Estimation of Copper present in the given solution by Colorimetric Method by Dr. T Lakshmi Viveka

Added: 2026-05-20

[00:00:08]Hi everyone, I am Dr. Lakshmi, assistant professor department of chemistry in VNR VJ. The subject it is engineering chemistry laboratory. Today we have to learn about instrumental technique that is called as a calimetric method. What is the calometric method? What is the importance of this calrometric? Just you have to observe some images some tomato catchup some fabrics with the color and dyes with the different colors and blood cells. So what is the common point in all these? So that is a color colored substances. So here these color substances consists of some amount of metals and how much intensity of metals are present in that and how we can determine all these things by using this calorimetric method. So coming to the main objectives of this uh uh experiment it is uh we have to measure the light absorption of solution at a specific wavelength determination of concentration of substances using B Lambert's law. It verifies the B Lambert's law and it can analyze the colored compounds in chemistry, biology and medical laboratories.

[00:01:19]Can compare the intensity of color between standard and unknown solutions.

[00:01:26]Coming to the applications of colorometric technique, it is used in very so many industries mainly for the bioclinical estimation. We have to use this calorimeter for bioclinical estimation. Mainly it is used for the blood glucose levels for diabetic testing and then uh uh protein estimation and how much amount of protein concentration in biochemical and clinical samples and how much amount of hemoglobin is present in blood samples.

[00:01:55]Mainly it is used in hospitals and pathological uh labs. It is used to determine the impurities and how much amount of impurities and pollutants. Uh some amount of metal ions which is present in the water it can determined for water quality check. Then uh pharmaceutical analysis mainly it is used in pharmaceutical industries for drug and chemical analysis.

[00:02:20]Now coming to the calorometry technique uh here we have to mainly focus on what is the light which is passed into the uh solution. What is the light and what is the source of light and this source of light in electromagnetic spectrum and what is the range and this range it is in between 400 to 700 nanometers and what is the instrument what are the components of uh these instruments we have to learn today.

[00:02:52]Coming to the schematic diagram of this calm technique and how it will be works.

[00:02:56]What is the working principle of this calm technique? Uh we should know about this one. So here the source of light what is the source of light we are using here? This is called as a monochromatic light. So the monochromatic light wavelength it is in between 400 nanome to 700 nanometers. Whenever it light passes through a prism. So the monochromatic light it diverges it in the form of VGR. So this VGR has a different colors. Each color has its own wavelength. Here whatever the solution we are taking into the Kuvate that based upon the solution color we can choose the wavelength. That wavelength we can set up by using the filter disck. And here based upon the how much amount of instant light is passed through the solution and how much amount of light is emitted that is called as a transmitted light. Based upon that we can take the absorbance values in the display. So that display values it is in terms of optical densities. Optical density or absorbance values we can get on the display. So now coming to this main part what are the components which are present in the uh colorimeter. What are the main components? Source of light.

[00:04:08]The source of light is a white light.

[00:04:09]The range of white light is visible light. It is in between 400 to 700 nanometers. And the filter it is a monochromat. It selects a specific wavelength. And the kuet we are using that kuet which is placed in a kuet holder and this kuet it is used to hold the sample that is either test solution or prepared solution. Then coming to the photo detector. This detector it can detects the transmitted light. This detector it detects the transmitted. How much amount of light is transmitted through this solution? This can be detected by using the photo detector.

[00:04:40]And coming to the finally it is called as a display. This display shows the absorbance values based upon the concentration. So this is about the uh basic instrumentation of spectr photometer. So coming to this uh experiment the main aim of this experiment is we have to estimate amount of metal ions present in metallic solution. So that metallic solution either we have to take copper sulfate or something ferrulfate whatever it may be.

[00:05:08]So whatever the solution we are taking that solution should be the complex formed it should be colored complex. So based upon the color we can set the wavelength. Here metal ions the copper ions we have to uh estimate this copper ions we have to estimate by using this uh given solution that given solution the test solution it is called as a copper sulfate pentahhydrated solution. So here for doing this experiment first we have to prepare a solution in different uh categories. So first for calibration we have to use a blank solution that what is a blank solution? Why we have to use that blank solution we have to know. Then what is the standard solution? How many standard solutions we have to prepare? All this we have to know. And what is the test solution? Based upon this uh concentration, how we can determine the uh estimated uh that is metal ions which is present in the metallic solution. We can determine using C colorometer technique. So here uh already I told you that is called as a copper sulfate solution. This copper sulfate solution we are taking that is called as a stock solution. What is a stock solution? This stock solution suppose I need to prepare one liter of solution. For this we take uh 8 g of copper sulfate. It dissolves in one liter of distilled water. Here what is the concentration here? 1 liter it consists of 8 g. So 1 ml it consists of 8 mg concentration. So whatever the solution we prepared and that solution we have to uh use that is called as a stock solution. that stock solution uh first we have to place in a beaker. So we have to charge into beaker and uh we have to add uh that solution that is called as a ammonium hydroxide solution.

