Calcium-EDTA titration
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- เผยแพร่เมื่อ 22 ม.ค. 2009
- This video demonstrates the titration of calcium with an EDTA titrant. The indicator used is another chelating agent, Eriochrome Black T. The color transition can be very difficult to see due to the very gradual change in color of the indicator over the course of the titration.
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Thanks for the strategies you have shared here.
Aghnia Maraya The water is added to help the mixing and to provide a bit more volume to better see the color change. The dilution doesn't change the results, as it is simply a reaction between the number of moles of Ca and EDTA once the titration begins.
Thank you for your kind reply. I never did that in any experiment we've done thinking it can affect the results.
Thanks mate...for the demonstration!
Yes, in all titrations you typically make a somewhat dilute solution of your titrant. You will then use that titrant to titrate a pure standard so that you can know the concentration of the titrant accurately. Then you can use that titrant to titrate an unknown and accurately determine the amount of analyte (in this case calcium) present in the solution.
The water is added to increase the volume of the solution to ensure that it mixing in the flask is easy and done completely. Often with only a 10 mL aliquot in a 125 mL flask, there volume of analyte is only enough to just coat the base of the flask. Adding the extra water makes it easier to mix and in some ways, see the color of the solution.
Hey man, great vids just one quick question.
Im wantint to titrate samples of milk in determining calcium quantities, what would be my best process and what would me reactant be in which I mix the calcium with ? If you could reply ASAP would be very grateful :)
The amount of buffer is likely to need to be varied depending on the amount of acid involved in the preparation of the calcium sample. However, in this instance a 2 M ammonia buffer at pH 10.
Great video!!
I'm titrating iron(III) against EDTA with a salicylic acid indicator for a high school experiment. Do you have any idea what concentration indicator to use, I don't want the acidity to affect the titration! Thanks in advance if you get back to me.
Ok thanks :) for lead, since it's colorless, shall I use erichrome black T to color it first? Should I do direct or back titration? If you do come across any link could you please share it here?(for lead) thank you!!
Very cool!
how much buffer did you use and is there a reconmended amount
@crharrison
ya we used Buffer to stablize the pH it was the EBT for the total and then Muroxide selective for the Ca..
We used something called HSNNA as an indicator when measuring the mass of the calsium. The we added some hydrogen peroxcide and removed the blue colour. And after that we used Erio T as an indicator when measuring the mass of magnesium. PH was above 10 the whole time (except when removing the sedimented calsium with hydrogen chloride)
@rockindxb1 This titration method could be used for the measurement of water hardness. Hard water is typically due to the presence of calcium and magnesium ions (and some other trace metal ions). All these metal ions can be complexed by EDTA; in 1:1 complexes. So the total number of moles of metal ions can be determined. This won't give you the typical water hardness units (mg/mL), or specifics on which metal ions are present, unless you assume the only one type of metal ion is present.
Hi, I saw in this experiment that you are rinsing the sides of the flask with water. Does that in any sense, affect the titration?
THANK YOU VERY MUCH :)
@leytonhewit1 Sorry for the delay in getting back to you. This analysis might work for clear juices (e.g. apple) but there are a few things you will need to consider in the analysis:
- presence of other salt cations interacting with EDTA (e.g. Na, Fe...)
- citric acid and some proteins can interfere with the complexation of cations with EDTA
-the pH needs to be adjusted prior to the analysis
It's worth a try, though you may want to use a standard addition method for accuracy of the analysis.
Provided that you buffer the solutions (or adjust the pH) sufficiently there shouldn't be a problem. The optimal pH for the EDTA titration is around 9; it appears that this will change the color of your indicator but that shouldn't be a problem. One think you may wish to verify are the formation constants for the two complexes as this titration will only work if the EDTA-Fe(III) formation constant is greater than that of salicylic acid-Fe(III) complex. I presume it is but I haven't checked.
THANK YOU VVV.MUCH AGAIN :):)
Can it be used for the analysis of the hardness of water? If yes how can we determine it?
I am just confused 'cos this other titration got got us to use an NaOH 1g powder of i think 1molar that we had to mix with 100m to make a dilute solution out off. Do you have to make a dilute solution of EDTA as well?
