1. A SPECTROMETRIC DETERMINATION OF CALCIUM IN A WATER SAMPLE
1.1 Objective
UTo uUse a the calibration-line method of the calibration line andto determine the concentration of calcium ions in a water sample. Express Express tThe results are expressed in mmol/L and mg/L.
1.2 Background
Calcium ions form a complex with o-cresolphtalein complexon. The solution of a the complex is violet.
1.3 Equipment and reagents
- A Spectrometer SpektraTM spectrometer.
- A cColour- forming reagent for determining the concentrationation of calcium.
- A sStandard solution of CaCl2.
Hazards
/ The cColour- forming reagent contains 8-hydroxyquinoline which, causeswhich causes skin irritation., Aavoid contact with skin contact.R: 22-36/37/38, S: 26-36/37
1.4 Procedure
For the blank, all five calibration solutions and the sample, follow the procedure as given below.
Blank / Standard / SampleDeionised water / 40 l / / / /
Standard solution of cCalcium chloride standard solution / / / 40 l / /
Sample / / / / / 40 l
Colour- forming reagent / 300 l / 300 l / 300 l
Mix thoroughly, measure after five minutes at the green LED.
Write the measurements in a the table below and calculate the absorbance.
Ca2+ [mg/L] / 10 / 32 / 54 / 76 / 98 / SampleT [%]
A
Calculation of the result:
Calculate the calibration- line equation and the mass concentration of calcium in a the water sample. You This can be done easily do this inwith MS Excel by drawing, if you draw a scatter plot. The mMass concentration of calcium ions is an independent variable and the absorbance is a dependent variable. After drawing a the graph, select the option “Add trend line” and then the option “Show equation in a graph”. Next,Now you insert the sample absorbance in the equation as y, and then calculate x, which represents the mass concentration of calcium ions in a the water sample. TExpress the final result should also be expressed as an amount concentration. Write both results in a the table “Results – Major Components”, under the serial number of your the sample.
= 40.08 g/mol
2. A SPECTROMETRIC DETERMINATION OF HYDROGEN PHOSPHATE IN A WATER SAMPLE
2.1 Objective
UUse a one-point calibration and determine the concentration of hydrogen phosphate in a water sample.
2.2 Background
cationic dye
malachite green
HPO42 + 12 MoO42 + 23 H+ PMo12O403 + 12 H2O green coloration
2.3 Equipment and reagents
- A Spectrometer SpektraTM spectrometer.
- A cColour- forming reagent for determining the concentrationation of hydrogen phosphate.
- A sStandard solution of Na2HPO4.
Hazards
/ The cColour- forming reagent contains sulphuric acid, which is corrosive and causes skin burns., Cwhile continued contact can cause tissue necrosis.R: 35, S: 26-30-45
2.4 Procedure
For the blank, the standard and the sample, follow the procedure as given below.
Blank / Standard / SampleDeionised water / 8 / / / /
Standard solution of disodium hydrogen phosphate / / / 8 / /
Sample / / / / / 8
Colour- forming reagent / 1 / 1 / 1
Mix thoroughly, measure after twenty minutes at the red LED.
Write the measurements in a the table below and calculate the absorbance.
T [%] / A / [mg/L]Standard / 0.5
Sample
Calculation of the result:
Calculate the concentration of hydrogen phosphate ions in a the sample and write the result in the table “Results – Contaminants”, under the serial number of the sampleunder your sample number.
The mMaximumal admissible allowed concentration of phosphate in drinking water is 0.3 mg/L.
3. A SPECTROMETRIC DETERMINATION OF CHLORIDE IN A WATER SAMPLE
3.1 Objective
UUse a one-point calibration and determine the concentration of chloride ions in a water sample. Express Express the results the result in mmol/L and mg/L.
3.2 Background
Hg(SCN)2 + 2 Cl HgCl2 + 2 SCN
SCN + Fe3+ Fe(SCN)2
orange-brown coloration
3.3 Equipment and reagents
- A Spectrometer SpektraTM spectrometer.