[00:06:57]The main ligon is ammonia. This ammonium hydroxide how we can prepare ammonia and water in equimar ratio we can get ammonium hydroxide. So this ammonium hydroxide we have to add to this copper sulfate solution. Then it forms as a complex that complex it is called as a tetraamino complex. So this complex how it will mention. So here this is a central metal that is called as copper and it donates the lians to this central metal.

[00:07:29]So these lians are neutral NH3 NH3 and it forms a outer sphere that is SO4 minus2. So the oxygen state of copper it is plus2. So we can mention it is as how many lians are presented attached to the central metal four. So it is called as a tetra amino copper to sulfate. So this complex it is formed in the form of blue colors. Initially it is a pale color and finally after formation of uh complex it forms as a dark blue color.

[00:08:04]So let us know how to prepare the standard solutions for for that uh what are the apparatus and reagents are required for this experiment you should know. So mainly stock solution we are using that stock solution is called as a copper sulfate pentahhydrated solution and then complexing reagent we are using that is called as ammonium hydroxide solution and distilled water we are used for making the standard solutions here we need standard flask or volutric flask 100 ml of volutric flask eight flasks are required then kuet it is used for determination of absorbance of that particular solutions then we are using the major instrument that is called as a calorie meter Then bureates. Bureate it is used to measure the solution which is filled in each standard flask. Then pipet it is used for making to uh making the solution up to 100 ml up to the mark. We have used the pipet. So these are the apparatus and the reagents. And this is the setup for this uh technique.

[00:09:03]Now coming to the experimental procedure. Just observe here uh here these are the different labeled uh standard flask. Each flask is labeled with a different volume. So it starts from 5 to and ends with the 35 ml. 5 10 15 20 25 ml 30 35 ml uh labeled volumetric flask we have to taken. Then what you have to do first we have to take the copper sulfate solution in uh that is 250 ml beaker and we have to fill the bureate with the copper sulfate solution in bureate. So after filling the bureate just you have before filling uh the knob it is closed.

[00:09:45]After filling just you have to check the nozzle portion is there any air gap is present in the uh bureate just you have to remove the air gap and fastly run on the solution and make up to zero level.

[00:09:57]So then uh uh this bate you have to fix to the bate stand. Then just observe here. First what you have to do? We have to fill the copper sulfate as per that volume in each standard flask that is from 5 to 35 ml.

[00:10:17]Then to that what we have to add we have to add a complexing reagent that is called as a ammonium hydroxide. In each standard flask we have to add 5 ml ammonium hydroxide. [snorts] Just you have to observe here in each standard flask you have to add 5 ml of ammonium hydroxide. You have to measure by using the measuring cylinder and transferred into copper sulfate solution. Then it turns to dark blue color. Then shake the solution then make up to 100 ml by using distilled water. So for that we have to add distilled water up to the neck portion. So up to the neck portion we have to add and the remaining portion use dropper up to the mark. Here this is a colored solution. So color solution the miniscus part upper miniscus we have to consider. So in this way we have to prepare the solutions for different concentrations that is from 5 to 35 mm.

[00:11:16]5 ml to 35 ml and also we will give you an unknown solution that unknown solution concentration you don't know you have to find out by plotting a graph between volume of copper sulfate on x-axis and the optical density values on y axis for that to the unknown solution uh concentration we have to find out how much amount of copper is present in that unknown solution. So now coming to the determination of optical density we have to use an instrument that instrument is called as a calorimeter technique. So these calorimeter it consists of different components just you have to observe the instrument and it shows the display and 61 it shows that is called as a wavelength. So here uh here this is the percentage of transmittance the percentage of transmittance and the same button we have to use as a auto zero this is used for calibration purpose.

[00:12:20]Why we have to use this uh why we have to do the calibration? Any instrument before doing the experimentation we have to calibrate for uh to get accurate results to accuracy we have to calibrate the instrument. For calibration we are using a solution that is called as a blank solution. What is a blank solution? Why we are using blank solution? So blank solution means here what we have to do we have to determine the intensity of the color and based upon the wavelength we can determine the absorbance. So that is that solution it has some metal ions. Here we are taking a solution it has no color and no ions present in the solution. No color and no ions. So no color and no ions means it has a blank solution. So this blank solution first you have to fill in kuet.

