;

[0011] Step two: operation process: 1. Accurately measure the volume of the target acid, i.e. 0.768ml of nitric acid, 0.310ml of hydrofluoric acid and 1.005ml of hydrochloric acid with a pipette, 2. Pour 100-150ml of pure water into a triangular flask, add 3-5 drops of phenolphthalein, 3. Slowly pour the acid sample into the triangular flask, mix well by shaking, 4. Add 10.00ml of NaOH solution with a pipette, shake for 10-20 seconds;

[0012] Step three: result interpretation: transparent and colorless: the acid concentration meets the standard, i.e. the acid is excessive, the pH after neutralization is ≤8.2, the pink color lasts for 20-30 seconds: the acid concentration is insufficient, i.e. the pH is ≥8.3, which needs to be rechecked.

[0013] If the temperature of the detection solvent is not room temperature, temperature compensation is required, i.e. the acid solution and the NaOH solution are placed in the detection environment for 10-15 minutes before operation.

[0014] The beneficial effects of the present application are: 1. Reverse determination method: by fixing the alkali amount instead of traditional end-point titration, the detection time is shortened to 2 minutes; 2. Safety design: pre-dilution reduces the risk of acid mist, only a small amount of original acid is needed to avoid acid corrosion; 3. Multi-acid adaptation: compatible with different types of concentrated acid detection by adjusting the volume of the pipette. DETAILED DESCRIPTION

[0015] 1. Core principle: by pre-setting the corresponding relationship between acid concentration and theoretical sodium hydroxide consumption, the sodium hydroxide addition volume is fixed (10ml), and the phenolphthalein color development is used to reversely judge whether the acid concentration meets the standard: transparent and colorless: the actual acid concentration is ≥ the nominal value (acid excess); pink color does not fade: acid concentration is insufficient (alkali excess).

[0016] 2. Reagent composition: calibrated NaOH solution (1.0000mol / L±0.1%), phenolphthalein indicator (1% ethanol solution), calibrated pipette (accuracy ±0.01ml), triangular flask (250ml)

[0017] Technical scheme: step 1: theoretical calculation: according to the acid density and mass fraction, the molar concentration is converted (example): 60% nitric acid (ρ=1.367g / ml):

[0018]

[0019] Theoretical neutralization volume: V NaOH =V NaOH =13.0170×V HNO3 ÷1000

[0020] V HNO3 =0.768ml, (V NaOH =10ml).

[0021] Similarly, for 55% hydrofluoric acid (ρ = 1.18 g / ml): 0.310 ml needs to be transferred, and for 31% hydrochloric acid (ρ = 1.16 g / ml): 1.005 ml needs to be transferred.

[0022] Step 2: Operating Procedure: 1. Accurately measure the target acid volume (0.768 ml nitric acid, 0.310 ml hydrofluoric acid, 1.005 ml hydrochloric acid) using a pipette; 2. Pour 150 ml of pure water into the Erlenmeyer flask and add 3 drops of phenolphthalein; 3. Slowly pour the acid sample into the Erlenmeyer flask and gently shake to mix; 4. Quickly add 10.00 ml of NaOH solution using a pipette and shake for 10 seconds.

[0023] Step 3: Result interpretation: Transparent and colorless: acid concentration meets the standard (excess acid, pH ≤ 8.2 after neutralization); Pink color lasting for 30 seconds: acid concentration is insufficient (pH ≥ 8.3, retesting is required).

[0024] 1. Reverse determination method: By replacing traditional endpoint titration with a fixed amount of alkali, the detection time is shortened to 2 minutes. 2. Safety design: Pre-dilution reduces the risk of acid mist; only a trace amount of original acid is needed to avoid acid corrosion. 3. Multi-acid compatibility: Compatible with the detection of different types of concentrated acids by adjusting the pipetting volume.

[0025] Instance data verification

[0026] Acid Type Nominal Concentration Measured Concentration Color Result Nitric Acid 60％ 62％ Colorless Hydrofluoric Acid 55％ 53％ Pink Hydrochloric Acid 31％ 30.5％ Pink

[0027] New temperature compensation: To address the impact of temperature on the accuracy of solution volume and density, dynamic correction is achieved through the following strategies: 1. Acid density temperature correction: The acid density changes with temperature, and the following formulas are introduced for correction: Nitric acid: density ρT=ρ20-0.0011×(T-20)(g / ml), hydrofluoric acid: density ρT=ρ20-0.0009×(T-20)(g / ml), hydrochloric acid: density ρT=ρ20-0.0012×(T-20)(g / ml).

[0028] 2. Effect of NaOH solution concentration on temperature: Record the temperature when calibrating NaOH. If the temperature difference is >5℃, recalibrate according to CT=C20÷[1+0.0002×(T-20)].

