CN104459022A - Method for determining content of sodium chloride in hexamethylene 1, 6-disodium dithiosulfate dihydrate - Google Patents

Abstract

The invention discloses a method for determining the content of sodium chloride in hexamethylene 1, 6-disodium dithiosulfate dihydrate, relates to a method for determining the content of sodium chloride in HTS, and aims to solve the problem of high errors of the existing method for determining the content of sodium chloride in HTS. The method comprises the following steps of firstly, preparing a solution, namely, preparing NaCl standard solution, preparing AgNO3 solution, preparing NH4SCN solution, and preparing an ammonium ferric sulfate indicator; secondly, calibrating the NH4SCN solution; and thirdly, titrating an HTS specimen. The method is mainly used for determining the content of sodium chloride in hexamethylene 1, 6-disodium dithiosulfate dehydrate.

Description

The assay method of sodium chloride content in hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate

Technical field

The present invention relates to the assay method of sodium chloride content in a kind of HTS

Background technology

Hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate, chemical formula is C ₆h ₁₆o ₈s ₄na ₂, molecular structural formula is hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate is as a kind of after cure stabilizing agent of excellent performance in rubber industry, and a small amount of interpolation can make rubber form cross-linked structure thus effectively improve the serviceable life of rubber.On domestic and international market, general called after Duralink HTS sells, usual referred to as HTS in the world.

The reaction equation of the industrial synthesis of HTS is:

2Na ₂S ₂O ₃+Cl-(CH ₂) ₆-Cl→NaO ₃SS-(CH ₂) ₆-SSO ₃Na+2NaCl

In HTS, a certain amount of sodium chloride as impurity is had by reaction equation is known.If be blended in, if sodium chloride in HTS is excessive will badly influence the quality of rubber.Therefore the content of sodium chloride as impurity is the important indicator evaluating product quality.

What current most enterprises adopted usually when measuring sodium chloride content in HTS is Mohr method, namely with AgNO ₃titration Cl ^-, generate AgCl precipitation.K during titration end-point ₂crO ₄indicator and silver ion react and generate brick-red Ag ₂crO ₄precipitation.This method finds that titration error is comparatively large in practice, analyzes its reason mainly:

(1) sodium thiosulfate of excessive interpolation during a small amount of synthesis is usually mixed with in HTS.There is a series of reaction in sodium thiosulfate and silver ion, final silver oxide and the sulphur generating black.The amount of silver nitrate is consumed bigger than normal during titration, and the judgement of color when the silver oxide of black affects terminal.Usually the method dripping hydrogen peroxide during Mohr method titration chlorion eliminates the interference of sodium thiosulfate, but infeasible here.Infeasible reason is that hydrogen peroxide and HTS also can react, and cannot ensure that the product that HTS and hydrogen peroxide react does not react with silver ion on the one hand, cannot ensure that sodium thiosulfate is eliminated clean on the other hand.

(2) can there is the material that certain reaction generates instability in HTS and silver ion, causes the consumption of silver nitrate during titration excessive.

Summary of the invention

The present invention seeks to solve sodium chloride content method in existing mensuration HTS and there is the large problem of error, and provide hexa-methylene 1, the assay method of sodium chloride content in 6-bisthiosulfate disodium salt dihydrate.

In hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate, the assay method of sodium chloride content completes according to the following steps:

One, solution preparation: 1., prepare NaCl standard solution: be dissolved in by sodium chloride in distilled water, adopts volumetric flask to carry out constant volume, namely obtains the NaCl standard solution that concentration is 0.05mol/L; 2., AgNO is prepared ₃solution: by AgNO ₃be dissolved in distilled water, adopt brown volumetric flask to carry out constant volume, namely obtain the AgNO that concentration is 0.1mol/L ₃solution; 3., NH is prepared ₄sCN solution: by NH ₄sCN is dissolved in distilled water, adopts volumetric flask to carry out constant volume, namely obtains NH ₄sCN solution; 4., preparation ammonium ferric sulfate indicator: first add nitric acid to distilled water, then add NH ₄fe (SO ₄) ₂12H ₂o, is stirred to NH ₄fe (SO ₄) ₂12H ₂o dissolves completely, and namely obtain the ammonium ferric sulfate indicator that massfraction is D, described distilled water and the volume ratio of nitric acid are 10:1, and the massfraction of described nitric acid is 65%;