Well-done vid mr. Harrison !
The diff between this & other titrations is you need to go slow, else one misses the eq point because of the slow reaction.
An other indicator that works for Ca is Calconcarboxylic acid solution.
( Eriochrome T also reacts to Mg.)
For rather low Calcium conc. one can ( after adding KOH to pH 12~13 ) add a known amount of CaCl2
until blue, then titrate with the EDTA; when doing the math subtract the amount of added CaCl2.
How much percent KoH solution should be used to increase ph 12 ~13
@fabulousmango slightly larger amounts of magnesium in the titrant shouldn't impact the titration; the complexation factor for EDTA:Calcium is about 1000x greater than EDTA:Magnesium. So unless you have grossly too much magnesium you shouldn't impact the endpoint. There may be some impact on the color, as that is the result of the indicator complexing with free metal; having more magnesium to complex with might alter how clear the color change is.
does the addition of distilled water affect the results of the experiment? I only ask 'cuz we're adding something to the solution. Does that cause any aberrations whatsoever?
What would happen if too much magnesium chloride hexahydrate was added? Would the endpoint be pushed back?
@qrais Your ability to get very accurate results may decrease. This is because every drop of titrant will contain larger amounts of EDTA the last drop required to make the colour change may contain far more EDTA than necessary. But otherwise there is no detriment to using higher concentrations of EDTA.
Im testing for harness of bottled water samples. I add 1ml of ammonia to 10ml of the water then heat the water untill condensation forms on the rim. Then i add the calmagite indicator but when i titrate with the edta the most it ever takes is 3-4 ml to turn dark blue.
I've just did this todaaaaaaaaay..!!!
it was a mixture of Ca\Mg sample using the total end point and subtract the Ca from it to get the Mg ofcourse we made the Mg ppt and the second time..but ya..it was coool and i do see these colors..
Can I know, does this work for lead?
Yeh I ended up doing multiple titrations until it worked out. What I found out was when I tried titrating just milk from the bottle with EDTA and eriochrome the milk chelated the ions immediately before the EDTA had a chance. Thus there was no actual starting point just get an end point immediately. If you could shed some of your knowledge on this would be helpful because am a little confused with what the whole purpose of chelating is etc etc
@thetrueturnip That's not too surprising, given how low the concentration of calcium is likely to be in bottled water. If you are looking to improve your accuracy you might want to try titrating larger samples of bottled water (e.g. 100 mL) or diluting your EDTA (10 fold dilution). This way you may be able to get some better differentiation between sampels; as the concern with titrating a simple with too little solution is the chance of overshooting the endpoint is much higher.
@idiotkrati I'm not certain, it would really depend on how low the pH of the EDTA solution was (and that depends on what form of EDTA you are using). One way to overcome that would be to use a higher concentration of buffer to mitigate the pH changes should they be occurring.
@CelestialPlatypus Yes. Otherwise the students become overstimulated and cannot focus on their work properly ;-)
The reality is that's just what happens to my voice through multiple takes while trying to narrate a video at a steady pace, clearly and without stumbling over my words. Perhaps I'll try to liven my voice up a bit more in future recordings, but from what I can tell, I'm not nearly as monotone in my lectures.
@22fause21 No, the water, so long as it is free of any metals, will not have any impact on the titration. Pure water can be added to most aqueous titrations with no consequences as titrations are not concentration dependent.
I'm doing this experiment tomorrow
when i use 50 ml tap water + 2 ml NaOH + Pathon & Reeder's indicator. its give blue in colour . its not giving red wine colour and when i use ground water it also give like that. so please help me and alternately i use Eriochrome Black T indi. with 0.02 M EDTA sol. plz plz help me
Sorry for the delay in the response, things have been busy. Hopefully you've been able to find the answers to your questions, but if you haven't I suggest that you do a Google search for "EDTA calcium titration procedures" (without the quotes). You'll find that there are plenty of university sites that have posted the procedure to this lab online. Good luck.
The addition of water (provided it is distilled/deionized) will not impact the titration. If you are adding tap water (which will contain calcium and other metal ions) you will have problems with the results.
