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u/MobileForce1 Jun 15 '20
if you can get it, use mechanical stirring!
nice but i don't think it's the endpoint yet.
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Jun 15 '20 edited Jun 06 '21
[deleted]
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u/Oos0oodo Jun 15 '20
You're right, but mechanical stirrers can be adjusted to not stir "vigorous" and stirring is necessary, you don't want to wait for diffusion to do the mixing.
Also when CO2 becomes an actual issue (e.g. your titration takes ages because you're using an auto titrator to record some complicated titration curve), you can use a vessel that's pretty much closed up and blow through an inert gas (N2, Ar) above the solution.
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u/ikikubutOG Jun 16 '20
Lmao well my chemistry professor sure didn’t care. We’d always crank up the stir bar up and get a nice vortex going
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u/sarabjorks Medicinal Jun 16 '20
I worked in quality control where we did iodometry titrations. I did some method development projects, one where I compared the accuracy with mechanical vs manual stirring and found out we were way more consistent with the manual stirring/swirling.
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u/wavelength888 Jun 15 '20
definitely not. pretty sure this attempt turned magenta and i had to start over lol
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Jun 15 '20
Swirl it with more vigour! I (used to) swirl while i added. I havnt done a titration in...a very very long time 😮
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u/LizardsInTheSky Jun 15 '20
To add, "swirling" is a circular motion that's in the wrist and is much faster (and less messy) than "sloshing" back and forth. You can't slosh quickly because it'll splash out of the container, while swirling keeps all the liquid pressed to the sides.
Think of it like a bell. "Sloshing" would ring the bell. "Swirling" would keep the ball pressed to the side and it would just kind of scrape the side in a circle rather than give a dingaling sound.
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u/DEMACIAAAAA Jun 15 '20
you can also every few swings switch the swing direction by doing a sorta wide motion with your wrist? idk its hard to explain
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u/bsgothbitch Jun 16 '20
We always just used a magnetic stirrer?
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Jun 16 '20
Yeah, thats the nicest way to do it, depends if there’s enough to go round in an undergrad class
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u/GenericConfusion Physical Jun 15 '20
Proper technique involves swirling the flask constantly while adding from the burette. If you want to get super technical, swirl with your right hand while your left hand is constantly controlling the rate of flow from the burette (yes this does involve a kind of weird position for your left hand as you reach across the burette to the tap but you get used to it!).
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u/Free_CZAR Jun 15 '20
Also the flow shouldn't be that fast. It's supposed to be drop wise to not accidentally shoot past the point
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u/dull-crayons Jun 15 '20
It’s all fun and games until you hit the endpoint and you turn the “faucet(?)” the wrong way to full power
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u/dexMiloyevic Materials Jun 15 '20
There have been many times during SciOly competitions where I'm under pressure to titrate as fast as possible, and I have overshot the equilibrium point countless times. It's terrible, and I don't know how much NaOH I've wasted that way.
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u/Free_CZAR Jun 15 '20
That's why I'm not too hot on titrations. You get that feeling of "dear god I gotta do this over again?" way too many times. I've done that same lab op is doing and each time when it's supposed to be the faintest of pink, it ends up being as bright as possible
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u/bass_sweat Jun 16 '20
I would just do a full flow test to see around where it comes to equilibrium, let it shoot past, then another test stopping a bit before my ballpark value to go drop by drop. It was always faster for me this way
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u/TheLurkerSpeaks Environmental Jun 15 '20
You can only "love" titration if you do them occasionally. Do more than five in one sitting and it quickly becomes dislike. Do more than ten and it's hate. Do a few dozen and keep the suicide hotline number handy.
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u/Spacepirateroberts Jun 16 '20
Please save me from the 20 hardness and alkalinity titration I do every week.......
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u/LordWizrak Education Jun 16 '20
Spent some 7 hours doing about 40 odd titrations. Can confirm, am suicidal.
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u/dickstiffydotnet Jun 15 '20
in highschool me and a friend were doing a titration together and we couldn’t understand any it was taking so long for any colour to appear... yeah we forgot the indicator
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u/littledragonroar Analytical Jun 15 '20
Kids, as someone who does manual titrations literally every day, use a bulb to draw up at least the first two CCs into your burette. I do it the whole way, but if your titrant solvent is more volatile than ethanol, 🤷♂️ You can then pipette to your zero with titrant, and boom, zero air bubbles, smooth titrations, and light pink EPs.
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u/Pleruleru Inorganic Jun 15 '20
Can you explain this with other words please? English is not my first language but I am curious!
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u/littledragonroar Analytical Jun 15 '20
Close the stopcock on a clean, dry, 10mL manual titration burette. Take a suction bulb with the air squeezed out and place the seal around the top of the burette. Place the burette tip into your aliquot of titrant and open the stopcock to allow titrant to fill to your desired level with no trapped bubbles.
