Page 1 of 1

I need help for this reactions

Posted: Fri Jul 08, 2022 7:16 pm
by Kali
I am not a chemist, but I would like to understand what happens in the following situation.

On the practical side, it is about the reaction of the alum with the setting stem that is stuck in the crown of the watch.
The effect is to be such that the setting stem of the watch is to break out (crumble) of the crown of the watch.
It didn't work for me, so I'm looking for the reason.
To be sure if there is any reaction in case the settings stem were made of stainless steel, I placed a nail into the alum-water solution, also without reaction. In addition, I heated the solution, also without reaction.

So I started searching and found information about two types of alum:
A. Aluminum potassium sulfate - AlK(SO4)2 (dodecahydrate x12H2O)
B. Ammonium aluminum sulfate - NH4Al(SO4)2 (dodecahydrate x12H2O)

1. And now please help me complete the equation ad.B, because this is probably my case.
AlK(SO4)2 + 3H2O → Al(OH)3 + KHSO4 + H2SO4
NH4Al(SO4)2 + H2O → ???

2. What happens if to put high-carbon steel in the solution (f.e. 1095 steel - Fe 98.38 - 98.8%, C 0.90 - 1.03%, S ≤ 0.050 %, P ≤ 0.040%)?

Thank you,

Re: I need help for this reactions

Posted: Fri Jul 08, 2022 10:25 pm
by ChenBeier
Why should it happen.
1. What is your purpose or benefit for it?
2. On the other hand alum is the wrong chemical to obtain it.
Alum is a salt what only dissociate in water, like other salt do, there is no sulfuric acid or other compounds.
3. The steel can only dissolved with hydrochloric or sulfuric and a strong oxidiser present. But this would also destroy the watch.

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 6:45 am
by Kali
I wrote what I want to achieve. Remove the broken setting stem from the watch's crown.The setting stem is to crystallize in order to be able to pick it out. Without any mechanical intervention such as drilling or cutting. I don't have the precision tools to do it this way without damaging the crown.

Apart from theoretical considerations, I saw in practice that it works. I want to understand why it didn't work for me and solve this problem.
BTW according to this chemical reaction AlK(SO4)2 + 3H2O → Al(OH)3 + KHSO4 + H2SO4 (for alum of aluminum potassium sulphate) what is the H2SO4? Isn't that sulfuric acid? Besides, as far as I know, a solution of alum with water is acidic.

After all, I do not put the entire watch in the solution, but only the crown of the watch with the broken setting stem. This steel (I note that high carbon steel, not stainless steel) is not meant to dissolve. Rather, it is supposed to crystallize, weaken, to be easily removed (picked out) with a skewer. Of course, assuming that the crown of the watch is made of a different material than the setting stem :lol:

But that's not the point. In order not to elaborate on the topic and focus on its essence, I am interested in what are the possible solutions to the following chemical reaction (for alum of ammonium aluminum sulfate - NH4Al(SO4)2 ):

NH4Al(SO4)2 + H2O → ???

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 7:18 am
by ChenBeier
To 1. You have not the right tool mechanically and also not the right chemical. It is impossible to do in this way.

To 2. The recation what you wrote goes in opposit direction.
Al(OH)3 + KHSO4 + H2SO4→AlK(SO4)2 + 3H2O
and AlK(SO4)2 →Al 3+ + K+ + 2 SO4 2-, that is the dissociation I told before.
The acidity of Alum solution comes from the aquo complex [Al(H2O)6] 3+ => [Al(H2O)5OH] 2+ + H+,
With the Ammonium salt there is no difference only K+ is exchanged to NH4+.

3. What do you mean with crystillize. First something has to be dissolved and then water evaporation has to take place until it can crystillize.

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 8:16 am
by Kali
Thank you for Your response.

ad.1 and ad.3
However, something happens that the setting stem can be easily removed by means of a solution of alum with water, for example with a needle. Maybe it's fake or some kind of magic :wink: but You can check this out on YouTube (you need to remove spaces from the web address):

before: (the problem)
www. youtube .com/watch?v=h5hoiQ45-mw&t=177s
after 1: ("crystillize", graining of the setting stem):
www. youtube .com/watch?v=h5hoiQ45-mw&t=471s
after 2: (removed setting stem):
www. youtube .com/watch?v=h5hoiQ45-mw&t=668s

And a short video (17 seconds) showing that some kind of chemical reaction is going on:
www. youtube. com/watch?v=VHrpYk7z9aU

So I don't know what to think about it :?

I do not have the necessary knowledge to argue. So I will be based on what you wrote, thank You :)

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 9:06 am
by ChenBeier
This shows only a dissolving of the stem over 10 days, there is no crystalisation. This can be done with sulfuric acid /peroxide in some hours

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 2:52 pm
by Kali
Oh, the term crystallization was unfortunate. I meant the setting stem consistency after the reaction with the solution. More like a grain.
And as I wrote before, I am not a chemist. English is also not my native language.

According to Your opinion, what concentration of the acid would have to be in order to achieve the desired effect (e.g. sulfuric acid)?
It doesn't have to happen in a couple of hours, it can be longer.

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 3:42 pm
by ChenBeier
About 20-50 g/l H2SO4, 5-8 g/l NaCl and 30-40 ml/l H2O2 30% or 50 - 70 g/l Na2S2O8, Temperature 50 - 60 °C ,
Stirring or air agitation

Re: I need help for this reactions

Posted: Sat Jul 09, 2022 3:59 pm
by Kali
Thank you very much :)


The use of acid was not necessary. The setting stem (1.5mm long) was removed and the crown survived :) It took several hours.
55g of alum (I don't know if it was NH4Al(SO4)2 or AlK(SO4)2) dissolved in water, 300ml of solution in total. The key was to heat this solution above 83 degrees Celsius. At higher temperatures, the reaction was faster. So it is possible in practice. I only hope it wasn't the composition of the water (except oxygen and hydrogen) that caused it, because I was pouring it from the tap :wink:

I am curious what it looks like from the theoretical point of view. If anyone is able to explain it, I will be happy to find out. If not, the topic can be closed.

Kind regards,