Pure water can be added to just about any aqueous titration, the dilution of the reagents doesn't impact the reaction as the reaction is based on the number of moles not the concentrations.
thanks
Insaaaaaaneeeee!!!! :D
Hey my titration doesnt show end point .... Not changing the colour .....
please help me
Hi I'd like to ask a few questions.
1. Would the experiment work if I used milk as the calcium sample?
2. How much buffer solution should you add and how do you know when it will be pH 10?
3. Why is it alright to add distilled water as you do the titration into the titrant? wouldn't this dilute the titrant and affect the results?
Hi Robin.
To answer your questions:
1. Yes, the experiment should work with milk, the proteins and fat in the milk may add some challenges to the analysis, but overall it should be possible. The challenge will be getting an accurate result, to that end you may want to look into how "standard addition" methods are done to account for the matrix of a sample like milk.
2. The amount of buffer is largely dependent on the amount of acid that has been added to the solution for dissolution of sample/standard. If you know the concentration and volume of the acid added it's pretty easy to figure out how much buffer to added to adjust the pH to where you want it. It also helps that the buffer will (when in excess of the amount of acid in the solution) maintain a pH near that that the buffer had initially, so if you make a buffer with a pH of 10, the solution will end up at a pH of ~10. Alternately, using a piece of litmus paper will quickly tell you the rough pH.
3. Adding distilled water does dilute the solution, but in the end the calculations that you are making are of moles of calcium and moles of EDTA (a 1:1 ratio). Adding more distilled water doesn't change the number of moles of calcium or EDTA, so you don't change volume of titrant (i.e. number of moles of EDTA) needed.
Put 1ml of sample in the flask
Add 2 drops of NaOH
Add some drops of meroxide
Titrate with trilion B
Is that right this way?!
Anyone have the results for this experiment? I am not sure mine is right. I used Rain, Drinking, and distilled water.(Different brands of drinking water)
a question asked in jee mains 2024 about this and i had no clue what the complex formed would be gained -1 i believe
Hey! I have a question that how much volume of solutions did you add? I have to perform it in school and I have no idea. Actually I am going to compare different calcium supplements. It would be of great help if you answered.
The volumes that are added all depend on the concentration (or number of moles) required for the reaction(s). There's no fix amount that needs to be added, and it will very much depend on the amount of calcium in the supplements you are analyzing, and the concentration of your EDTA titrant.
Good luck.
@@crharrison thank you so much! You are a real life saver.
is the ammonia you used 0.88 ammonia solution and could you explain why it is crucial for the solution to be alkali, thanks great video
We use the ammonium hydroxide to keep the solution in the proper range to allow for the complexation of the calcium ions by both the EDTA and the indicator. In this instance, 2 mL of 6 M ammonium hydroxide was used.
Thanks this helped a lot man
Can I use this method to determine the Calcium content in Milk?
yes you can
To my understanding, you should be able to titrate milk directly with EDTA and determine the calcium within as a result. However, you still need to do some adjustment of the sample before you can titrate it; the pH of the milk needs to be adjusted (ideally buffered) to about pH 10. If the pH is too low the EDTA and eriochrome won't bind the metal; if the pH is too high the calcium may be precipitated as calcium hydroxide. If you adjusted the pH properly I'm unsure what could have gone wrong.
thankiuy I'm sint is Md zaid hassan
actually forward titration does not work very well. it is better to add excess EDTA (Ca content of powdered milk is ~1% by weight), let it sit for a while for the EDTA to have time to extract and bind all the protein bound Ca and then back titrate with Ca. You can also precipitate all the protein out by curdling it by adding acid, decanting/filtering and titrating the protein free filtrate.
@@PurnenduD13 Thank you for the guidance.
@anahmar89 Une de mes amies au Faculte Saint Jean a l'Universite d'Alberta etait en trains de les traduir, je ne sais pas si elle les a finis a ce point. Je m'excuse pour ne pas les traduire moi-meme, mais j'ai jamais appris la vocabulaire scientific en Francais.
Please explain me why you added water to erlenmeyer when you were doing titration? Was it not change the consentration? Im sorry my english is not good..