Two, NH is demarcated ₄sCN solution:

1., in 100mL conical flask, add the NaCl standard solution that 5mL concentration is 0.05mol/L, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 4, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution is 2 DEG C/min with heating rate is 70 DEG C from room temperature to temperature, and heats 20min at temperature is 70 DEG C, then be cooled to room temperature, add 2mL glycerine, shake up, and ensure that pH value of solution is 1 ~ 4, add the ammonium ferric sulfate indicator that 1mL massfraction is D, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₁;

1. can be obtained by step 2: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{mL}+C_{N{H}_4\mathrm{SCN}}\×V_1---\left(1\right)$

In formula (1) represent the concentration of liquor argenti nitratis ophthalmicus, C _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption;

2., in 100mL conical flask, the AgNO that 5mL concentration is 0.1mol/L is added ₃solution, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 3, be 4 DEG C/min is 70 DEG C from room temperature to temperature with heating rate, and heats 20min at temperature is 70 DEG C, then room temperature is cooled to, add 2mL glycerine, shake up, and ensure that pH value of solution is 1 ~ 4, add the ammonium ferric sulfate indicator that 1mL massfraction is D, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₂;

2. can be obtained by step 2: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{N{H}_4\mathrm{SCN}}\×V_2---\left(2\right)$

In formula (2) represent the concentration of liquor argenti nitratis ophthalmicus, represent the concentration of ammonium thiocyanate solution, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

3., can be obtained by formula (1) and formula (2): $C_{{\mathrm{NH}}_4\mathrm{SCN}}=\frac{C_{\mathrm{NaCl}}\×5}{V_2-V_1}---\left(3\right)$

C in formula (3) _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

Three, titration HTS sample:

By M g hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate is dissolved in distilled water, the volumetric flask of 250mL is adopted to carry out constant volume, obtain HTS sample, the HTS sample of 5mL is added in 100mL conical flask, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 3, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution, with heating rate be 3 DEG C/min from room temperature to backflow, and back flow reaction is to solution becomes clear, colorless by muddiness, adds 1mL glycerine, shakes up, and ensures that pH value of solution is 1 ~ 4, adds the ammonium ferric sulfate indicator that 1mL massfraction is D, uses NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₃;

Can obtain: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{mL}+C_{N{H}_4\mathrm{SCN}}\×V_3---\left(4\right)$

C in formula (4) _naClrepresent the concentration of NaCl in HTS sample, represent the concentration of ammonium thiocyanate solution, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, represent the concentration of liquor argenti nitratis ophthalmicus;

$\frac{m_{\mathrm{NaCl}}}{M_{\mathrm{NaCl}}}=C_{\mathrm{NaCl}}\×5\mathrm{mL}---\left(5\right)$

C in formula (5) _naClrepresent the concentration of NaCl in HTS sample, m _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M _naClrepresent the relative molecular mass of NaCl, M _naCl=58.44;

$w_{\mathrm{NaCl}}=\frac{m_{\mathrm{NaCl}}}{M_1}\×100\%---\left(6\right)$

M in formula (6) _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M ₁represent the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 5mL in step 3, w _naClrepresent the massfraction of sodium chloride;

$M_1=M\×\frac{5}{250}---\left(7\right)$

M in formula (6) ₁represent hexa-methylene 1 in the HTS sample of 5mL in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, M is hexa-methylene 1 in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of i.e. 250mL;

Can be obtained by formula (3), formula (4) formula (5) formula (6) and formula (7):

