I'm not a chemist - help Mr. Wizard.

alanrockwood · Jan 25, 2009

Just a quick comment about polynomials: It is known that polynomials can sometimes show pathological behavior when fitting certain kinds of data. For example, a polynomial might go through every point in a data set but have wild swings between the data points that do not accurately represent the underlying function being fitted. This sort of thing tends to be more common when using high order polynomials, and if I am not mistaken experimental data, which generally contains noise, is likely to accentuate this problem.

Pade functions are another option for parameterizing data. Pade functions often work better than polynomials of comparable complexity in the sense of providing a smoother fit or interpolation as well as providing a better extrapolation outside the fitting range.

For all you non-geeky people, sorry for the geek talk, but for us geeks this sort of thing is fun.

Kirk Keyes · Jan 25, 2009

Remember, I'm plotting g/L vs. sp gr.

I get a r=0.99997175 plotting the silver nitrate data this way, including the 4Molar value. That seems linear enough to me. Maybe not for Kodak?

Incidentally, you do mean Molar by M? Molal, used to be "m", but I guess now it should be mol/kg.

Photo Engineer · Jan 25, 2009

IDK why Pade functions were not used. I do know that what we did was accurate to 1% or better. Usually, we relied on them to 4 decimals. The data was very clean without much scatter. The curves did go through swings as illustrated in one of the references cited above with positive and negative slopes. So, this might be part of it. The value I gave as 4M is Molar. I spell out Molal as I used it so seldom except in certain corrections for kettle dilutions.

In addition to these models, there was one for AgBr, one for AgI and one for Gelatin. These 3 were simply derived from handbook data and worked very well for us. The others were not usable due to errors "here and there" in the concentration ranges we used.

PE

Ray Rogers · Jan 26, 2009

Kirk Keyes said:
Ray, I'm sure Dr. Spock could explain all about bottle feeding and diapering one could ask for, but I suspect you are referring to Mr. Spock...

Yes. While it may be spooky to think there were two Dr. Spocks, our Dr. Spock was technically a Dr. (as in Ph.D.); I believe he received his doctorate in Applied Computer Algorithmic Physics from the Daystrom Institute and another doctorate in Quantum Astro-Physics from the Star Fleet Science Academy. Furthermore, I think he was awarded an honorary Doctorate in Human Psychlogy by some small institution. The reason he is always referred to as "Mr." is because in a military setting you are referred to by rank rather than honorifics and Doctor would not be appropriate while Mister, Captain or Ambassador would be.

Or so I hear. Anyway, I understand he has a fancy for photography.
Perhaps he will join us here and explain it himself someday.

Oh and Kirk- Yes! Physical constants would be very good information to have all in one place!

Ray

Dan Dozer · Jan 26, 2009

Pycnometers, molality, and polynomials - OOOOOHHHHH - my head hurts. I can't even pronounce some of those let alone understand what it all means. Who would have thought that my original question would have generated all this.

I'm glad all you chemists and mathematicians out there are enjoying all this. Keep it up and have fun - even if I don't understand it.

Dan

Ray Rogers · Jan 26, 2009

Dan Dozer said:
Pycnometers, molality, and polynomials - OOOOOHHHHH - my head hurts. I can't even pronounce some of those let alone understand what it all means. Who would have thought that my original question would have generated all this.

I'm glad all you chemists and mathematicians out there are enjoying all this. Keep it up and have fun - even if I don't understand it.

Dan

Dan, you are not alone. I am sure a lot of us do not know what we are talking about, and I am a prime example. But you see, I really want to learn. I need to learn and math is what ate me alive years ago.

As for your question, you did get an answer - from
the first person to respond... Dana Sullivan.
Everything that followed was extra

One problem is that there are several ways of doing it... and no they were not really addressed, but I think that is in part because the first answer was close enough.

Anyway, Did you get the answer you needed?

If not, give it another try. I am sure someone here can give you a clear answer.

Ray

Ray Rogers · Jan 26, 2009

Ray Rogers said:
One problem is that there are several ways of doing it... and no they were not really addressed, but I think that is in part because the first answer was close enough.

See

http://www.uab.edu/clabsc/solution.htm

for examples... I only glanced at it but it may be of help....

Ray

Photo Engineer · Jan 26, 2009

Ray, Dan;

Unfortunately, Dana's answer was ambiguous. She said in effect, 5 grams of solid in 100 ml of liquid. This could mean either total volume of solution or in 100 ml of solvent. If she had said 5 grams of solid in 100 ml of solution then it would have been unambiguous.

Following comments further confused the issue.

And then, as Kirk noted, someone asked "why".