+Aghnia Maraya the water doesnt do anything, probably just adds to the volume to make it easier to see. Adding water would not change the calcium concentration anyway so it would not affect the end point.
+Z33NY oh i see. thanks for the answer :)
+Aghnia Maraya np lol! always better to understand than memorize i always say.
Hello, it is quite a old video but sorry. Can iron be figured out in a Iron-EDTA titration? Is there such a thing? Thanks
+Thirukumaran Kamaraj I'm not sure that iron could be effectively titrated with EDTA, though it may be possible. My big concern is that for this titration we are working around pH 9-10, which is too basic for iron and it would precipitate as it's hydroxide.
Is it possible to deduce calcium ions in milk with EDTA and eriochrome black T?
It may be possible, I have never tried it. One challenge may be that the pH of the analyte solution (the milk) will need to be adjusted to between pH 9-10, which may cause the precipitation of some of the proteins. But it could be a neat test to try.
all i know is you gotta record how much EDTA it takes to titrate a couple of mls of it, you can then say that their molarities are equal at that point.
hey, I just wanted to ask how would I prepare a 0.1 or 0.5 M of EDTA?how much powder do i put and how much water do i put
It all depends on the volume of solution you want to have, the concentration of the final solution, and the molecular formula of the EDTA that you are working with. So it's not really something I can answer, and it kind of seems like a homework question to me anyway.
Hahaa I did this last thursday and went fine :) Maybe too much indicator though, but titration was succescful!
Hi. Does water pH affect hardness? For instance, changing from 7.5 to 6.5 or 9.
The pH should not directly impact water hardness, as water hardness is the result of dissolved calcium and magnesium ions. So unless the pH is so high that those precipitate there should be no change in water hardness with pH. However, when it comes to measuring water hardness with EDTA, the pH (and proper control thereof) is crucial, due to how EDTA is able to chelate (complex) the cations (Mg2+ and Ca2+).
Thank you
@superdenj The analysis should work for lead and many other metals. There are however, some considerations that need to be taken with respect various aspects of the analysis (e.g. pH, indicator, use of magnesium...). You should be able to find a procedure on-line relatively easily. So to answer your question, the analysis with EDTA as a titrant would work, though this exact procedure may need some modification.
Prior to adding EDTA, my solution was already blue. Any suggestions for corrections which need to be made?
I'm not sure why this is happening, though two options come to mind. Either the pH is too low, or there may be too many other metal cations in the solution, outcompeting the calcium for binding with the indicator.
crharrison Thank you very much. Is there any way that I can determine if my pH 10 buffer is at the labeled pH and hasn't started to deteriorate?
how to calcium test of milk powder
Mostofa kamal
Hi what is the titrant in the burrete? thanks
The titrant is EDTA.
I made a buffer solution with ammonia solution and solid ammonium chloride, but when i tested it through Eriochrome Black T indicator( in ammonia), it turned green. I am confused as to why it is green
I'm not quite sure why you got a green color. It seems that when the indicator is free of all metals it does have a very light blue-green color: www.canterbury.ac.nz/media/documents/science-outreach/calcium.pdf
In our analysis we always have some magnesium present (in the EDTA titrant) and that may limit the ability for the indicator to go so greenish, even when we pass the endpoint. But other than that I'm stumped as to why yours went green.
@superdenj I don't believe that one can post links through the comments, so just google the following: edta, lead, titration
Good luck.
How much ammonia was added please answer crharrison please
Shashank Parsewar 2 mL of 6 M ammonium hydroxide was used.
What is the colour of Ca-EDTA complex?
The complex is actually colourless. The colour that is seen in the titration is due to the indicator (Eriochrome Black T), which changes colour based on the cation that it complexes.
@@crharrison thx sir
What was the concentration of EDTA used? and also how many moles (concentration) was the buffer?
The EDTA is about 0.02 M (though you need to calibrate it). We have been adding about 5 mL of 6 M ammonium hydroxide to the solutions just prior to titration.
@@crharrison Was there any NaOH in the edta solution. Other lab reports are saying that edta must contain NaOH and others say it shouldn't so im a bit confused.