[0029] Step 1: Theoretical calculation (with added temperature compensation): 1. Measure the ambient temperature (T) and correct the acid density and transfer volume according to the above formula.

[0030] 2. Example (25℃ environment): 60% nitric acid: ρT = 1.367 - 0.0011 × 5 = 1.3615 g / ml;

[0031]

[0032] (Comparative original 0.763 ml, volume increased 0.013 ml after temperature compensation)

[0033] Step 2: Operation flow optimization: Add a step before operation: Place the acid solution and NaOH solution in the detection environment for 15 minutes.

[0034] Step 3: Color result interpretation expansion: High temperature environment (> 30℃): Phenolphthalein color change may be delayed, and observation should be extended to 30 seconds; Low temperature environment (< 10℃): Solution viscosity increases, and preheating of the pipette tip is recommended.

[0035] Example revision (temperature influence verification)

[0036] Temperature Acid Type Nominal Concentration Uncompensated Result Compensated Result 15℃ Nitric Acid 60％ Pink (False Positive) Colorless (Correct) 28℃ Hydrochloric Acid 31％ Colorless (False Positive) Pink (Correct)

[0037] Industrial application value improvement: 1. Temperature adaptability: Maintain detection error < 2% in 10-40℃ environment. 2. Compatibility enhancement: Adapt to complex environments such as high-latitude low-temperature factories and tropical area workshops. Through the above improvements, this patent significantly improves the detection results while ensuring easy operation, meeting the stringent needs of industrial applications.

[0038] This method is suitable for raw material acceptance and process monitoring in chemical plants and steel pickling lines, with a single detection cost of less than 0.5 yuan, and an efficiency improvement of 80% compared to traditional methods.

[0039] Example 1

[0040] Operation and results: Accurately pipette 0.310 hydrofluoric acid into a triangular flask containing 150 ml of pure water + 3 drops of phenolphthalein (ice water bath maintained at 12℃), add 10.00 ml of NaOH (20℃ calibration) and shake, phenomenon: The solution is transparent and colorless (determined concentration ≥55%), verification: The actual concentration measured by laboratory titration method is 55.8%, with an error <1.5%.

[0041] Example 2

[0042] 31% hydrochloric acid detection in high temperature environment (32℃): Operation conditions: Environment temperature: 32℃, use preheated pipette (32℃ constant temperature) to pipette 1.005 ml of hydrochloric acid; inject into a triangular flask containing 150 ml of warm water (32℃) + 3 drops of phenolphthalein; add 10.00 ml of NaOH and shake, observe after 20-30 seconds; Phenomenon: Pink color does not fade (determined concentration <31%); Verification: The actual concentration measured by laboratory titration method is 30.2%, which is consistent with the result.

[0043] The above only describes specific embodiments of the present application, but the structural features of the scope of protection of the present application are not limited thereto, and any changes or modifications made by those skilled in the art within the scope of the present application are covered by the patent scope of the present application.

Claims

1. A method for rapid detection of concentration of industrial concentrated acid based on neutralization reaction, characterized in that: Comprising the following steps: Step one: theoretical calculation; according to the acid density and mass fraction to convert molar concentration: 60% nitric acid ρ=1.367g / ml: Theoretical neutralization and volume: V NaOH = 13.0170 x V HNO3 ÷ 1000 V HNO3 = 0.768 ml, V NaOH = 10 ml, M NaOH = 1 mol / L, theoretical molar concentration of sodium hydroxide, actual concentration needs to be calibrated; Similarly: 55% hydrofluoric acid (ρ=1.18g / ml): the amount of 0.310ml needs to be removed, 31% hydrochloric acid (ρ=1.16g / ml): the amount of 1.005ml needs to be removed; Step two: operation process:

1. Accurately measure the target acid volume with a pipette, that is, 0.768ml of nitric acid, 0.310ml of hydrofluoric acid, and 1.005ml of hydrochloric acid, 2. Pour 100-150ml of pure water into a triangular flask, add 3-5 drops of phenolphthalein, 3. Slowly pour the acid sample into the triangular flask, mix well, 4. Add 10.00ml of NaOH solution with a pipette, shake for 10-20 seconds; Step three: result interpretation: transparent and colorless: the acid concentration meets the standard, that is, the acid is excessive, the pH after neutralization is ≤8.2, pink color lasts for 20-30 seconds: the acid concentration is insufficient, that is, the pH is ≥8.3, recheck is needed.

2. The method for rapid detection of concentration of industrial concentrated acid based on neutralization reaction according to claim 1, characterized in that: If the detection solvent temperature is not room temperature, temperature compensation is needed, that is, the acid liquid and NaOH solution are placed in the detection environment for 10-15 minutes before operation.

Images