$w_{\mathrm{NaCl}}=\frac{5\×58.44\×0.1\×(V_2-V_1-V_3)\×M\×5}{250\×(V_2-V_1)}\×100\%---\left(8\right)$

Carry out abbreviation to formula (8) can be calculated:

$w_{\mathrm{NaCl}}=\frac{58.44\×(V_2-V_1-V_3)\×M}{100\×(V_2-V_1)}\×100\%---\left(9\right)$

W in formula (9) _naClrepresent the massfraction of sodium chloride, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, M is the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in step 3, i.e. the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 250mL.

Advantage of the present invention: the present invention solves sodium chloride content method in existing mensuration HTS and there is error greatly, and detection method is simple, and the relative standard deviation of measurement result is less than 0.36, and testing result is accurate, and measurement result reappearance is better.

Embodiment

Embodiment one: present embodiment is the assay method of sodium chloride content in hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate, specifically completes according to the following steps:

One, solution preparation: 1., prepare NaCl standard solution: be dissolved in by sodium chloride in distilled water, adopts volumetric flask to carry out constant volume, namely obtains the NaCl standard solution that concentration is 0.05mol/L; 2., AgNO is prepared ₃solution: by AgNO ₃be dissolved in distilled water, adopt brown volumetric flask to carry out constant volume, namely obtain the AgNO that concentration is 0.1mol/L ₃solution; 3., NH is prepared ₄sCN solution: by NH ₄sCN is dissolved in distilled water, adopts volumetric flask to carry out constant volume, namely obtains NH ₄sCN solution; 4., preparation ammonium ferric sulfate indicator: first add nitric acid to distilled water, then add NH ₄fe (SO ₄) ₂12H ₂o, is stirred to NH ₄fe (SO ₄) ₂12H ₂o dissolves completely, and namely obtain the ammonium ferric sulfate indicator that massfraction is D, described distilled water and the volume ratio of nitric acid are 10:1, and the massfraction of described nitric acid is 65%;

Two, NH is demarcated ₄sCN solution:

1., in 100mL conical flask, add the NaCl standard solution that 5mL concentration is 0.05mol/L, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 4, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution is 2 DEG C/min with heating rate is 70 DEG C from room temperature to temperature, and heats 20min at temperature is 70 DEG C, then be cooled to room temperature, add 2mL glycerine, shake up, and ensure that pH value of solution is 1 ~ 4, add the ammonium ferric sulfate indicator that 1mL massfraction is D, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₁;

1. can be obtained by step 2: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{mL}+C_{N{H}_4\mathrm{SCN}}\×V_1---\left(1\right)$

In formula (1) represent the concentration of liquor argenti nitratis ophthalmicus, C _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption;

2., in 100mL conical flask, the AgNO that 5mL concentration is 0.1mol/L is added ₃solution, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 3, be 4 DEG C/min is 70 DEG C from room temperature to temperature with heating rate, and heats 20min at temperature is 70 DEG C, then room temperature is cooled to, add 2mL glycerine, shake up, and ensure that pH value of solution is 1 ~ 4, add the ammonium ferric sulfate indicator that 1mL massfraction is D, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₂;

2. can be obtained by step 2: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{N{H}_4\mathrm{SCN}}\×V_2---\left(2\right)$

In formula (2) represent the concentration of liquor argenti nitratis ophthalmicus, represent the concentration of ammonium thiocyanate solution, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

3., can be obtained by formula (1) and formula (2): $C_{{\mathrm{NH}}_4\mathrm{SCN}}=\frac{C_{\mathrm{NaCl}}\×5}{V_2-V_1}---\left(3\right)$

C in formula (3) _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

Three, titration HTS sample:

By M g hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate is dissolved in distilled water, the volumetric flask of 250mL is adopted to carry out constant volume, obtain HTS sample, the HTS sample of 5mL is added in 100mL conical flask, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 3, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution, with heating rate be 3 DEG C/min from room temperature to backflow, and back flow reaction is to solution becomes clear, colorless by muddiness, adds 1mL glycerine, shakes up, and ensures that pH value of solution is 1 ~ 4, adds the ammonium ferric sulfate indicator that 1mL massfraction is D, uses NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₃;

Can obtain: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{mL}+C_{N{H}_4\mathrm{SCN}}\×V_3---\left(4\right)$

C in formula (4) _naClrepresent the concentration of NaCl in HTS sample, represent the concentration of ammonium thiocyanate solution, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, represent the concentration of liquor argenti nitratis ophthalmicus;

$\frac{m_{\mathrm{NaCl}}}{M_{\mathrm{NaCl}}}=C_{\mathrm{NaCl}}\×5\mathrm{mL}---\left(5\right)$

C in formula (5) _naClrepresent the concentration of NaCl in HTS sample, m _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M _naClrepresent the relative molecular mass of NaCl, M _naCl=58.44;

$w_{\mathrm{NaCl}}=\frac{m_{\mathrm{NaCl}}}{M_1}\×100\%---\left(6\right)$

M in formula (6) _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M ₁represent the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 5mL in step 3, w _naClrepresent the massfraction of sodium chloride;

$M_1=M\×\frac{5}{250}---\left(7\right)$

M in formula (6) ₁represent hexa-methylene 1 in the HTS sample of 5mL in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, M is hexa-methylene 1 in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of i.e. 250mL;

Can be obtained by formula (3), formula (4) formula (5) formula (6) and formula (7):

$w_{\mathrm{NaCl}}=\frac{5\×58.44\×0.1\×(V_2-V_1-V_3)\×M\×5}{250\×(V_2-V_1)}\×100\%---\left(8\right)$

Carry out abbreviation to formula (8) can be calculated:

$w_{\mathrm{NaCl}}=\frac{58.44\×(V_2-V_1-V_3)\×M}{100\×(V_2-V_1)}\×100\%---\left(9\right)$

W in formula (9) _naClrepresent the massfraction of sodium chloride, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, M is the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in step 3, i.e. the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 250mL.

Experimental principle

By the HTS testing sample (hexa-methylene 1 containing sodium chloride and thiosulfuric acid sodium impurity, 6-bisthiosulfate disodium salt dihydrate) in acid condition (pH is 1 ~ 4), adding excessive liquor argenti nitratis ophthalmicus, take ammonium ferric sulfate as indicator.With the remaining silver nitrate of ammonium thiocyanate solution titration of concentration known.SCN during titration end-point ^-with Fe ³⁺generate pale red complex.Drop reaction and indicator reaction as follows:

Excessive silver ion: Ag ⁺+ Cl ^-→ AgCl ↓ (white) K _sp=1.8 × 10 ^-10

Drop reaction: Ag ⁺+ SCN ^-→ AgSCN ↓ (white) K _sp=1.0 × 10 ^-12

Titration end-point: Fe ³⁺+ SCN ^-→ FeSCN ²⁺(redness) K ₁=138

Titration is carried out mainly in order to allow Fe under pH is the condition of 1 ~ 4 ³⁺with lilac [Fe (H ₂o) ₆] ³⁺form exist, the color now observed in solution is almost colourless, and titration end-point judges obvious.More in addition, the S in HTS ₂o ₃ ^2-there is decomposition reaction in acid condition:

S ₂O ₃ ^2-+2H ⁺→SO ₂+S+H ₂O

S ₂o ₃ ^2-be decomposed into sulphur and sulphuric dioxide in acid condition, can not react with silver ion, therefore can not disturb titration.