- A cColour- forming reagent for determining the concentrationation of chloride.
- A sStandard solution of NaCl.
Hazards
/ Ethylene glycol monomethyl ether, (2-Methoxyethanol) is a flammable liquide.R: 60-61-10-20/21/22.1, S: 53.1-45
/ Mercury(II) thiocyanate is toxic. R and repeated exposure may can cause damage to the liver, the kidneys and the central nervous system damage.
R: 26/27/28-32-33, S: 13-28-36-45
/ Nitric acid isacid is corrosive. A, avoid skin contact and inhalation.
R: 8-35, S: 23-26-36-45
3.4 Procedure
For the blank, the standard and the sample, follow the procedure as given below.
Blank / Standard / SampleDeionised water / 6 / / / /
Standard solution of sSodium chloride standard solution / / / 6 / /
Sample / / / / / 6
Colour- forming reagent / 3 / 3 / 3
Mix thoroughly, measure after five minutes at the blue LED.
Write the measurements in a the table below and calculate the absorbance.
T [%] / A / [mmol/L] / [mg/L]Standard / 0.200
Sample
Calculation of the result:
Calculate the amount and the mass concentration of chloride ions in a the water sample. Write the results in a the table “Results –- Major Components”, under the serial number of the sampleunder your sample number.
= 35.45 g/mol
The mMaximumal admissible allowed concentration for of chloride in drinking water is 100 mg/L.
4. A SPECTROMETRIC DETERMINATION OF AMMONIUM IONS IN A WATER SAMPLE
4.1 Objective
UUse a one- point calibration and determine the concentration of ammonium ions in a water sample.
4.2 Background
NH4+ + OH NH3 + H2O
NH3 + OCl NH2Cl + OH
Na2[Fe(CN)5NO]
HO + NH2Cl O N Cl
O N Cl + OH O N OH
Indophenol (blue coloration)
4.3 Equipment and reagents
- A SpektraTM sSpectrometer SpektraTM .
- A pPhenolic reagent.
- A bBasic solution of chlorate(I) - hypochlorite.
- A sStandard solution of NH4Cl.
Hazards
/ Phenol isPhenol is corrosive and toxic: it cc. Causes severe irritation of the upper respiratory tract and is h. Harmful if absorbed through the skin. Avoid inhalation and skin contact.R: 24/25-34, S: 28.2-45
/ Phenolic reagent contains sodium nitroprusside dihydrate (sodium nitroferricyanide(III) dihydrate). This canMay cause respiratory- tract and skin irritation. Avoid contact.
R: 26/27/28-32, S: 7-28-29-45
/ Sodium hypochlorite causeshypochlorite causes chemical burns to the respiratory tract. May It can also cause skin burns, and when. iIn contact with acids it liberates toxic gases.
R: 31-34, S: 28-45-50.1
/ Sodium hydroxide causeshydroxide causes skin burns. May It can also cause a skin rash (in milder cases), and cold and clammy skin with cyanosis or a pale colour.
R: 35, S: 26-37/39-45
4.4 Procedure
For the blank, the standard and the sample, follow the procedure as given below.
Blank / Standard / SampleDeionised water / 1 / / / /
Ammonium chloride standard Ssolution / / / 1 / /
Sample / / / / / 1
Phenolic reagent / 4 / 4 / 4
Mix thoroughly.
Hypochlorite solution / 4 / 4 / 4
Mix thoroughly, measure after thirty minutes at the red LED.
Write the measurements in a the table blow and calculate the absorbance.
T [%] / A / [mg/L]Standard / 0.5
Sample
Calculation of the results:
Calculate the final result and enter it under your the serial number of the sample number in a the table “Results – Contaminants”.
The mMaximumal admissible allowed concentration for of ammonium ions in drinking water is 0.1 mg/L.
5. A COLORIMETRIC DETERMINATION OF NITRITE IN A WATER SAMPLE
5.1 Objective
EEstimate the concentration of nitrite ions in a water sample. Perform a the procedure as indicated below and compare the final coloration of the examined solution with the coloration for of the three standards, with which have nitrite concentrations of 0.01 mg/L, 0.1 mg/L and 0.5 mg/L.