@@thebrownzetsu7835 Yes, a small amount of ammonium hydroxide is added to the titrant. This may or may not be necessary, the key with EDTA complexations is to have a sufficiently high pH. When titrating calcium you want the pH to be around 9-10 so that the EDTA is sufficiently deprotonated to complex the metal, but that the solution isn't so basic as to form insoluble hydroxide species with your metal(s).
What was the concentration of EDTA solution? And how did you dilute this in water? I’ve been trying to make 0.1 M EDTA to titrate 25 mL and the powder is not dissolving. PLEASE HELP
EDTA can be a pain to dissolve. The best results are achieved when using the disodium form of EDTA, but even then it can be a slow process. If you don’t have the disodium for you may be able to speed the dissolution by dissolving it in a solution of NaOH. You’ll have to do some calculations to figure out how much base to use, but that should help.
crharrison thanks for responding, in this case, what was the concentration for EDTA and how much base was used in it?
@@paigela5780 We use the disodium form, and make a solution of 0.02 M. I don't have any experience in using base to help solubilize EDTA, but in theory it should work, as you can simply neutralize a few of the acidic protons with the NaOH, resulting in what is effectively a sodium form of EDTA. You'll just need to do some calculations, paying attention to the stoichiometry, to determine how much base you will need, depending on the amount, and type of EDTA you are using.
That's unfortunate that it did not work. One reason the experiment can fail is if the pH of the solution is not correct for the indicator and EDTA. With this experiment the pH ideally should be between 9 and 10, a pH below this will likely cause the analysis to fail.
One very last question: How was the calcium solution produced?
We dissolve the sample (typically calcium carbonate) in hydrochloric acid (10 mL of 6M). After dilution of the sample in a volumetric flask, we add 5 mL of 6 M ammonium hydroxide to each 10 mL aliquot that is titrated. The EDTA is also prepared with some of the ammonium hydroxide as well, to ensure the pH is in the 9-10 range.
can you email me the complete procedure for this experiment.
I'm actually a ventriloquist, chemistry is my hobby ;-)
There is no way to answer your question in 500 characters. Fortunately, there is Google that can help you. I suggest that you search for: calcium, EDTA, milk and titration. You'll be able to find plenty of procedures published by universities that will help you out.
Why at endpoint colour is blue?
When the indicator, eriochrome black T, does not have any metals to complex, it changes from red to blue.
What is DI water?
Deionized water.
How much buffer is required? Is 5ml of pH 10 buffer sufficient?
That sounds reasonable. In part it depends on the concentration of the buffer, and the change that will occur as you go through the titration. But as a starting point that seems likely to work.
@@crharrison Oh alright thanks. I've also noticed a lot of procedures require acids and bases to dissolve a solid. Currently I'm testing the affects of calcium content in kale under different cooking times. To extract the calcium, would I need to dissolve the the kale in dilute HCl or something along those lines?
@@harryxu1162 Yes, sample preparations can be rather tricky. The analysis demonstrated in this video is for the analysis of a calcium carbonate and salt mixture. Doing an analysis of kale would be more complicated. Crushing or grinding the leaves, and then dissolving them in HCl would likely be a good start. Just keep in mind that if you are using EDTA as a titrant you need your solution to be around pH 9-10 when the titration takes place, so you may need to add more base or buffer to your sample following the dissolution. The other complication could the natural dyes in the leaves. The green color will likely persist, in which case you may find the endpoint very challenging to determine.
@@crharrison Alright, thanks a lot!
Is it possible to use stoic to calculate the calcium content of my kale? So far my procedure involves grinding the kale and boiling it for a certain time length. Taking the kale solution I mix it with 20ml of DI water and 10ml pH 10 buffer. Eriochrome black T is then added and I begin my titration with EDTA.
Watching it in 2024 😅
Si quelqu'un peut m'expliquer la manipulation en français ?
why do we need to buffer the EDTA at pH 10 ?
Because at pH 10-10,5 change of eriochrome black T color, caused by emerging new form of indicator is the most visible.
stir bar!
It will give calcium + magnesia .
Drain...
It would have helped if you could have listed the name or shown the name of the indicator. The poor video quality doesn't help novices.
😒😒😏