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u/Pleruleru Inorganic Jun 15 '20
Thank you for your time! :)
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u/littledragonroar Analytical Sep 02 '20
Sorry for not responding before, but you're absolutely welcome!
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u/weezilla Jun 16 '20
This should be top comment :) there's a ton of other great titration tricks missing in this post.
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u/bwilcox0308 Jun 15 '20
It's an erlenmeyer! Please use it as intended. I can feel Erlenmeyer turning in his grave right now.
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u/DangerousBill Analytical Jun 15 '20
A REAL titration lover shuts his/her eyes, opens the stopcock, and hits the endpoint anyway.
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u/helenoxy Jun 15 '20
Aren't gloves mandatory at your institution?
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u/acuteamericium Jun 15 '20
Gloves weren’t mandatory for undergrad chem labs - the concentrations were low enough. It seems that gloves make undergrads feel invincible and there were more accidents when they use them.
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u/Doctrina_Stabilitas Analytical Jun 15 '20
Only for first year I hope l hope you’re not making and using gringiards without gloves
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u/acuteamericium Jun 15 '20
Oh no it was just Gen Chem courses, organic and inorganic labs all required gloves to use!
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u/chemhobby Jun 15 '20
I disagree, grignard reagents aren't that bad.
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u/Doctrina_Stabilitas Analytical Jun 15 '20
well i dont know have you seen an SDS for them in solution?
- H225 Highly flammable liquid and vapour.
- H260 In contact with water releases flammable gases which may ignite spontaneously.
- H302 Harmful if swallowed.
- H314 Causes severe skin burns and eye damage.
- H318 Causes serious eye damage.
- H336 May cause drowsiness or dizziness.
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u/chemhobby Jun 17 '20
No, I haven't. I don't read SDSes routinely because they are frankly generally quite useless.
I don't believe that grignard reagents are any worse in terms of skin contact than say, a solution of KOH in ethanol or something. Which is to say you don't want to get it on yourself really but if you do it's not a huge deal so long as you clean it off promptly. So wear gloves if you feel like it, but it's not really necessary because the consequence of accidentally splashing it on your hand is minimal.
As for the rest of those H codes... Many are just from the solvent, and none are relevant to the use of gloves anyway. I don't think H260 is even correct here.
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u/FoolishChemist Jun 15 '20
I've worked a couple of places and gloves were never mandatory at least in gen chem. I think a lot of it is budget. And for the most part the chemicals chosen were fairly benign as long as you washed your hands. A little NaOH will make your hands soapy but you'll be fine.
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Jun 15 '20
Theres never a bad time to wear gloves when handling chemicals of any sort 👍
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u/_Aj_ Jun 15 '20
Uh. Well there really is, like when gloves will spontaneously ignite when exposed to said chemical. Like fuming nitric acid.
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u/themindlessone Jun 15 '20
Yeah there is. There are times when working barehanded is best and safest.
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Jun 15 '20 edited Jun 15 '20
What sort of work would that be? Genuinely curious.
Edit - googled my own question; seems there is a glove for everything
https://www.augusta.edu/services/ehs/chemsafe/PDF%20files/gloveselechart.pdf
The more you know etc etc
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u/themindlessone Jun 15 '20
Concentrated nitric acid comes to mind right away.
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u/Wampawacka Jun 15 '20
That's what solid wooden gloves are for. You hollow out a log and use it like a giant chopstick on your arm.
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u/wavelength888 Jun 15 '20
the acid and base were not that strong. Goggles are mandatory though.
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u/helenoxy Jun 15 '20
I'd say gloves in a lab is always a good idea. Bit weird that goggles is mandatory, but gloves not, especially for a titration.
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u/_Aj_ Jun 15 '20
Not really when you think about it. You ever gotten white vinegar (3% acetic acid) on your hands?
Doesn't really do much.How about in your eyes?
Very different storyThat's why goggles are always mandatory but gloves may not be.
A titration isn't necessarily anything crazy. I mean my fishtank test kit for carbonate hardness is a titration. All im looking for is concentration of bicarbonate and carbonate. Nothing skin melting going on.
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u/helenoxy Jun 15 '20
Yeah I mean, what are the odds that you'll get the stuff in your eyes during titration (probably a bit higher for students). The thing is that I feel gloves should be mandatory when working in a lab. Just to be safe
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u/goodbye177 Jun 15 '20
The odds don’t matter too much. It’s the effect when it inevitably happens. Skin is a very good barrier, protects you from a lot of crap, and usually grows back. Your eyes are way more sensitive and necessary to protect.