5.2 Background
HO3S NH2 + NO2 + 2 H+ HO3S N+ N + 2 H2O
HO3S N+ N + NH2 HO3S N N NH2
Red coloration
+ H+
5.3 Equipment and reagents
- A sSolution of sulfanilic acid.
- A sSolution of 1-naphthylamine
- An aAcetate buffer solution of pH 3.03, concentration 1.58 mol/L.
- Three standard solutions of NaNO2 with different concentrations.
Hazards
/ Sulfanilic acid (4-aminobenzenesulfonic acid ) causes skin and respiratory- tract irritation. It can, may also cause an allergic reaction.R 36/38-43, S 24-37
/ 1-naphthylamine may can effect the central nervous system.
R: 45-22-51/53, S: 53-24-45-61
/ Acetic acid isacid is corrosive. Prolonged or repeated skin contact may can cause dermatitis.
R: 10-35, S: 23-26-45
5.4 Procedure
For the blank, all three standards and the sample, follow the procedure as given below.
Blank / Standard / SampleDeionised water / 4 / / / /
Standard solution of nitrite / / / 4 / /
Sample / / / / / 4
Sulfanilic acid / 1 / 1 / 1
Mix thoroughly, wait five minutes.
1-naftilamin / 1 / 1 / 1
Buffer solution / 3 / 3 / 3
Mix thoroughly, after ten minutes estimate the concentration of nitrite ions in the sample solution.
Write the result of your the estimation in a the table “Results – -Contaminants”, under your the serial number of the sample number.
The mMaximumal admissible allowed concentration for of nitrite in drinking water is 0.1 mg/L.
Note:
If you prefer to do the experiment with a spectrometer, use the nitrite standard with the highest concentration for the one- point calibration. Measure after 10 minutes, use the green LED.
T [%] / A / [mg/L]Standard / 0.5
Sample
6. A TITRIMETRIC DETERMINATION OF HYDROGEN CARBONATE CONCENTRATION IN A WATER SAMPLE
6.1 Objective
UUse a miniaturised and simplified acidimetric titration and to determine the concentration of hydrogen carbonate in a water sample. Use a syringe instead of a burette, and use a Coulter- counter container as a replacement for an Erlenmeyer flask.
6.2 Background
Write a the reaction on which the titration is based.
6.3 Equipment and reagents
- A dDevice for miniaturized titration.
- A sStandard solution of hydrochloric acid, concentration 0.1 mol/L.
- A sSolution of bromochresol green (Phenol, 4,4'-(3H-1,2-benzoxathiol-3-ylidene)bis[2,6-dibromo-3- methyl-, S,S-dioxide) indicator.
Hazards
/ Hydrochloric acid is corrosive. A, avoid inhalation or contact with skin contact.R: 34-37, S: 26-45
6.4 Procedure
1. Fill a the syringe with a the standard solution of HCl.
2. Fill a the Coulter- counter container with the water sample up to the first mark (V=10 ml) with a water sample.
3. Add a drop of a the bromocresol green indicator solution to the sample.
4. Titrate the examined solution until its colour changes to pale green. Be careful, the solution must not turn yellowish-green.
5. From a syringe readRecord a the volume of the HCl solution consumed for during the titration from the syringe.
Note.
It willThe procedure can be made be easier for you if youby first estimatinge approximate the volume of HCl standard solution that , which is needed to reach the end- point of ta he titration. Start with a preliminary titration in which theyou add HCl solution is added in 0.05- ml increments.
Calculation of the result:
Calculate the amount and the mass concentration of hydrogen carbonate in a the water sample.
= 61.00 g/mol
Write both results in a the table “Results – Major components”, under your the serial number of the sample number.
