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Saturday, November 7, 2020

AutoCAD 2020

Information Civil

 AUTO CAD 2020

How to install AutoCAD 2020 :

AutoCAD official full version available on Autodesk's official website. You can download the AutoCAD file from Autodesk official website, and buy the licence from Autodesk by paying a sufficient amount. 

Or you can download the AutoCAD student version from Autodesk's official website by providing genuine document to Autodesk.

AutoCAD 2020 Title

But you can Download Install and Activate full version of Autodesk AutoCAD 2020 lifetime for FREE.

For Install AutoCAD 2020 Full version you have to follow some important steps. You have to watch complete video guide to Install AutoCAD 2020 for FREE.

SYSTEM REQUIREMENTS :

  • Software Name-  AutoCAD 2020
  • Operating System- Windows 7/8/8.1/10
  • Compatibility Architecture:  64 Bit (x64)
  • Developers : Autodesk

Step-1- Download AutoCAD 2020 file from given link- AUTOCAD 2020

Step-2- Watch complete video guide- How to install AutoCAD 2020 for free

Password for AUTOCAD 2020 file- estiakahmed.xyz

Watch YouTube channel - Civil Design

AutoCAD handbook  -      Book for Beginners

                                            Book for Advanced

If  you have 32 bit operating system, then this above file may not support to your system. You can download AutoCAD 2009 and install the same file to your system. 

To download the file, Click here-  AutoCAD 2009








Wednesday, October 7, 2020

Vane shear test

Information Civil

 Vane Shear Test

A major problem of shear strength is the structural strength of soil. The undrained shear strength of a soft clay is measured by the vane shear test. The vane shear test usually provides accurate result for soils of low strength as less than 0.3 kg/cm2, which is not possible in unconfined compressive test or Triaxial test.  The vane shear test of soil is quite cheaper and quicker method of determination of shear strength of soft clay. Therefore the vane shear test usually conducted in laboratory as well as field.

Vane shear title image


The undrained shear strength of soft clay is determined by Vane shear test. The vane shear test as follows-

APPARATUS :-

  • Vane shear apparatus
  • Soil specimen container
  • vernier callipers

PROCEDURE :-

  1. Firstly prepare a couple of  specimen for multiple observation of Vane shear test. Make the specimen for Vane shear test of 37.5 mm diameter and 75 mm of height, which stated as the L/D ratio 2 or 3/
  2. Place the specimen to the vane shear container for vane shear test. and place the container to the base of vane shear apparatus.
  3. Gently lower the vane shear needle as the top of the vane should be 10 mm below the top of the sample, without disturbing the specimen.
  4. Now take the initial reading of the graduated ring provided the upper portion of the vane shear apparatus.
  5. Apply the torque by rotate the vane at a uniform speed of  0.1o/s, until the specimen fails/
  6. Note the final reading of the graduated ring as the angle of twist.

OBSERVATION :-


Vane shear table image




Vane shear formula image



PRECAUTIONS :-

  • Set accurately the spring to the vane shear apparatus for the vane shear test. And note down accurate spring constant.
  • Take the reading of the angle of twist for vane shear test carefully by perpendicular eye position to the graduated ring.







Friday, October 2, 2020

Chemical Oxygen Demand

Information Civil

 Chemical Oxygen Demand

The chemical oxygen demand (COD) test measures the oxygen demand of the waste in account of the total amount of oxygen required for oxidation of the waste to carbon dioxide and water. The test is based on the fact that all organic compounds, with a few exceptions, can be oxidized by the action of strong oxidizing agents under acid conditions. 