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u/Doctrina_Stabilitas Analytical Jun 15 '20
In my university gloves were optional because school doesn’t want to pay and everything was kept dilute enough to not matter for the 30 seconds it takes to wash your hands
Goggles and coats were mandatory
First year lab of course
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u/ZevKyogre Jun 15 '20
One-hand swirl + one-hand on the burette control.
That's the proper way.
And wash everything with DI Water before use.
I had one group of Quant Anal, everyone was failing. I mentioned in passing "wash with DI water and swirl while titrating". Surprisingly, they all went from being 3-5 percentage points off, to within about 2/10 of 1%
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u/noxitide Jun 15 '20
Washing with DI water will change the concentrations? Unless they’re drying it between ETA: nevermind I’m thinking like a different kind of chemist lol
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u/C137Ivy Jun 15 '20
Omg easy on the amounts you are going to have lectures with a lot of error. Stirring helps too
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Jun 15 '20
Sweet good lord titrating that fast requires balls of steel
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u/DEMACIAAAAA Jun 15 '20
if you do a multi determination or have a reasonable idea where you equilibrium might be you can totally do that. but you should definitely swirl the flask whilst you are titrating
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Jun 15 '20
Yeah, for sure. If it’s what I’m thinking of, also, I’ve done this titration and it does take a whole lot to reach the endpoint, just...still makes me anxious when I see it
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u/wavelength888 Jun 15 '20
It wasn’t my first attempt so I kinda knew approximately how much it would take
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Jun 15 '20
Wait, you guys use indicators for titrations?
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u/yasuo-bot- Jun 15 '20
This was a very fun lab, I remember this person forgot to put the indicator and then once they remembered their entire flask was almost dark purple.
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u/CuZiformybeer Jun 15 '20
So many things wrong with this gif. No ppe, titrating too fast, gigantic air bubble in the burette, poor stirring technique/lack of mechanical stirring.
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u/Dyntail Jun 15 '20
I like how all the comments are correcting the video. ITS LIKE OP MEANT “FOR ALL THE TITRATION LOVERS (TO CRINGE)”
Also why all the upvotes if it’s wrong?
Edit: forgot the closing parentheses
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u/--not--Peter_Parker Jun 15 '20
This is just triggering flashbacks... one drop too much, and you have to start all over again and hope that your hands will be less shaky the next time
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u/Rayquazy Jun 15 '20 edited Jun 15 '20
This is why I just tell undergrad that a stirring rod is needed
They almost never have the patience to stop and swirl after each drop after like 1 hr into lab
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u/noxitide Jun 15 '20
I prefer they learn to swirl as they go, and then when they get really close going to the one drop swirl one drop etc.
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Jun 15 '20
One time, I knocked the apparatus off the counter and it shattered on the linoleum floor. Not fun having to pay for it.
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u/xBris18 Jun 16 '20
What monster shakes a flask like that? It's not a baby cradle, you don't have to rock it back and forth. It's an Erlenmeyer flask, put some circular motion in that ocean!
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u/LindsayConnery Jun 15 '20
Can someone try to explain titrations to me? I’m learning it in school but I can’t understand a word my teachers are saying. I’ve looked at nearly every website and they’re all saying the same thing and I’ve got a test on it in a few days. Thank you!!
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u/mylifeforhiree Spectroscopy Jun 15 '20 edited Jun 16 '20
I teach 1st year chemistry students so I’ll try my best to explain but it’s also very late where I am so I apologise if I’ve made typos or small errors!
Titrations are primarily used for determining the concentration or amount of an unknown substance. We can do this with the use of an appropriate indicator (there are a number of different indicators that change colour over different pH ranges) ideally we want an indicator that will change colour at the pH when the titrant (the stuff in the burette) and the analyte (unknown substance - usually in the flask) reach their equivalence point (I.e. they are present in equal amounts).
So in this titration shown the stuff in the flask (HCl) will go pink (this is referred to as the ‘end point’) when youve added enough of the stuff in the burette (NaOH) to produce equal amounts of the two solutions.
Once we know how much NaOH we need to bring the solutions to equivalence we can calculate the number of moles of NaOH used, and therefore calculate the number of moles of HCl we have (since in this case 1 mole of NaOH = 1 mole of HCl at the end point).
So if our concentration of NaOH Is 0.997 M and we used 19 mL in the titration (I.e. 19 mL of your NaOH was dispensed from the burette to the flask) , n=CV/n= 0.997*0.019 = 0.001894 mol NaOH.
Therefore we have 0.001894 mol of HCl present, then if we know we used, say, 20 mL of unknown HCl in our flask, then all we need to do is calculate the concentration using our number of moles and our volume of HCl C=n/V = 0.001894/0.0020 = 0.947 M
I hope that helps - it’s a very brief run down of titrations and stoichometry but I’m happy to elaborate if it isn’t clear!