7. A TITRIMETRIC DETERMINATION OF THE TOTAL CONCENTRATION OF CALCIUM AND MAGNESIUM IONS IN A WATER SAMPLE – TOTAL WATER HARDNESS
7.1 Objective
UUse a complexometric titration and to determine the total concentration of calcium and magnesium ions in a water sample. The titration is simplified and miniaturised. Use a syringe instead of a burette, and use a Coulter-counter container as a replacement for an Erlenmeyer flask.A syringe is in a function of a burette, an Erlenmeyer flask is replaced with a Coulter counter container.
7.2 Background
Write a the reaction of calcium and magnesium ions with a solution of disodium salt of EDTA. For the latter use a the simplified expression Na2H2Y.
7.3 Equipment and reagents
- A dDevice for miniaturized titration.
- A sStandard solution of disodium salt of EDTA (N,N'-1,2-Ethanediylbis[N-(carboxymethyl)glycine],
disodium salt, dihydrate ), concentration 0.1 mol/L.
- A sSolution of ammonium buffer, pH 10, concentration 19.8 mol/L.
- A mMixture of Eriochrome black T and NaCl.
Hazards
/ The aAmmonia solution - care should be taken in handled carefullymanipulating the solution duebecause of to the unpleasant smell of the gas, which causes irritation of the eyes and skin.R: 36/37/38, S 26-36/37/39-45-61
7.4 Procedure
1. Fill a the syringe with a the standard solution of EDTA.
2. Fill a the Coulter- counter container with the water sample up to the first mark (V=10 ml) with a water sample.
3. Add Five five drops of the pH- 10 buffer solution and a spatula of the mixture of indicator Eriochrome black T ain nd NaCl.
4. Titrate the examined solution carefully until you just obtain the moment when the final blue coloration of the solution is obtained.
5. Read aRecord the volume of the EDTA solution consumed for during the titration from a the syringe.
Note.
The procedure can be made easier by first estimating the volume of standard solution that is needed to reach the end-point of the titration. It will be easier for you if you firs estimate approximate volume of standard solution, which is needed to reach the end point of a titration. Start with a preliminary titration in which you add the standard solution of disodium salt of EDTA is added in 0.05- ml increments.
Calculation of the result:
Calculate the total amount concentration of calcium and magnesium ions in a the water sample.
Find a the result of the spectrometric determination of calcium in a the water sample. Calculate the amount and mass concentration of the magnesium ions in a the water sample.
= 24.31 g/mol
Write all requested the results in a the table “Results – Major Components”, under your the serial number of the sample number.
8. A POTENTIOMETRIC DETERMINATI’ON OF THE pH OF A WATER SAMPLE pH
8.1 Objective
UUse a two- point calibration and determine the pH of a water sample. Register the asymmetric potential and the slope of theof the pH electrode.
8.2 Background
The measuring system for the a potentiometric determination of pH consists of: a mV-meter with the a high input resistance (> 1 TΩ), a combined pH electrode with a glass membrane, a temperature sensor and the examined solution. In the combined electrode, a glass electrode and a reference electrode of the Ag-AgCl type are assembled in the same body.
The relation between the electrode potential and the activity of the H3O+ ions in a solution is defined by the Nernst equation. For practical use the relation can be written as follows:
E = k + s·log[H3O+]orE = k – s·pH
where the lLetter s stands for the slope. The theoretical slope at standard temperature is 0.0592 V. The pH-meter is built so that at the a pH of 7.00 the potential should be 0.0 mV. However, rReal electrodes seldom perform ideally, and. aAs a consequence the pH-meter should be calibrated before use. At least a two-point calibration should be used; this involves, in which two calibration buffers for which the pH is reliably known at the working temperature are used. The calibration process provides, gives us anthe insight into the asymmetric potential, and the real slope, or the real relative slope, of the electrode in use. The aAsymmetric potential gives provides information about, how much the potential at pH 7.00 differs from the expected zero potential.
The calibration lays the foundation forensures the reliability of the pH determination in of the examined solution. But However, it is important that the pH of examined solutions must not exceedfalls within the range of the calibration and their that the temperature must beis very close to that at which the calibration was performed.