Organic matter + Oxidizing agent = CO2 + H2O 

The reaction in above equation involves conversion of organic matter to carbon dioxide and water regardless of the biological assimilability of the substance. For example, glucose and lignin (biologically inert substance) are both oxidized completely by the chemical oxidant. In many cases  COD values are greater than Biochemical oxygen demand (BOD) values, when biologically resistant organic matter is present. Thus, there are a limitations of The chemical oxygen demand (COD) test is inability to differentiate between biodegradable and non-biodegradable organic matter. Another limitations that, inability to provide evidence of the rate at which the biologically active material would be stabilized under conditions that exist in nature. The time required for the evaluation of chemical oxygen demand (COD) test is very short, that is the major advantage of The chemical oxygen demand (COD) test. The  time required for The chemical oxygen demand (COD) test is about 3 hours rather than the 5-days required for the measurement of BOD. This is the reason for The chemical oxygen demand (COD)  is a substitute for the BOD test in many instances

Chemical oxygen demand title image

PRINCIPLE:

Potassium dichromate or potassium permanganate is usually used as the oxidizing agent in the determination of chemical oxygen demand (COD). In this class potassium permanganate would be used in the determination of chemical oxygen demand (COD). Potassium permanganate is selective in the reaction and attacks the carbonaceous and not the nitrogenous matter. In any method of measuring chemical oxygen demand (COD), an excess of oxidizing agent must be present to ensure that all organic matter is oxidized as completely as possible within the power of the reagent. This requires that a reasonable excess be present in all samples. It is necessary, therefore, to measure the excess in some manner so that the actual amount can be determined. For this purpose, a solution of a reducing agent (e.g., ammonium oxalate) is usually used.


APPARATUS:

  • Beaker (250 mL)
  • Dropper
  • Stirrer
  • Digestion vessels
  • COD Digester
  • Burette
  • pipette
  • A Round bottom reflux flask.

REAGENT:

  • Diluted sulfuric acid solution
  • Standard potassium permanganate solution
  • Standard Ammonium Oxalate solution.

PROCEDURE :-

Preparation of sample-

  1. Take about 10ml of distilled water in a round bottom reflux flask. Add 1ml of Mercury sulfate (MgSO4) and 5ml of Potassium Dichromate (K2Cr2O7) to the flask. The Potassium Dichromate used to oxidize all organic compound in the water sample
  2. Add about 15ml of diluted sulfuric acid to the reflux flask.
  3. Transfer the prepared solution to a Digestion vessel and place the Digestion vessel to a COD Digester for 2 hours. After 2 hours, move the Digestion vessel from COD Digester and rest it in a place and allow to cool for 30 minutes.

Titration of Blank solution-

  1. Transfer the solution to a conical flask and add about 2-4 drops of Ferroin indicator, The colour of the solution will changes to lite blue.
  2. Take 0.025M Ferrous Ammonium Sulfate to the burette and set the initial reading of burette to zero.
  3. Now start the titration until the colour of the solution taken in conical flask from blue to colourless. And take the final reading of burette as marked 'A' in the observation table.

Titration of the Water sample-

  1. Take 0.025M Ferrous Ammonium Sulfate to the burette and set the initial reading of burette to zero.
  2. The prepared solution taking in conical flask , and add 2-4 drops of Ferroin indicator, The colour of the solution will changes to lite blue. Then titrate the solution to the Ferrous Ammonium Sulfate taking in burette.
  3. Now start the titration until the colour of the solution taken in conical flask from blue to colourless. And take the final reading of burette as marked 'B' in the observation table.

OBSERVATION :- 

BOD table image



COD Formula image



PRECAUTION :- 

  • The complete Chemical oxygen demand test of a given water sample to be done in taken care.
  • During the test , the burette reading should be noted by observe as perpendicular position of eye to the burette.
  • Special care should be taken at the time of handle of COD Digester.



Tuesday, September 29, 2020

Direct Shear Test

Information Civil

Direct Shear Test

In the design and construction of bridges, foundation, retaining walls, skyscrapers, etc, the value of the angle of internal friction and cohesion of the soil involved are required for the design. The angle of internal friction and cohesion of the soil can be determined by the Direct shear test. The laboratory test of Direct shear test procedures for determining these values for cohesionless soils. 