Following hydrolysis reaction may be there is under HTS acid condition:

O ₃S ₂(CH ₂) ₆S ₂O ₃ ^2-+2H ₂O→HS ₂(CH ₂) ₆SH+2HSO ₄ ^-

Hydrolysis reaction under HTS acid condition and H ⁺concentration is relevant with temperature, H ⁺concentration is larger, more high reaction rate is faster for temperature.HTS and HTS hydrolysate HS ₂(CH ₂) ₆sH likely reacts with silver ion interference titration, and whether interference exists to need experimental analysis to verify.

In operating process after adding excess nitric acid silver, with heating rate be 3 DEG C/min ~ 4 DEG C/min, from room temperature to fluidized state (temperature is 70 DEG C), after cooling, use ammonium thiocyanate titration again.Heat effect:

(1) by SCN excessive in the known titration process of solubility product constant of silver chloride and silver thiocyanate _-can displacement reaction be there is with silver chloride, generate the AgSCN that solubleness is less.Therefore during titration end-point, solution redness can fade away, and cause ammonium thiocyanate consumption excessive, titration end-point is delayed.Heating liquid to be measured can make AgCl precipitate effective coagulation, reduces the generation that silver nitride precipitation transforms.A small amount of glycerine is added after solution cooling ^[5], make the AgCl precipitation surface of generation cover one deck organic solvent, thus avoid contacting with external solution, the conversion of AgCl precipitation during the titration end-point that can effectively slow down further.

(2) chlorion that silver nitride precipitation adsorbs can be made in heating process fully to dissociate to produce silver nitride precipitation, reduce titration error.

(3) sodium thiosulfate is decomposed into sulphur and sulphuric dioxide in acid condition.But in fact there is the dense of the acid of this reaction needed, decompose not exclusively under normal temperature.Undecomposed sodium thiosulfate and silver ion react the black silver sulfide generated and precipitate.Heat and boil a period of time can ensure black silver sulfide precipitation decomposition discharge silver ion, thus eliminate interference.

(4) heating can make HTS be hydrolyzed rapidly, and after boiling a period of time, hydrolysis completely, and hydrolysate can not react with silver ion in acid condition and generate insoluble substance, and solution becomes water white transparency, is conducive to the judgement of titration end-point.

Embodiment two: the difference of present embodiment and embodiment one is: step one is 4. middle prepares ammonium ferric sulfate indicator: first add nitric acid to distilled water, then add NH ₄fe (SO ₄) ₂12H ₂o, is stirred to NH ₄fe (SO ₄) ₂12H ₂o dissolves completely, and namely obtain the ammonium ferric sulfate indicator that massfraction is 10%, described distilled water and the volume ratio of sulfuric acid are 10:1, and the massfraction of described nitric acid is 65%.Other are identical with embodiment one.

Adopt following verification experimental verification effect of the present invention

Test one: the assay method of sodium chloride content in hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate, specifically completes according to the following steps:

One, solution preparation: 1., prepare NaCl standard solution: be dissolved in by sodium chloride in distilled water, adopts volumetric flask to carry out constant volume, namely obtains the NaCl standard solution that concentration is 0.05mol/L; 2., AgNO is prepared ₃solution: by AgNO ₃be dissolved in distilled water, adopt brown volumetric flask to carry out constant volume, namely obtain the AgNO that concentration is 0.1mol/L ₃solution; 3., NH is prepared ₄sCN solution: by NH ₄sCN is dissolved in distilled water, adopts volumetric flask to carry out constant volume, namely obtains NH ₄sCN solution; 4., preparation ammonium ferric sulfate indicator: first add nitric acid to distilled water, then add NH ₄fe (SO ₄) ₂12H ₂o, is stirred to NH ₄fe (SO ₄) ₂12H ₂o dissolves completely, and namely obtain the ammonium ferric sulfate indicator that massfraction is 10%, described distilled water and the volume ratio of sulfuric acid are 10:1, and the massfraction of described nitric acid is 65%;

Two, NH is demarcated ₄sCN solution:

1., in 100mL conical flask, add the NaCl standard solution that 5mL concentration is 0.05mol/L, add the salpeter solution that massfraction is 65%, pH is adjusted to 1.4, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution is 4 DEG C/min with heating rate is 70 DEG C from room temperature to temperature, and heats 20min at temperature is 70 DEG C, then be cooled to room temperature, add 2mL glycerine, shake up, and ensure that pH value of solution is 1.2, add the ammonium ferric sulfate indicator that 1mL massfraction is 10%, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₁;

1. can be obtained by step 2: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{mL}+C_{N{H}_4\mathrm{SCN}}\×V_1---\left(1\right)$

In formula (1) represent the concentration of liquor argenti nitratis ophthalmicus, C _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption;

2., in 100mL conical flask, the AgNO that 5mL concentration is 0.1mol/L is added ₃solution, add the salpeter solution that massfraction is 65%, pH is adjusted to 1.5, be 4 DEG C/min is 70 DEG C from room temperature to temperature with heating rate, and heats 20min at temperature is 70 DEG C, then room temperature is cooled to, add 2mL glycerine, shake up, and ensure that pH value of solution is 2, add the ammonium ferric sulfate indicator that 1mL massfraction is 10%, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₂;

2. can be obtained by step 2: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{N{H}_4\mathrm{SCN}}\×V_2---\left(2\right)$

In formula (2) represent the concentration of liquor argenti nitratis ophthalmicus, represent the concentration of ammonium thiocyanate solution, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

3., can be obtained by formula (1) and formula (2): $C_{{\mathrm{NH}}_4\mathrm{SCN}}=\frac{C_{\mathrm{NaCl}}\×5}{V_2-V_1}---\left(3\right)$

C in formula (3) _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

Three, titration HTS sample:

By M g hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate is dissolved in distilled water, the volumetric flask of 250mL is adopted to carry out constant volume, obtain HTS sample, the HTS sample of 5mL is added in 100mL conical flask, add the salpeter solution that massfraction is 65%, pH is adjusted to 1.4, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution, with heating rate be 3 DEG C/min from room temperature to backflow, and back flow reaction is to solution becomes clear, colorless by muddiness, add 1mL glycerine, shake up, and ensure that pH value of solution is 1.2, add the ammonium ferric sulfate indicator that 1mL massfraction is 10%, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₃;

Can obtain: $C_{{\mathrm{AgNO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{mL}+C_{N{H}_4\mathrm{SCN}}\×V_3---\left(4\right)$

C in formula (4) _naClrepresent the concentration of NaCl in HTS sample, represent the concentration of ammonium thiocyanate solution, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, represent the concentration of liquor argenti nitratis ophthalmicus;

$\frac{m_{\mathrm{NaCl}}}{M_{\mathrm{NaCl}}}=C_{\mathrm{NaCl}}\×5\mathrm{mL}---\left(5\right)$

C in formula (5) _naClrepresent the concentration of NaCl in HTS sample, m _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M _naClrepresent the relative molecular mass of NaCl, M _naCl=58.44;

$w_{\mathrm{NaCl}}=\frac{m_{\mathrm{NaCl}}}{M_1}\×100\%---\left(6\right)$

M in formula (6) _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M ₁represent the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 5mL in step 3, w _naClrepresent the massfraction of sodium chloride;

$M_1=M\×\frac{5}{250}---\left(7\right)$

M in formula (6) ₁represent hexa-methylene 1 in the HTS sample of 5mL in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, M is hexa-methylene 1 in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of i.e. 250mL;

Can be obtained by formula (3), formula (4) formula (5) formula (6) and formula (7):

$w_{\mathrm{NaCl}}=\frac{5\×58.44\×0.1\×(V_2-V_1-V_3)\×M\×5}{250\×(V_2-V_1)}\×100\%---\left(8\right)$

Carry out abbreviation to formula (8) can be calculated:

$w_{\mathrm{NaCl}}=\frac{58.44\×(V_2-V_1-V_3)\×M}{100\×(V_2-V_1)}\×100\%---\left(9\right)$

W in formula (9) _naClrepresent the massfraction of sodium chloride, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, M is the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in step 3, i.e. the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 250mL.