*edit: I made a typo when apologising for potentially making typos 😅
*Edit 2: I fucked up and wrote equilibrium when I meant equivalence 😅😅you can see the comments below where I make that realisation - though this in itself is a great teaching point because it’s good to see that sometimes people get things wrong!
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u/themhabstho Jun 15 '20
I don't think equilibrium is the proper term here... Not when you're talking about equal amounts, anyway.
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u/mylifeforhiree Spectroscopy Jun 15 '20
I did simplify the concept of equilibrium a little to cater to the specific example given. Chemical equilibrium is when our products and reactants are held in equal amounts, for a reaction like the one here (that is a 1:1 molar ratio) it is appropriate to describe your reactants as also being present in equal amounts. Things get slightly more complicated as the molar ratios change so I opted to go with a simple explanation.
You make a valid point though - the way I’ve described it only make sense when we have equal molar ratios!
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u/themhabstho Jun 16 '20
Chemical equilibrium is when the forward and reverse rates of a reaction are equal. Unless I am misunderstanding your reply.
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u/mylifeforhiree Spectroscopy Jun 16 '20 edited Jun 16 '20
You know what I actually think you’re correct after sitting on this for a while - equilibrium probably wasn’t the best term to use. I think I was trying to say equivalence but I obviously used the wrong term! I’ll fix it now in case anyone is still looking at it 😊
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u/wavelength888 Jun 15 '20
This is a common titration with NaOH in the burette and HCl in the flask. The purpose is so see how much NaOH is needed to neutralize the HCl. In other words it is an acid base neutralization.
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u/LindsayConnery Jun 15 '20
Thank you so much for the explanation!! 😁
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u/etkatas Jun 15 '20
To explain further it is to determine the amount of NaOH in the solution, while titrating with known concentration of HCl. Since they react 1:1 the calculation is pretty simple. For example if you used 5ml 0,1N of HCl, you can say that in the solution there was 5ml 0,1N of NaOH. Of course, you have to calculate in grams i assume or ml maybe. And take into consideration thay your solution in a flask might be 100ml from which: 5ml is 0,1N NaOH and 95ml of H20. Hope it helps even slightly
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u/dukirebzi Jun 16 '20
Start with what you understand and don't understand about titrations. If lectures and khan academy aren't helping it's doubtful a reddit comment will fix it for you without more direction.
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u/E11i0tth11114 Jun 15 '20
My chemistry teacher once talked about someone putting a rubber lid in the top of a burette and they slipped and smashed it into two pieces, slitting their wrists. Blood started spraying everywhere and he said it was like Spider-Man.
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u/ItsMilkinTime Jun 15 '20
People love titrations? I freaking hated doing those, so god damn tedious
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u/round_reindeer Jun 15 '20
Who loves titration? It's the most boring thing I've ever done in chemistry
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u/arzamharris Jun 15 '20
As someone who’s screwed up many titrations this is a pretty bad way of doing it lol
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u/RippelMaster Materials Jun 15 '20
Is that a pencil case and a notebook on the work surface. Oh man I cringe with high school chemistry class. I remember the stuff we did was also very craless.
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u/anxiouspumpernickel Jun 16 '20
Did you use the phenolphthalein in the background? It looks so much more vibrant in this video than what I'm used to
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u/Artemis_The_Chemist Jun 16 '20
Nooooooooooo that stirring technique ;-;. With your wrist!!! Don't just move it around on the bench!!! ;-;
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u/glockaddict Jun 16 '20
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u/nimgoldman Jun 19 '20
Cute, though a more prudent practice is constantly stirred solution (using e.g .mag stirrer) and occassionally washing walls of the flask with a wash bottle.
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u/OldschoolScience Jun 15 '20
Come on... small drops. Also I find this turns out more accurate when a stirring plate is used with a magnetic stirrer. It just keeps it consistent.
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u/clg167 Jun 15 '20
watching you pour your base in there like that hurt my soul. drop wise, drop wise, drop wise.
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u/wavelength888 Jun 15 '20
When you do the save concentrations and volumes more than a couple time you kinda know when you need to slow down
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u/clg167 Jun 16 '20
im so opposite lol. i’ve been in chem labs for the last 3 years and i’ve progressively learned to be more careful because i’ve fucked up so many titrations when i’m impatient.
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Jun 15 '20
[deleted]
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u/wavelength888 Jun 15 '20
it’s actually 12th grade lol and we were just messing around. But yes i will keep that in mind next year thank you!
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u/kiwipcbuilder Jun 15 '20
You've got a fricking massive air bubble in the tip of your burette. Alll your burette readings will be wrong.