Direct shear test title image

APPARATUS :-

  • Direct shear box apparatus
  • Loading frame (motor attached).
  • Dial gauge.
  • Proving ring.
  • Tamper.
  • Straight edge.
  • Balance to weigh upto 200 mg.
  • Aluminium container.
  • Spatula.

KNOWLEDGE OF EQUIPMENTS :-

The direct shear testing machine consists of shear box, soil container, loading unit, proving ring, dial gauge to measure shear deformation and volume changes. The direct share box can be splitted into two piece square shear box.  The shear load is  indicated by a proving ring which may be taken by the soil initiated in the shearing plane.

PROCEDURE :-

  1. Check and clean the shear box, shear mould. Measure the inner dimension and volume of the shear mould. 
  2. Assemble the soil container.
  3. Fill the soil in soil container in three layer by gently compacted.
  4. Weight the container and determined the volume. Distinguish the two weight and find out the density of the soil sample.
  5. Place the soil container to the shear box, and place the shear box to the Direct shear test instrument.
  6. Install the proving ring to determined the applied shear load. Set the dial gauge of the proving ring to zero.
  7. Install a couple of dial gauge for determine the normal load and the horizontal deflection. Set the both dial gauge to zero.
  8. Provide a normal load to the soil container by the arrangement of head weight. 
  9. To create a shear plain, remove the pin from the shear container of shear box.
  10. Start the motor, and take the appropriate reading of horizontal dial gauge corresponding to the proving ring.
  11. Add the normal stress of 0.5 kg/cm2 , and take corresponding readings, and noted down. 

OBSERVATION :-

Normal stress 0.5 kg/cm2    ; L.C=.......    P.R.C=.........

Direct shear test table image


Normal stress 1.0 kg/cm2   L.C=.......    P.R.C=........

Direct shear test table image


Normal stress 1.5 kg/cm2   L.C=.......    P.R.C=........

Direct shear test table image


Important in Direct shear test-

Plot a graph Normal stress vs. Shear stress, And a graph of Deflection vs. Shear stress.

PRECAUTIONS :-

  • Carefully clean the shear box and soil specimen in Direct shear test.
  • Carefully note down the weight and dimensions.
  • Take the readings of dial gauge by perpendicular view of eye and the dial gauge.



Wednesday, September 23, 2020

Biochemical oxygen demand

Information Civil

Biochemical Oxygen Demand

BOD title image

The biochemical oxygen demand  is a chemical procedure, which may be defined as the amount of dissolved oxygen needed by aerobic organisms in a water body to break the organic materials being present in the given water sample at specific temperature and a period of time. Biochemical oxygen demand (BOD) of a water sample can be determined as the amount of oxygen required for the biological decomposition of dissolved organic matter to occur under standard condition at a standardized time and temperature.  According to the BIS the recommended time specifically taken as 5 days and the temperature is 20°C. In the Biochemical oxygen demand (BOD) test during a specified incubation period it is measured the molecular oxygen utilized for the biochemical degradation of organic material (carbonaceous demand) and oxidize inorganic material such as sulfides and ferrous ion. The test also measures the amount of oxygen used to oxidize reduced forms of nitrogen (nitrogenous demand). The oxygen demand of typical waste is measured as the mg/litter. The saturated value of Dissolved oxygen (DO) for water may be  9.1 mg/L at 20°C. During the 5 days incubation period of the Biochemical oxygen demand (BOD) test the Dissolved oxygen (DO) should not drop to Zero, if so then the experiment may be concluded as invalid. 

PRINCIPLE: 

For the biochemical oxygen demand the sample may be filled in an airtight bottle and incubated at specific temperature for 5 days. The dissolved oxygen (DO) content of the sample is determined before and after five days of incubation at 20°C and the BOD is calculated from the difference between initial and final DO. The initial DO can be determined shortly after the dilution is made, molecular oxygen uptake occurring after this measurement is included in the BOD measurement.