Through calculating known NH ₄sCN solution concentration is 0.02629mol/L.

Get each parallel titration of different amount five times respectively to the HTS sample that this test procedure three obtains, calculate relative standard deviation and sodium chloride content, result is as shown in table 1.

Table 1

As can be seen from Table 1, the relative standard deviation of measurement result is less than 0.36, measurement result reappearance is better, and the sodium chloride content obtained when getting different quantitative determination is close, and the present invention illustrates that the interference of solution to be measured sodium thiosulfate and HTS after treatment is eliminated.

Claims (2)

1. the assay method of sodium chloride content in hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate, is characterized in that the assay method of sodium chloride content in hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate completes according to the following steps:

One, solution preparation: 1., prepare NaCl standard solution: be dissolved in by sodium chloride in distilled water, adopts volumetric flask to carry out constant volume, namely obtains the NaCl standard solution that concentration is 0.05mol/L; 2., AgNO is prepared ₃solution: by AgNO ₃be dissolved in distilled water, adopt brown volumetric flask to carry out constant volume, namely obtain the AgNO that concentration is 0.1mol/L ₃solution; 3., NH is prepared ₄sCN solution: by NH ₄sCN is dissolved in distilled water, adopts volumetric flask to carry out constant volume, namely obtains NH ₄sCN solution; 4., preparation ammonium ferric sulfate indicator: first add nitric acid to distilled water, then add NH ₄fe (SO ₄) ₂12H ₂o, is stirred to NH ₄fe (SO ₄) ₂12H ₂o dissolves completely, and namely obtain the ammonium ferric sulfate indicator that massfraction is D, described distilled water and the volume ratio of nitric acid are 10:1, and the massfraction of described nitric acid is 65%;

Two, NH is demarcated ₄sCN solution:

1., in 100mL conical flask, add the NaCl standard solution that 5mL concentration is 0.05mol/L, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 4, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution is 2 DEG C/min with heating rate is 70 DEG C from room temperature to temperature, and heats 20min at temperature is 70 DEG C, then be cooled to room temperature, add 2mL glycerine, shake up, and ensure that pH value of solution is 1 ~ 4, add the ammonium ferric sulfate indicator that 1mL massfraction is D, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₁;

1. can be obtained by step 2: $C_{\mathrm{Ag}{\mathrm{NO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{ML}+C_{{\mathrm{NH}}_4\mathrm{SCM}}\×V_1---\left(1\right)$

In formula (1) represent the concentration of liquor argenti nitratis ophthalmicus, C _naClrepresent the concentration of sodium chloride standard solution, represent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption;

2., in 100mL conical flask, the AgNO that 5mL concentration is 0.1mol/L is added ₃solution, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 3, be 4 DEG C/min is 70 DEG C from room temperature to temperature with heating rate, and heats 20min at temperature is 70 DEG C, then room temperature is cooled to, add 2mL glycerine, shake up, and ensure that pH value of solution is 1 ~ 4, add the ammonium ferric sulfate indicator that 1mL massfraction is D, use NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₂;

2. can be obtained by step 2: $C_{\mathrm{Ag}{\mathrm{NO}}_3}\×5\mathrm{mL}=C_{{\mathrm{NH}}_4\mathrm{SCN}}\×V_2---\left(2\right)$

In formula (2) represent the concentration of liquor argenti nitratis ophthalmicus, represent the concentration of ammonium thiocyanate solution, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

3., can be obtained by formula (1) and formula (2): $C_{{\mathrm{NH}}_4\mathrm{SCN}}=\frac{C_{\mathrm{NaCl}}\×5}{V_2-V_1}---\left(3\right)$

C in formula (3) _naClrepresent the concentration of sodium chloride standard solution, C _nH4SCNrepresent the concentration of ammonium thiocyanate solution, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption;

