Mixing chemical question

[Loris Medici]

Indeed, the most complex alt-process mixing I can think of is New Cyanotype or Argyrotype. (And that's w/o having silver(I) oxide on hands...) And both are pretty easily accomplished.

Depends on which school you've attended + your personal interest to the subject then...

Regards,
Loris.



I quite liked Chemistry in high school in the US about 13 years ago now. Didn't seem too bad. I have to admit mixing photo chemicals for alt processes is easier than high school chemistry class... Don't have to write up lab reports afterwards either.

[Photo Engineer]

I think that today, the schools are more interested in protecting the students from any potential injury in chem lab than they are in teaching and more interested in sports than in science.

PE

[CBG]

Plus the students and almost everyone else in society are told that "chemicals" are dangerous. Thus people are terrified of stop bath after they enjoy their health salad.

[mpirie]

... Don't have to write up lab reports afterwards either.

When it comes to alternative photographic processes your "lab report" finds a much bigger (and some might say more appreciative :o) audience on this forum ;)

My difficulty when it comes to mixing chemical solutions was the conundrum we faced in first grade chemistry class where we took 50ml of methylated spirit and 50ml of water then had to explain why the combined solution only added up to 95ml.

Of course i know now that it's molecular size, but I wonder sometimes if this is taken into account in mixing instructions, or whether the differences are negligible?

Mike

[Photo Engineer]

Mike;

Sorry to burst your bubble but it is not molecular size that causes the "shrinkage". :(

And yes it is taken into consideration. In my above description, it is the reason why one must specify what the combined units are (wt/wt, wt/vol, vol/wt etc.)...

PE

[mpirie]

Mike;

Sorry to burst your bubble but it is not molecular size that causes the "shrinkage". :(

PE

Hi PE,

Now that my bubble is well and truly burst, what IS the reason for the shrinkage?

(I wonder if my chemistry teacher is a subscriber? :D )

Mike

[Photo Engineer]

Mike;

That is way beyond the scope of APUG (MEANING: I forget! :D )

No, actually, it is a mix of hydrogen bonding, Van Der Waals forces. http://en.wikipedia.org/wiki/Van_der_Waals_force

There are a few other things that enter into this as well.

PE

[Kirk Keyes]

Now that my bubble is well and truly burst, what IS the reason for the shrinkage?

It's because when the water and the alcohol mix, they get cold. And when things get cold, we all know there is shrinkage. Yes. Significant shrinkage! Like a frightened turtle...

(My appologies to Jerry Seinfeld.)

[Photo Engineer]

Actually, some alcohol/water mixtures warm up as does sulfuric acid/water when mixed. Some shrink and some expand depending on the forces and bonding involved.

PE

[Anon Ymous]

Since we got to temperature variations during dissolution, which chemical causes temperature to increase when mixing D76 and Xtol? Is it sulfite? I noticed a 3 degrees C increase when mixing my 5l batch of Xtol (18 -> 21).

TIA

[Photo Engineer]

Alkali generally increases temperature when mixed into water. That might be it. Sulfite does not generally increase temperature unless it is totally anhydrous. Then it might increase temp as well.

PE

[Anscojohn]

I think that today, the schools are more interested in protecting the students from any potential injury in chem lab than they are in teaching and more interested in sports than in science.

PE
******

Thank you, PE; and Steven Jay Gould; and Carl Sagan, who were saying the same fifteen years or so ago.

[Kirk Keyes]

It's because when the water and the alcohol mix, they get cold. And when things get cold, we all know there is shrinkage. Yes. Significant shrinkage! Like a frightened turtle...

(My appologies to Jerry Seinfeld.)

My post above was intended purely for some slight possible chance of humor. It is not scientifically accurate and should not be misconstrued as being on topic.

By the way, for those not in the know, here's the complete reference -

Jerry: No, I'm not gonna tell her about your shrinkage. Besides, I think
women know about shrinkage.

George: How do women know about shrinkage? (They see Elaine walking down the hall) Elaine! (She enters) Do women know about shrinkage?

Elaine: What do you mean, like laundry?

George: No.

Jerry: Like when a man goes swimming... afterwards...

Elaine: It shrinks?

Jerry: Like a frightened turtle!

Elaine: Why does it shrink?

George: It just does.

Elaine: I don't know how you guys walk around with those things.

[tiberiustibz]

Not that I understand my chemistry education but I do about van der waals and London dispersion forces and dipole dipole interactions and whatnot. Or at least I can take numbers and plug them into equations to get other numbers... yay for AP Chem.