The five-day BOD of a diluted sample is given by, 

BOD Formula image

DF formula image


In some Special cases, it may necessary to seed the dilute water with microorganisms to ensure that there maybe an adequate bacterial population to carry out the biodegradation. In such cases, two sets of BOD bottles must be prepared, one for just the seeded dilution water (called the "blank") and the other for the mixture of wastewater and dilution wader. The changes in DO in both are measured. The oxygen demand of wastewater (BODw) is then determined from the following relationship:

BODm formula image
BOD description image

APPARATUS:-

  • BOD bottle
  • Beaker (250 ml)
  • Measuring cylinder
  • Dropper
  • Stirrer

 REAGENTS:-

  • Manganous sulfate solution
  • Alkaline potassium iodide solution
  • 0.025N sodium thiosulfate
  • Starch solution (indicator)
  • Concentrated sulfuric acid.

PROCEDURE :-

In the procedure of biochemical oxygen demand need to test out a couple set of Dissolved oxygen (DO) test. Fill two BOD bottles with sample (or diluted sample); the bottles should be completely filled. Then immediately determine initial DO (DOi) in one bottle. Keep the other bottle in dark at 20°C and after particular days (usually 5-days) determine DO (DOf) in the sample (or diluted sample). Dissolved oxygen (DO) can be  determined by the following procedure:
  1. Add 1 mL of manganous sulfate solution to the BOD bottle by means of pipette, dipping in end of the pipette just below the surface of the water. 
  2. Add 1 mL of alkaline potassium iodide solution to the BOD bottle in a similar manner.
  3. Insert the stopper and mix by inverting the bottle several times. 
  4. Allow the "precipitates" to settle halfway and mix again.
  5. Again allow the "precipitates" to settle halfway. 
  6. Add 1 mL of concentrated sulfuric acid. Immediately insert the stopper and mix as before. 
  7. Allow the solution to stand at least 5 minutes. 
  8. Take out 100 mL of solution into an Erlenmeyer flask from the solution, and immediately add 0.025N sodium thiosulfate drop by drop from a burette until the yellow color almost disappears.
  9. Now Add about 1 mL of starch solution indicator to the flask and continue the titration process until the blue color just disappears. Note the amount of thiosulfate solution used (disregard any return of the blue color).

CALCULATION:-

Dissolved oxygen, DO (mg/L) = mL of 0.025N sodium thiosulfate added x Multiplying Factor (M.F.)

The five-day BOD of a diluted sample is given by,

BOD Formula image

 BODm formula image


RESULT:-

BOD table image





Saturday, September 19, 2020

Unconfined Compressive Test

Information Civil

 Unconfined Compressive Test

The bearing capacity of soil should find out, but always should not possible to conduct the test in same field. Sometimes  the Unconfined compressive test is conducted to laboratory by taking the undisturbed soil sample from the field. Other hand, the Unconfined compressive test is conducted to choose the best material for the embankment. The process are enlisted below to easily perform the unconfined compression test on undisturbed and remolded soil sample and the detailed  investigate experimentally the strength of a given soil sample.

Unconfined compressive test title image


EXPERIMENTAL PROCEDURE :-

The main concept of Unconfined compressive test is, a cylindrical form of a soil sample  is tested to failure in simple compression, without lateral support, at a constant rate of strain. The Unconfined compressive strength is defined as The compressive load per unit area required to fail the specimen. 

PRIMARY ASSUMPTIONS:-

Primarily We should find out the diameter and length of the specimen.

EQUIPMENTS :-

  • Loading frame of capacity of 2 t, with constant rate of movement. What is the least count of the dial 2.gauge attached to the proving ring.
  • Proving ring of 0.01 kg sensitivity for soft soils; 0.05 kg for stiff soils.

  • Frictionless end plates of 75 mm diameter (Perspex plate with silicon grease coating).

  • Soil trimmer.

  • Evaporating dish (Aluminum container).

  • Soil sample of 75 mm length.

  • Dial gauge (0.01 mm accuracy).

  • Balance of capacity 200 g and sensitivity to weigh 0.01 g.

  • Oven, thermostatically controlled with interior of non-corroding material to maintain the temperature at the desired level. What is the range of the temperature used for drying the soil.