8.3 Equipment and reagents
- A Portable pH meter WTW pH 323/325 portable pH-meter.
- A cCalibration buffer of pH 4.
- A cCalibration buffer of pH 10.
8.4 Procedure
Calibration of a the pH-meter
The electrode glass membrane is very sensitive and can break easily. Use a polymeric beaker as a drain while rinsing the electrode. Rinse the electrode membrane with deionised water between measurements. Dry the membrane gently with tissue paper.
Use the calibration buffers pH 4 in and pH 10 calibration buffers for the calibration procedure. Mix the buffer solution thoroughly before use. Immerse the electrode with a clean and dry membrane in the first buffer solution.
Repeatedly pPress the button CAL button so manyuntil times the, that ASY calibration mode appearss on the screen of the pH- meter. ThenNext, press the button RUN button. Wait until the pH value stabilises. Use the appropriate arrow button and set the correct pH for the selected buffer at the working temperature. Confirm the setting with the button RUN button. Register the asymmetric potential and the temperature.
Rinse and dry the surface of the electrode membrane and then immerse the electrode in another buffer solution. Press Repeatedly press the button RUN button so many times that you access the possibilityuntil it is possible to input the pH again. Wait until the pH value stabilises and then set the correct pH value as previouslybefore. Confirm with the RUN button RUN. Register the slope of the electrode. Clean and dry the electrode membrane.
Determining the pH of the wWater samplee pH determination
Immerse the clean and dry electrode membrane into the sample solution. Select pH measurement by pressing the button pH/mV, and then confirm the selection with the button RUN button. Wait until the pH stabilises. Write the pH of a the water sample and the other requested data into the table below.
Asymmetric potential / Slope / pH Also Writewrite the pH also in the table “»FundamentalBasic data on water samples”«, under the serial number of tyour he sample.
9. A DETERMINATION OF THE CCONDUCTIVITY OF A WATER SAMPLE AND AN ESTIMATION OF THE TOTAL DISSOLVED SOLIDS (TDS)
9.1 Objective
DDetermine the electrical conductivity of a water sample and estimate the total dissolved solids (TDS).
9.2 Background
The mMeasuring system consists of a conductometric probe with an incorporated temperature sensor (4) and a portable conductivity -meter. The conductometric probe is represented illustrated in the picture below. A pair of voltaic (2) and electric current (3 – ring shape) electrodes is clearly marked.
Vstaviti sliko !!!
Conductivity is the reciprocal of resistance. The measuring unit is Siemens (S), which equals 1/Ω. Measuring The measurement results are expressed in S/cm at the reference temperature; this, what makes the results obtained with probes of different geometriesy and at under different conditions comparable.
A dDetermination of a solution’s conductivity is theprovides a first indication of the concentration of electrolytes dissolved in the sample solution. The term, total dissolved solids (TDS), is used in water analysis. A hHigher conductivity of water relatesis related to a higher concentration of TDS in the water.
TDS = f · conductivity
For natural waters the proportional factor f is expected to be in the range between 0.55– and 0.76, and dependings on the type of a water sample. The selected proportional factor is already in the memory of the conductivity meter;, therefore, the amount of TDS is readable directly from the screen of the conductivity- meter.
Note. A mMeasurement of the a solution’s conductivity gives only an estimation of the TDS. The exact value of for the TDS is obtained from a complete analysis of a water sample, as a, and is the sum of the mass concentrations of all the anions, cations and weaek electrolytes, but not gassesgases, expressed in mg/L.
9.3 Equipment and reagents
- A WTW LF 323/325 Portable portable conductivity -meter WTW LF 323/325.
9.4 Procedure
Press the button κ button to select the measurement of conductivity ( µS/cm). Immerse the conductometric probe in the sample solution. Start the measurement by pressing the button RUN button. Press the κ button κ to access the TDS reading. Rinse and dry the probe after the measuring process.
Conductivity / TDS (mg/L) Under your the serial number of the sample number write the conductivity and the TDS in the table “«FundamentalBasic data on water samples”«.