[00:13:11]So that kuvet we have to place in the kuet holder and up to the 3/4 you have to fill in the kuet. Then uh we have to follow the operating instructions here. First switch on the instrument and then we have to select the appropriate mode of uh wavelength that is 61. We can choose the wavelength either 58 or 61 or 65 based upon the solution color formed complexes. Based upon that we can choose the color either we can increase or we can decrease the color. And here C1 and C2 are the mode of calibration. C1 C2 are the mode of calibration. When we press the C1 button and uh uh we can that mean the light will blink at that particular we need optical density values optical density values. So here first you switch on the instrument and select the wavelength then place the kuate with the blank solution and place it is in the ket holder then press auto zero button uh that is absorbance zero then automatically it comes to zero then uh what you have to do we have we prepared already different concentrated solutions now replace the blank solution with the different solutions uh we can find out the concentration for each solution so you mainly Focus on what is the calibration and why we have to do the calibration. What is the purpose of blank solution and what is the blank solution we are using? That blank solution is called as a distilled water.

[00:14:38]Why we are using distilled water?

[00:14:40]Because it has no color and no ions, no color and no ions in the distilled water. That's why we have to choose distilled water as a blank solution. So the absorbance value for this distilled water is zero. Then it is calibrated.

[00:14:55]And which filter number we are using that is 60 in some instruments. In some other instruments it shows 61. That means it is multiplied with 10 nanome that is either 600 nanome or 16 nanometers. Right? So the wavelength we can choose. Why we have to choose that particular wavelength? Because the colored complex it is a blue color solution. So the complimentary color wavelength we have to set that is in between 580 to 620 nanometers or sometimes it is a 590 to 610 nanome. So uh this range the blue color complex wavelength it is in between five uh 80 to 620 nanometers range it is present. That's why you have to choose a 61 or 60 filter number. So here uh you mainly focus on what is the filter number, what is the importance of filter number, all these things. So filter number uh means uh already you know that colorimeter technique uh it is an instrument to measure the concentration of the color substances in solution by measuring the amount of light absorbed. It uses filters to select specific wavelength of light. So whatever the filter disc we are using that filter disc it is in the circular uh rotating plates. These circular rotating plates containing different colored optical filters. So here when just you have to observe here the blue color then or green then orange or red color. So these are the complimentary colors of the particular solution. So we can choose that filter based upon the color solutions. So what is what is the uh role of these filter discs? What filter disck helps in different ways that is we can choose the wavelength selective wavelength then uh improving the accuracy uh and then absorbance of a measurement then uh matching the complimentary colors of the solution. Just observe here when look at this picture a light which is passes through the prism that light is a monochromatic light. This is the monochromatic light.

[00:17:03]Whenever it is enters to the prism, we can get different colors. Each color has its own wavelength. So already we discussed in the previous slides. So this is uh the light which is passed through the uh prism we can get different wavelength that light which is passed to the solution. So based upon that uh we can get the absorbance values. See here whatever the light which is enters into this prism or solution that light is the monochromatic light. It is under the visible light.

[00:17:34]This visible light it is present in the electromagnetic spectrum. It is a small portion in the electromagnetic spectrum that is in the range of 400 to 700 nano m.

[00:17:46]And here uh some uh instruments it shows a filter disk and filter numbers. Some instrument it is in the form of percentage of transmittance that is C1 C2 modes. Then uh um in the form of wavelength that is 61 into 10 that is 16 nanometers. This is the nanometers set we have to set. So I already told you why we have to choose that particular wavelength 61 filter number. Why you have to choose? Because the whatever the solution we are using that solution is a blue color. So that blue color complimentary color uh filter disc consists of either orange or red it is in the range of this 600 nanometers.

[00:18:30]That's why we have to choose that particular wavelength.

[00:18:34]Now here when monochromatic light passes through a colored solution some specific wavelength of light are absorbed which is related to the color intensity. The amount of light absorbed or it is transmitted by a color solution. It is in the accordance with the two laws. So they are called as a beer law and lambert's law. So combine combiningly these two are called as a beer lambert's law. So this be lambert's law can be explained by this uh principle. Here whatever the light which is passes through a solution. Here this solution it is the color solution. Um that complex we have to place in a kuet. Here suppose 100 percentage of light which is incident that is I not is called as a incident light. So 100%age of light is incident through the solution. Some amount of light is absorbed and remaining light is emitted. 100 minus x is called as a emitted light. So it t is called as a emitted light or transmitted light. So here how we can find out the percentage of transmittance. The percentage of transmittance it is equal to emitted light divided by incident light I not into 100. Okay. Now so uh percentage of transmittance is I divided by not into 100. So what is the relation between the absorbance and transmittance? So these both are inversely proportional. Absorbance is inversely proportional to transmittance.