  •  Sample extractor and split sampler.

  • Dial gauge (sensitivity 0.01mm).

  • Vernier calipers.


SAMPLE PREPARATION :-

A. Undisturbed specimen -

  1. Record the specific sample number, bore hole number and the depth excavated at which the sample was taken for further reference.
  2. The sampling tube should be cleaned and remove the protective cover (paraffin wax).
  3. The sampling tube extractor are placed to the sampling tube and push the plunger till a small length of sample moves out.
  4. Carefully Trim the projected sample using a wire saw.
  5. Again push the plunger of the extractor till a 75 mm long sample comes out.
  6. There should be taken care to cut out this sample carefully and hold it properly on the split sampler so that it does not fall.
  7. Take about 10 to 15 g of soil from the tube for water content determination.
  8. Note the container number and take the net weight of the sample and the container.
  9. Measure the diameter at the top, middle, and the bottom of the sample and find the average and record the same.
  10. Measure the length of the sample and record.
  11. Find the weight of the sample and record.

B. Moulded sample -

  • For the determination of Unconfined compressive test , calculate the weight of the dry soil (Ws) for the desired water content and the dry density, required for preparing a specimen of 3.8 cm diameter and 7.5 cm long.
  • Now the required quantity of water (Ww) is added to this soil, and mix it properly,
                          Ww =( WSxW)/100 gm

  • The wet soil is placed in a tight thick polythene bag in a humidity chamber.
  • After 24 hours the soil take out from the humidity chamber and the soil should be placed in a constant volume mould, having an internal height of 7.5 cm and internal diameter of 3.8 cm.
  • The lubricated moulded should be placed with plungers in position in the load frame.
  • The compressive load is applied till the specimen is compacted to a height of 7.5 cm.
  • Then the specimen should be ejected from the constant volume mould.
  • The correct height, weight and diameter of the specimen should be recorded in a proforma for calculation purpose.

TEST PROCEDURE :-

  1. Take two frictionless bearing plates of 75 mm diameter.
  2. Place the specimen on the base plate of the load frame (sandwiched between the end plates).
  3. Place a hardened steel ball on the bearing plate.
  4. Adjust the center line of the specimen such that the proving ring and the steel ball are in the same line.
  5. Fix a dial gauge to measure the vertical compression of the specimen.
  6. Adjust the gear position on the load frame to give suitable vertical displacement.
  7. Start applying the load and record the readings of the proving ring dial and compression dial for every h) 5 mm compression.
  8. Continue loading till failure is complete.
  9. Draw the sketch of the failure pattern in the specimen.

OBSERVATION :-

Code followed:    IS : 2720 (part 10) : 1991

Type UD/R : soil description

Specific gravity (GS)=  2.71                                                Bulk density =

Water content = W                                                       Degree of saturation =    %

Diameter (Do) of the sample=  3.8cm                     Area of cross-section =    cm2

Initial length (Lo) of the sample = 76 mm  

CALCULATION :- 

Unconfined compressive test table image

Unconfined compression strength of the soil = qu =

Shear strength of the soil = qu/2 =

Sensitivity = (qu for undisturbed sample)/ (qu for remoulded sample).







Tuesday, September 15, 2020

Dissolved Oxygen

Information Civil

Dissolved Oxygen in a water sample

The amount of oxygen present in water is called as Dissolved Oxygen (D.O). The Principle involved in the determination of Dissolved Oxygen (D.O) as about the oxidation of KI to I2 with dissolved oxygen present in water sample, after addition of MnSO4, KOH and KI. The basic manganic oxide MnO(OH)2 formed acts as an oxygen carrier to enable the dissolved oxygen in the molecular form to take part in the reaction. The dissolved oxygen (D.O) in water oxidized KI to I2 and liberated I2 is titrated with (N/10) Na2S2O3 solution.