Three, titration HTS sample:

By M g hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate is dissolved in distilled water, the volumetric flask of 250mL is adopted to carry out constant volume, obtain HTS sample, the HTS sample of 5mL is added in 100mL conical flask, add the salpeter solution that massfraction is 65%, pH is adjusted to 1 ~ 3, then add the AgNO that 5mL concentration is 0.1mol/L ₃solution, with heating rate be 3 DEG C/min from room temperature to backflow, and back flow reaction is to solution becomes clear, colorless by muddiness, adds 1mL glycerine, shakes up, and ensures that pH value of solution is 1 ~ 4, adds the ammonium ferric sulfate indicator that 1mL massfraction is D, uses NH ₄the titration of SCN solution, to there is stable pale red, keep violent shake in titration process, parallel titration three times, averages, record NH ₄the volume V of SCN solution consumption ₃;

Can obtain: $C_{\mathrm{Ag}{\mathrm{NO}}_3}\×5\mathrm{mL}=C_{\mathrm{NaCl}}\×5\mathrm{ML}+C_{{\mathrm{NH}}_4\mathrm{SCM}}\×V_3---\left(4\right)$

C in formula (4) _naClrepresent the concentration of NaCl in HTS sample, represent the concentration of ammonium thiocyanate solution, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, represent the concentration of liquor argenti nitratis ophthalmicus;

$\frac{m_{\mathrm{NaCl}}}{M_{\mathrm{NaCl}}}=C_{\mathrm{NaCl}}\×5\mathrm{mL}---\left(5\right)$

C in formula (5) _naClrepresent the concentration of NaCl in HTS sample, m _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M _naClrepresent the relative molecular mass of NaCl, M _naCl=58.44;

$w_{\mathrm{NaCl}}=\frac{m_{\mathrm{NaCl}}}{M_1}\×100\%---\left(6\right)$

M in formula (6) _naClrepresent the quality of NaCl in the HTS sample of 5mL in step 3, M ₁represent the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 5mL in step 3, w _naClrepresent the massfraction of sodium chloride;

$M_1=M\×\frac{5}{250}---\left(7\right)$

M in formula (6) ₁represent hexa-methylene 1 in the HTS sample of 5mL in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, M is hexa-methylene 1 in step 3, the quality of 6-bisthiosulfate disodium salt dihydrate, the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of i.e. 250mL;

Can be obtained by formula (3), formula (4) formula (5) formula (6) and formula (7):

$w_{\mathrm{NaCl}}=\frac{5\×58.44\×0.1\×(V_2-V_1-V_3)\×M\×5}{250\×(V_2-V_1)}\×100\%---\left(8\right)$

Carry out abbreviation to formula (8) can be calculated:

$w_{\mathrm{NaCl}}=\frac{58.44\×(V_2-V_1-V_3)\×M}{100\×(V_2-V_1)}\×100\%---\left(9\right)$

W in formula (9) _naClrepresent the massfraction of sodium chloride, V ₁represent step 2 1. middle NH ₄the volume of SCN solution consumption, V ₂represent step 2 2. middle NH ₄the volume of SCN solution consumption, V ₃represent NH in step 3 ₄the volume of SCN solution consumption, M is the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in step 3, i.e. the quality of hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate in the HTS sample of 250mL.

2. the assay method of sodium chloride content in hexa-methylene 1,6-bisthiosulfate disodium salt dihydrate according to claim 1, is characterized in that preparation ammonium ferric sulfate indicator during step one 4.: first add nitric acid to distilled water, then add NH ₄fe (SO ₄) ₂12H ₂o, is stirred to NH ₄fe (SO ₄) ₂12H ₂o dissolves completely, and namely obtain the ammonium ferric sulfate indicator that massfraction is 10%, described distilled water and the volume ratio of sulfuric acid are 10:1, and the massfraction of described nitric acid is 65%.