Pyro - 20-12-2012 at 11:38
Hello,
I am wondering if there is any difference between:xOH in pearls (usually 1-2mm diameter), in pellets (usually 5-8mm) or in flakes? I have both pearls
and pellets and it seems that the pellets dissolve in water better and produce more heat.
does anybody have similar experiences?
elementcollector1 - 20-12-2012 at 11:45
That's simply due to the different processing alkali hydroxides (which I assume you're talking about) can go through. For example, my NaOH is in prill
form, while my KOH is in flake form. (My Ca(OH)2 is a fine powder, but we don't talk about him.)
Pyro - 20-12-2012 at 12:03
my NaOH is in pearl form, my KOH in pellet, but my KOH seems a lot more reactive than my NaOH. .
and I am asking if there is any difference.
kristofvagyok - 20-12-2012 at 12:12
KOH is a bit more reactive than NaOH even if they are in the same form, so this can't be compared on this way.
We have NaOH pellets, flakes and micropearls. I would say that the pears are the most "reactive", after that the flakes and at last the pellets.
Pyro - 20-12-2012 at 12:16
is there any difference in the ''hygroscopicness'' 
kristofvagyok - 20-12-2012 at 12:24
Yes. Bigger surface means bigger place to adsorb water.
Pellets have the smallest surface, after that the micro pearls and the flakes are the most hygroscopic.
I had a friend who tested highly hygroscopic reaents on a really "original" method. He got out a little of the reagent from the bottle e.g.: AlCl3,
NaOH, KOH ect. and he spit on it. If it had a sizzling sound than it was okay 
Pyro - 20-12-2012 at 12:29
yuck! he must have had good aim!
strange how it seems just the opposite to me
Oscilllator - 21-12-2012 at 19:43
surface area to volume ratio. Very important to reaction rates
EDIT: probably the reason your observing the pellets releasing more heat is because they have a lower SA/V ratio, which means they will absorb water
more slowly from the air. Therefore the pellets will likely have absorbed less water than the flakes, and thus have more heat to produce apon
dissolution.
[Edited on 22-12-2012 by Oscilllator]