Brine electrolysis with alluminum

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The discussion centers on an electrolysis experiment using aluminum electrodes and NaCl as the electrolyte. After the process, a greasy precipitate, likely aluminum hydroxide (Al(OH)3), was observed. The precipitate's appearance may have been influenced by the carbon coating on aluminum foil electrodes. The remaining evaporated solution yielded crystals, which are suspected to be either NaCl or sodium aluminate. It is noted that sodium cannot form compounds with aluminum, as both are metals. The likelihood of the crystals being NaCl is high, especially if the solution did not turn yellow, which would indicate the presence of chlorine gas or sodium hypochlorite (NaClO). The discussion also warns against using NaCl as an electrolyte due to the potential release of chlorine gas, which is hazardous. Overall, the crystals are most likely NaCl, given the conditions described.
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I did an electrolysis with alluminum eletrodes, the electrolyte was NaCl, After completing it the left over was a gresyish precipitate (I assume aluminum hydroxide), I put most of it for evaporating in a cup, the rest evaporated leaving a jell, then later crystals. are the crystals NaCl which is covering the left over hydroxide or is it Sodium Alluminate.
 
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Firstly, sodium can not form a compound with aluminium. They are both metals, and except for rare cases, metals do not form compounds with each other.
Secondly, the percipitate is probably Al(OH)3 like you suspected. Generally, Al(OH)3 is a fine whitish percipitate. However, if your electrodes were aluminium foil, then the carbon coating could make the percipitate look grey,

Next, depending on how long the electrolysis ran, your crystals could be NaCl or NaClO, assuming you used an undivided cell. I highly doubt you ran it long enough for there to be any appreciable amount of NaClO in the solution, and you probably would have said that it smells like bleach. So, I am assuming the crystals are NaCl.

Generally, using NaCl as an electrolyte is not a good idea due to the evolution of chlorine gas, which is VERY dangerous. If you let it go long enough in an undivided cell with NaCl electrolyte, formation of NaClO (and Cl2 gas dissolving in the solution) will turn it yellow.
So, if your solution did not turn yellowish, your crystals are probably NaCl.
 
cpman said:
Firstly, sodium can not form a compound with aluminium. They are both metals, and except for rare cases, metals do not form compounds with each other.

Aluminates are quite common, http://en.wikipedia.org/wiki/Sodium_aluminate

In general, binary compounds (like caesium auride) are rare, but many metals are amphoteric and capable of producing salts - Al, Zn, Cr, Mn being the best known examples.
 
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