Dissolved oxygen title image


PRINCIPLE :-

WINKLER METHOD :

Oxygen present in water oxidises Mn+2 to Mn+4 in presence of alkali iodide-azide solution and these Mn+4 in presence liberates I2 from KI in acidic medium. The amount of I2 liberated is equivalent to dissolved oxygen O2 present in water and the liberated I2 is estimated by titration with Na2S2O3 solution using starch as indicator.

MnSO4+2KOH ®Mn(OH)2+H2SO4

2Mn(OH)2 +H2SO4®2MnO(OH)2[basic manganic oxide]

MnO(OH)2+H2SO4® MnSO4+2H20+[O]

2KI +H2SO4+[O]®K2SO4+H20+I2

I2+2Na2SO3®Na2S4O6+2NaI

Starch+I2®Coloured complex

CHEMICALS :-

  • Water sample
  • MnSO4 solution
  • Alkali-iodide-azide solution(NaOH,KI,NaN3)
  • Conc.H2SO4 (v)(N/10)Na2SO3 solution
  • Starch indicator


APPARATUS :-

  • Conical flask
  • Burette
  • Measuring cylinder
  • Beaker
  • Volumetric flask
  • Funnel
  • BOD bottle
  • Glass rod etc.


PROCEDURE :-

About 200 m.l of water sample is taken in a BOD bottle(~300 m.l capacity).To it 1m.l of alkali-azide-iodide solution is added and stoppered the bottle immediately and shaken well. Appearance the brown ppt. of manganic oxide indicates the presence of Dissolved Oxygen. The ppt was allowed to settle down. Then add 1 m.l conc.H2SO4 to dissolve the ppt.Now, total solution is taken into a conical  flask and liberated I2 is titrated with (N/10) Na2S2O3 solution, until the colour of the solution turns pale yellow.2 m.l of starch solution (indicator) is added and the titration is continued. The end point is colourless.

OBSERVATION :-

Table:1,  Estimation of Dissolved Oxygen in H2O

Dissolved oxygen table image


CALCULATION :-

The amount of Dissolved Oxygen in the supplied water sample  = V X Conc. of Na2S2O3 X 8 X 1000/Total volume of sample

 Where, V = Volume of Na2S2O3 solution Conc. Of Na2S2O= (N/10)=0.1(N)

                                                            8 is the equivalent wt .of O2

Total volume of sample = 203 m.l

PRECAUTION:-

  1.  After the addition of reagents in water sample taken in BOD bottle there should not be any air bubble present because it will give high Dissolved Oxygen value.
  2. As far as possible, the sample should not be allowed to come in contact with air.




Friday, September 11, 2020

Softening point of bitumen

Information Civil

 Softening point of Bitumen

The Softening Point of bitumen or tar is the temperature at which the substance attains particular degree of softening. As per IS: 334-1982, it is the temperature in ºC at which a standard ball passes through a sample of bitumen in a mould and The ball falls through a specific height of 2.5 cm at a specified condition, when heated under water or glycerine. The binder which is used in construction of road,  must have sufficient fluidity at the time of road construction. The main reason to determine the softening point of bitumen, the maximum permissible  temperature can be heated to a bituminous binder for various road use applications.

Softening point title image


APPARATUS :

  • Ring and Ball apparatus

  • Water bath with stirrer

  • Thermometer

  • Glycerin

  • Steel balls each of 9.5mm and weight of 2.5 ± 0.08gm.

PROCEDURE:

  1. Firstly heat the bitumen sample to a temperature between 75 ̊ – 100 ̊ C  and stir by a glass rod until, the bitumen changes its state to liquid and free from air bubbles and water. If necessary it can be filtered through IS sieve 30 mm. Previously heated Rings are placed to a temperature approximating to that of the molten material On a metal plate. The metal plate used   in softening point of bitumen should be coated with a mixture of equal parts of glycerin and dextrin. Leave it in open atmosphere 30 minutes for cooling, removing the excess with a warmed, sharp knife to level the material in the ring.
  2. Assemble the Softening point apparatus with the rings, thermometer and ball guides in prescribed position.
  3. Filling the water bath with the distilled water to a height of 50mm above the upper surface of the ring to a temperature of 5 ̊ C.
  4. Now gradually heated to the bath and stir the liquid so that the temperature rises at a uniform rate of 5± 0.5 ̊ C per minute for the test of softening point of bitumen.
  5. The temperature is the softening point of bitumen when any of the steel ball with bituminous coating touches the bottom plate, Carefully note down the temperature.