[00:20:01]Suppose we take a blank solution. So the blank solution has no color and no ions.

[00:20:06]So absorbance is zero. So transparent light is 100% of light is passed through the blank solution. Then what happens?

[00:20:12]Same amount of light is emitted because it has no no concentration that's why it is emitted. So 100% of transmittance absorbance zero transmitted is a 100%.

[00:20:24]So it is inversely proportional. When the absorbance increases transmitt decreases. Okay. So the relation between the absorbance and transmittance just you have to remember. Now coming to the beer lambert's law. What is a beard's law and what is a lambert's law? So absorbance uh so here we are using concentrations different concentrations that is 5 to 35 ml. When the uh color solution increases that means the concentration of the solution increases intensity of color also increases then we can get the absorbance values differently. So absorbance it is directly proportional to the concentration of the solution and path length. Path length means it is the thickness of the absorbing medium. So simply we can say that A is equal to epsilon C into L. So epsilon is called as a proportionality constant. This is equation one and in terms of transmittance we can mention it is as absorbance is a negative logarithm of transmittance. So negative logarithm of transessance means here negative log I T means already you know that it divided by I. So simply you can mention as equation two. So combining these two epsilon CL L is equal to negative log of T. So finally the B lamb's law expression A is equal to epsilon C L equal to negative log of I by it divided by IN. So this is a B lambert's law expression here. Which one is a beer's law? So B's law is a absorbance is directly proportional to the concentration is a beer law and absorbance is directly proportional to the path length or thickness of the absorbing medium. That absorbing medium means either it is a quartz or glass or whatever the material we are used for making this cuet. So the thickness of the absorbing medium that is called as a path length. This is a Lambert's law. So by combining these two we can say that.

[00:22:21]So yeah decreasing intensity of the light is directly proportional to the intensity the concentration of the solution and then path length just you have to observe already we prepared different solutions when you are take the absorbance values so just you have to starts from 5 ml it the value for 5 ml is.11 it is missed here and coming to the 10 ml the value is 22 observed here in the instrument point and 15 ml it is a.33 for 20 ml it is 44 25 ml 55 so it will be deviation is there for 30 ml then 35 ml so finally we take the unknown solution for unknown solution also we have to prepare in same way like that we take the uh we will give you some solution we have to add complexing reagent 5 ml then make up to 100 ml by using distilled water that we have to place in a kuet holder uh kuet that is placed weight holder you can get the absorbance values. So now plot a graph between volume of copper sulfate on x-axis the optical density values or absorbance values on y-axis. So here we can get a straight line all the values you have to plot it on the in this graph then you can get a straight line that passes through origin. Here optical density suppose is a 29. So this 29 uh it uh curves the straight line and it touches the x-axis. So that indicates that uh this is the in from these values we can get 13 ml is the unknown concentrated volume. So that 13 ml. So already uh we know that the stock solution concentration is 8 mg. So that 8 mg we have to substitute here that is amount of copper which is present in the unknown solution that is the W1. W1 is a 13 into 8 mg we can get 4 mg. Then amount of what is the aim of our experiment? We can estimate the metal ions present in the metallic solution.

[00:24:26]So W2 we have to find out that is how we can find out W1 into molecular weight of copper that is 63.5 divided by molecular weight of copper sulfate pentahhydrate 249.7.

[00:24:39]So we can get finally these uh values 26.44 mg. So this is the final result of our experiment the amount of copper present in the given sample solution. So that is a 26.44 mg. So um here just uh take the error values error how we can find out based upon the given values. So given values uh we can find out the error percentage of error correct. So this is about the instrumental technique color.

[00:25:11]So uh so now finally go for the recap what you understand from this uh uh experiment. What is the purpose of using calorimeter and what is the complexing reagent we are using? What is the name of the complex formed? What is the blank solution? What is why we are using this blank solution? Why don't we use uh other solutions? What is the calibration curve? And then uh source of light which one we are using and what is the filter we are using and what is filter number what are the different applications of colorometer all these things. Thank you.

[00:25:42]We will meet in the other video.

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