The chemistry behind diapers

[redtails]

Originally Posted by Colonel Brome Teks

As the great web comic XKCD put it, sociology is just applied psychology, psychology is just applied biology, biology is just applied chemistry, chemistry is just applied physics, and physics is just applied math.

I have to say that I am more of a biology nerd though. That is probably heavily influenced by the fact that my mom has a Ph.D. in Bacteriology and runs a lab and teaches classes at a university. Understanding genetics, cells, etc. comes kinda naturally to me.

My older brother is currently planning to major in sociology right now, however.

I understand your hunger for biological knowledge, but I'm planning on doing biochemistry anyway because I don't think chemistry has a future. I mean right now, about 80% of all knowledge of chemistry is centred around processing crude oil into polymers and fuel. As soon as crude oil runs out, there's no more easy access to polymers and fuel, biology is the only thing that can fix that

Biology has always been one of my greatest passions, but sadly, there are no biological courses that interest me within 100 miles from where I live, and I cannot afford living at campus somewhere. The only answer to that was picking another course closer to home that does interest me. Thank you for sharing your story with us!

[silent deadly alchemist]

ok, ok very very impressive, as a 1st year biological and environmental/life science oriented university student at UTS im impressed by your knowledge especally for your age, at 17, id predict you to be at 11th/ 12th grade correct?

HOWEVER, one learns through his mistakes. so i think ill point out a few things yo failed to mention, mostly for the enefit of those out of the loop

1st and foremost, you forgot to include a specific defnation of the mole unit so i will if you dont mind:

mole:a mole, is a unit of pure quantity, in the case of chemicals, a mole of a subsance is defined as a set number of something. for example. the standard of the mole was set as being the number of atoms in 12g of carbon-12* this number is known as avogadro's constant. this number is approximately 6.02214×10^23 (^ meaning 'to the power of' ) n otherwords...
602,214,000,000,000,000,000,000... yeah its a big number... nd btw, avogadro's constant applies to anything, ts simply a number of THINGS atoms, molecules, photons, people MARCHMELLOWS sticks leaves, grains of salt, ANYTHING.

oh and, actually the compound of the absorbant material is sodium POLYacrylate the poly- indicating its a polymerised material.



*(carbon-12 indicating the isotope of the element. for those unfamilliar, an isotope is an element with a different number of neutrons in the nucleus of the atom. the extra/missing neutrons changes the weight of the atom, and can result in nstabilty whch n turn results in the decomposition of the atom to a more stable isotope, carbon 12 is the most stable isotope, having 6 protons, 6 neutrons and 6 electrons.)

(... O.O i just realised that the numbers of carbon 12's partiles form 666 *gasp* )

despte these and even these are done smply to point out, what you might want to , your analysis and calculations are very sound. im very impressed.

[redtails]

To Silent Deadly Alchemist

I am fully aware of the definition of mole, we did it so often in secondary school I could just as well dream about it, and it sounds like a good idea to add it to the list of definitions eventually. Although, as you predicted, that definition does not pose meaning for a very large group. To answer what I kind of already answeredL I don't know what you mean by 12th year, but I finished secondary school, graduated with chemistry, maths and biology as my major, got my diploma and I'll start my first year of college in just over a week.

You caught me with the polyacrylate though, I didn't realise that until this very moment. Although I must say it poses no difference to the calculation, the equation would just be different, add an n:
n C2H3COONa + 300n H2O ->-> n C2H3COONa ∙ 300 H2O

oh and there are more numbers like that in Chemistry :P, Carbon-12 forms 666, and gold has a melting point of 1337K, I always loved that!

[Star Child]

inst it true that a disposable can hold quite a lot more water than urine as the wee wee contains salts which affect the polymer? and also my nappies have grains of Be3Al2Si6O18 plus Al2o3 and si02 in them

[redtails]

Originally Posted by Star Child

inst it true that a disposable can hold quite a lot more water than urine as the wee wee contains salts which affect the polymer? and also my nappies have grains of Be3Al2Si6O18 plus Al2o3 and si02 in them

"Quite a lot" is overrated. only 1% of urine is usually made of urea, and the salts you were speaking of (mostly Na+, Cl-, and K+) are only present in trace amounts, unless the person is consuming vast amounts of salt. With trace amounts we're thinking 0.001% dissolved salts. Your saying is true though, a disposable diaper, just like a cloth one, will absorb less urine than it would absorb water, because (mainly) urea molecules and dissolved salts take in a lot more place than water would and eventually end up requiring much more polymer to be held in place. Conclusion: yes, you're right, diapers have a slightly lower absorbency for actual urine than they have for clear water.

Side note: older (plastic) diapers can tear when filled with clear water, because they were not designed big enough for the expansion of the polymer..

Also, the three ions you described are, in order: beryl, aluminium oxide, and sand. Why they are in there, I have no idea. Perhaps it's baby powder? Perhaps they have a nice (baby) smell? I can't answer that!

[Star Child]

no i just crushed up some Emerald, Ruby and Quartz from my collection and sprinkled it in my nappy