BauArf56 - 22-8-2019 at 03:02
Hi everyone!
I’m new in this forum, because i like much chemistry.
Some days ago, i did an experiment without knowing what i was doing. The experiment is the following:
I have prepared a solution of Calcium Hydroxide and i put a piece of aluminium in the solution. Some minute after, many bubbles of gas (should be
hydrogen) was exit of solution. After 5/10 minutes, the gas stop to exit and there’s a grey/black precipitate. Since i didn’t know what i do, i
threw all. After do this, i did some research, and i have supposed that the precipitate was Calcium Aluminate (CaAlO3). Is this quite right? Can
someone explain this reaction?
Anyone who can help me is welcome!
P.S. excuse the bad english, i’m from Italy
teodor - 22-8-2019 at 04:10
Welcome to the forum!
I've attached some paper which studied the reaction between aluminium and Ca(OH)2. You can get Al(OH)3 as well as some calcium aluminate or their
different combinations depending on the pH, see the paper. All are insoluble. I think the presence of calcium alluminates can lead to a cement-like
properties of the precipitate.
Also, if you use an aluminium foil typically it is not a pure aluminium, it contains mica-like component which covers the foil from one side, it forms
gray residue.
I did this experiment for beginners, just to understand better this chemistry: http://www.mesacc.edu/~paudy84101/CHM151LL/6B%20Alum.pdf . So, you can do it also and compare results with your experiment.
Attachment: kanehira2013.pdf (2.6MB)
This file has been downloaded 244 times
[Edited on 22-8-2019 by teodor]
[Edited on 22-8-2019 by teodor]
draculic acid69 - 23-8-2019 at 06:11
Concrete or cement is tricalciumaluminum silicate. Calcium aluminate would probably have some similar properties wouldn't it.