PE

dwross · Jan 26, 2009

dwross said:
For less than 10% solutions, I add 10g to 100 ml water. For 10% and greater, I bring the solution up to 100 ml.
Denise

I've missed the window of opportunity to quietly edit this little gem of a typo, but I can't let it stand. In an attempt at brevity, I left out a clause that makes it clear that for < 10% solutions, I add the % solute in grams to 100 ml of water (i.e. a 2% solution would be 2 g in 100 ml water.) I was more clear in a subsequent post, but I can't let the oops stand.

Kirk, if this was what you were referring to, I shouldn't have snarked at you. I owe you a beer for that one.

d

Ray Rogers · Jan 26, 2009

Photo Engineer said:
Ray, Dan;

Unfortunately, Dana's answer was ambiguous. She said in effect, 5 grams of solid in 100 ml of liquid. This could mean either total volume of solution or in 100 ml of solvent. If she had said 5 grams of solid in 100 ml of solution then it would have been unambiguous.
PE

Ron,
I know it was ambiguous; but in my opinion, it is slightly less ambiguous than the other way of saying it incorrectly.

In any event, there are those amoung us who feel it doesn't really make that much differance and frankly, for those people, considering their goals, it probably doesn't, or at least it might go unnoticed. With that in mind, I am willing to let it go. Besides, Dan might have interpreted it correctly anyway.

Ray

Ray Rogers · Jan 26, 2009

Letting the oops stand...

dwross said:
I've missed the window of opportunity to quietly edit this little gem of a typo, but I can't let it stand. In an attempt at brevity, I left out a clause that makes it clear that for < 10% solutions, I add the % solute in grams to 100 ml of water (i.e. a 2% solution would be 2 g in 100 ml water.) I was more clear in a subsequent post, but I can't let the oops stand.
d

Denise,
I knew what you meant, or I was confused.
Which is kinda the same thing:

Best wishes...

Ray

Dan Dozer · Jan 26, 2009

Ray Rogers said:
Dan, you are not alone. I am sure a lot of us do not know what we are talking about, and I am a prime example. But you see, I really want to learn. I need to learn and math is what ate me alive years ago.

As for your question, you did get an answer - from
the first person to respond... Dana Sullivan.
Everything that followed was extra

One problem is that there are several ways of doing it... and no they were not really addressed, but I think that is in part because the first answer was close enough.

Anyway, Did you get the answer you needed?

If not, give it another try. I am sure someone here can give you a clear answer.

Ray

Thanks Ray - Yes, Dana gave me the exact answer I needed. I thought this thread would ended there, but obviously, it attracted a lot of other attention.

Kirk Keyes · Jan 26, 2009

Ray Rogers said:
Or so I hear. Anyway, I understand he has a fancy for photography.
Perhaps he will join us here and explain it himself someday.

I have a chance to buy some of Mr. Nimoy's nudes once. Not my cup of tea. From the prints, it certainly looked like he knew how to handle a camera.

It would be interesting to have him here, but I suspect he's too busy making retread movies these days. (Or is that "reboot"?)

Kirk Keyes · Jan 26, 2009

dwross said:
Kirk, if this was what you were referring to, I shouldn't have snarked at you. I owe you a beer for that one.

Denise, I'll take a root beer!

RobertP · Jan 26, 2009

Dan, Sorry I didn't mean to confuse the thread. I was the one asking for exacting language and technique. I have seen numerous instructions posted as "how to" mix solutions, where they say for a 10% solution add 10 grams to 100 ml of H2O and then you end up with more than 100ml of solution. For the non-chemist this type of language can lead to confusion. For a novice it would be much easier to instruct them to start with less H20 and then add more at the end to bring it up to 100 ml of solution. A technique that a chemist probably takes for granted as a proper way to mix. But I must say the conversation it triggered has been very interesting. Robert

Ray Rogers · Jan 26, 2009

Kirk Keyes said:
Denise, I'll take a root beer!

Another root beer fan?
I wish I could treat you both to some of my homegrown stuff !

Kirk Keyes · Jan 27, 2009

Hmmm... I love root beer! If I make it to Japan someday Ray, I hope to enjoy a glass of your root beer!

Ray Rogers · Jan 27, 2009

Kirk Keyes said:
Hmmm... I love root beer! If I make it to Japan someday Ray, I hope to enjoy a glass of your root beer!

OK,

Just give me sufficient notice if you want the natural fermentation version!

Ray

Kirk Keyes · Jan 28, 2009

OK - your on. But I have to say it will most likely be many years from now.

I'm not a chemist - help Mr. Wizard.

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