Colloids

[MedPR]

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What exactly is a colloid? I've read the definition and I get that it is an "immiscible suspension" but what does that mean? What is the difference between a colloid and a precipitate?

 

[pfaction]

Based on my pharmaceutical knowledge: colloid is a very, very fine particle that forms a semi-suspension. We use sulfur colloid in radiopharmaceutics to target liver for imaging. I also used it once for bloodwork, that **** was intense. Can't be more than 10 microns otherwise the patient's veins close and then I get my pharmacy sued and license revoked by the state 🙁

 

[Temperature101]

Based on my pharmaceutical knowledge: colloid is a very, very fine particle that forms a semi-suspension. We use sulfur colloid in radiopharmaceutics to target liver for imaging. I also used it once for bloodwork, that **** was intense. Can't be more than 10 microns otherwise the patient's veins close and then I get my pharmacy sued and license revoked by the state 🙁

Are a pharmacist?

 

[MedPR]

Bump. I know the definition, I don't understand it conceptually.

 

[MT Headed]

a colloid is crap in a liquid that is remains in suspension, i.e. even when it sits in a jar for a week the crap won't settle to the bottom.

you can tell you have a colloid because of the "Tyndall effect", if you pass light through a colloid the light spreads a little and gets fuzzy. as opposed to a genuine dissolution scenario where the light will pass straight through. colloids are kind of halfway between non-suspension (like sand + water) and dissolution (like cranberry juice).

memorization tip: milk is a "cowloid"

 

[chiddler]

I think precipitate is easily separable while colloid is not.

 

[MedPR]

a colloid is crap in a liquid that is remains in suspension, i.e. even when it sits in a jar for a week the crap won't settle to the bottom.

you can tell you have a colloid because of the "Tyndall effect", if you pass light through a colloid the light spreads a little and gets fuzzy. as opposed to a genuine dissolution scenario where the light will pass straight through. colloids are kind of halfway between non-suspension (like sand + water) and dissolution (like cranberry juice).

memorization tip: milk is a "cowloid"

I wish you hadn't taken your MCAT already. I remember ~2-2.5 months ago when you had an answer for everything. Thank you 👍

I think precipitate is easily separable while colloid is not.

So if your reaction made a colloid and you wanted the precipitate, you would have to add something to precipitate out the crap in the colloid?

 

[chiddler]

I wish you hadn't taken your MCAT already. I remember ~2-2.5 months ago when you had an answer for everything. Thank you 👍



So if your reaction made a colloid and you wanted the precipitate, you would have to add something to precipitate out the crap in the colloid?

i'm thinking: a precipitate strictly means some solid is produced. is it possible for that solid to form a colloid with the liquid?

probably.

so perhaps a precipitate can form a colloid and they are not mutually exclusive.

 

[milski]

I wish you hadn't taken your MCAT already. I remember ~2-2.5 months ago when you had an answer for everything. Thank you 👍

While we're on that subject, I hope that you're still sticking around to answer my BIO questions when my time comes. 🙂

 

[MedPR]

i'm thinking: a precipitate strictly means some solid is produced. is it possible for that solid to form a colloid with the liquid?

probably.

so perhaps a precipitate can form a colloid and they are not mutually exclusive.

Thanks, that makes sense.

While we're on that subject, I hope that you're still sticking around to answer my BIO questions when my time comes. 🙂

When is your MCAT? I will do my best, afterall you have probably taken me from around an 8 on PS to whatever I end up getting. I'm finding that I enjoy helping (or trying to) with topics that I feel comfortable with so I think I'll be around for a while. I need something to do at work anyway 🙂

 

[milski]

Thanks, that makes sense.



When is your MCAT? I will do my best, afterall you have probably taken me from around an 8 on PS to whatever I end up getting. I'm finding that I enjoy helping (or trying to) with topics that I feel comfortable with so I think I'll be around for a while. I need something to do at work anyway 🙂

The current plan is for Jan/2013 and is unlikely to change. Explaining things tends to make them a lot clearer to me, I've seen that in other areas before.

Good luck in a few days, btw!

 

[MedPR]

The current plan is for Jan/2013 and is unlikely to change. Explaining things tends to make them a lot clearer to me, I've seen that in other areas before.

Good luck in a few days, btw!

Thank you!

 

[pfaction]

AAMC10 had stuff on colloids and adding a polymer to precipitate it though.

 

[folktale]

I did some EK 1001 on this and I remember it said something about particles having a larger size than the actual solvent it is suspended in.

 

[HollowSuperet36]

Yeah from Kaplan colloids are not easily separated. You cannot separate them by filtration. Generally need to add something to cause precipitate. Also second that it is on AAMC 10.

 

[MT Headed]

I did some EK 1001 on this and I remember it said something about particles having a larger size than the actual solvent it is suspended in.

Yet sucrose (FW = 20 x water) dissolves in water and doesn't form a colloid...