OBSERVATION - 

Softening point table image


RESULT :

The Softening value of given bitumen is ________________ .

PRECAUTIONS :

  1. Should be careful the entire softening point experiment, and especially at the time of the heating of bitumen.
  2. Temperature should well controlled to the water bath.
  3. Should be taken care at the time of coating the metal plate.
  4. There shall be no smoking or the presence of other ignition sources in close proximity of test set-up.
  5. Distilled water should be used as the heating medium.
  6. During the conduct of test the apparatus should not be subject to vibration.
  7. The bulb of the thermometer should be at the same level as the rings.





Tuesday, September 8, 2020

CHLORIDE ION IN WATER

Information Civil

 Chloride-ion in Water

Chloride ion icon image

Chloride ion can be determined by titration of water sample against a standard solution of AgNO3 using Potassium Chromate as indicator, in a neutral or slight alkaline medium. When AgNO3 solution is added to the water sample in presence of K2CrO4,the chlorides present in it are precipitated as AgCl. All the Chlorides are precipitated out even a drop of AgNO3 added in excess gives a red precipitate of silver chromate, this indicates the end point.

REACTION:

 AgNO3+NaCl®AgCl¯ +NaNO3

                        (white ppt.)

AgNO3+ K2CrO4® Ag2CrO4 ¯ +2KNO3

                               (Red ppt)

The PH of the solution should be in between 7-8, because at higher PH, Ag+ ion is precipitated as AgOH.

            Ag++OH-®AgOH

If the PH is lower than 7-8 then the chromate ion is converted to dichromate ion.

   2CrO42-+2H+=Cr2O72-+H2O

       The required PH range can be achieved easily by adding a pinch of pure CaCO3.Excess CaCO3 being insoluble , does not interfere.

      2H++CaCO3® Ca2++CO2+H2O

APPARATUS:

  • Conical flask
  • Burette
  • Measuring cylinder
  • Beaker
  • Dropper
  • Volumetric flask

PROCEDURE:

  • Blank Correction:

i)Take 25 ml distilled water in a beaker and add 3-4 drops of K2CrO4 indicator.

ii)Titrate against (N/50) AgNO3 solution till the brick red colour appears in the solution.

iii)Repeat the Titration.

  • Sample water titration:

i)Take 25 ml of water sample in a beaker and add a drop of methyl orange. If red or pink colour appears, add a pinch of CaCO3, red or pink colour disappear.

ii)Add 2-3 drops of K2CrO4 indicator and titrate against (N/50) AgNO3 solution until the red colour appear in the solution.

iii)Repeat.


OBSERVATION:

  • Table 1: Blank Correction-
Chloride table 1 image


  • Table 2: Sample water-
Chloride table 2 image

CALCULATION :-

We know,

                                                V1S1=V2S2

                                                S2=V1S1/V2        


                                                                                                 V1=Volume of AgNO3 sol.

 S1=Strength of AgNO3 sol. =(N/50)

V2=Volume of water

S2=Strength of water


V1= |Vol. of AgNO3 sol. Of sample water-Vol. of AgNO3 sol. Of distilled water|

Strength of Chloride ion = S2X 35.5 g/l

                                           =S2 X 35.5 X 1000 mg/l

\The Chloride ion concentration in the given sample is ______mg/l.


PRECAUTION:

i)The glass apparatus should be washed with distilled water before Chloride ion test. 

ii)Volume of the indicator should be same in all titration.

iii)The end point should be noted when a tinge of brownish red colour persists.






About

  • Somen BhattacharjeeCivil Engineer