Author Topic: mystery compound sherlock pls  (Read 1214 times)

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fructose

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mystery compound sherlock pls
« on: October 10, 2001, 03:02:00 AM »
attempting to prepare some alcl3 i thought, 'oh, i'll just dissolve some al in hcl and the alcl3 will be right there for tha evappin' so, sheet after sheet of shiny foil bubbled and blackened it's way into the brew, but something was amiss. after inhaling way too much hydrogen that seemed to burn like it had never done before, i went to THE BOOK and was humbled. alcl3 reacts violently with water to produce hcl. further reading lead me to believe the al would now be floating around the clear solution as [Al(H2O)6]3+, which equilibrilises to [Al(H2O)6]3+ <=> 3H+ + Al(H2O)3(OH)3(s)...being in the mood for something concrete to salvage (even if it wasn't my beloved alcl3) i said, heck i might just precipitate the darn thing and be done with it. add a weak base, methinks, so i start bubbling CO2 through the crystal clear solution. after about 6 moles of CO2 my solution is still precipitatless, but my hand is burning where i was holding the tube in. my co2 pump was just some bicarb(aq) splashed with a little conc. H2SO4...oh no...could some SO2 have evolved, evapped, along with it? what WAS the mystery acid? i didn't care until i dried the shit out, but more on that in a second.

so i thought fuck it, i'll just add Na+ ions, and neutralised the al solutions with a few BIG pinches of bicarb. a cruddy white precipitate was suspended around and i thought great it's my Al(H2O)3(OH)3. so i boiled the stuff down with stirring (as there was insufficient crud to filter) came back to find my stir bar poised in green goo.
green? okay. washed twice with acetone which carried the green-yellow goo away leaving white gelatinous sand like crystals. spread them out to dry. although the co-ordinated waters weren't going to leave so the stuff would stay wettish, that i expected. what i didn't expect was that on exposure to air the shit goes yellow. all of it. bright flourescent sumblimed sulfur yellow!!! wtf? there's no free sulfur there cause it dissolved clear. acetones *cleans* it but then it returns. what al compound is yellow?!!?!

any ideas?

Rhodium

  • Guest
Re: mystery compound sherlock pls
« Reply #1 on: October 10, 2001, 03:06:00 AM »
What quality of Al did you use? There are probably some other trace metals present in it if you aren't using ACS grade Al. Those metals can probably produce the colors you are talking about.

fructose

  • Guest
Re: mystery compound sherlock pls
« Reply #2 on: October 10, 2001, 04:30:00 AM »
Al foil. Supermarket reagant grade. Are these trace metals simply floating around in the Al lattice?
How could they be present in such concentrations to prdouce a uniform flouescent yellow?


lugh

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Aluminum Chloride Synthesis
« Reply #3 on: October 10, 2001, 08:21:00 AM »
From Ber. 25, 3521 (1892) and JCS 1914 (1952):
One end of a large diameter Vycor tube (25 to 40 mm) is inserted through one of two holes in a cork closing a wide-neck flask. The second hole holds a tube leading to the hood. The cork can dispensed with if the reaction tube can be made to fit tightly into the neck of a long-neck, round bottom flask. The reaction tube is placed in an electric furnace. The distance between the hot zone and the receiver flask should not be longer than 8 cm, to prevent plugging of the tube by the sublimate. The cork is protected from the heat by an asbestos wrapping. A porcelain boat containing aluminum turnings or powder is inserted into the reaction tube. Gaseous HCl is then passed through the end opposite the receiver. The rubber tubing connections should be as short as possible. When the air has been completely displaced by the HCl, the furnace is slowly heated until a white mist begins to appear. The flow of HCl is then increased and the temperature raised to prevent premature condensation of the sublimate. The reaction is then allowed to continue until the aluminum has been completely consumed.

If one is interested in Aluminum Choride Hydrate one shouldĀ  consult Zeit. Anorg. Allg. Chem. for further information:

At 0 degrees C, aluminum chloride hydrate is slightly soluble (21mg/100ml) in saturated aqueous HCl and is therefore easily isolated from such a solution. The aluminum is dissolved in concentrated HCl and the solution is transferred into a three neck flask fitted with a stirrer, an inlet tube for HCl gas and an outlet tube. The flask is cooled to 0 degrees C and HCl is introduced into the continuously stirred and cooled solution until it is saturated. The inlet tube should not dip into the solution, since it might become clogged with salt, but sufficient adsorption of the HCl is ensured by vigorous stirring. A wash bottle filled with concentrated sulfuric acid connected to the outlet of the flask serves to indicate the progress of the saturation. The precipitated hydrate is rapidly suction filteredand, while cold, washed with some ether and dried on a clay plate.  :)  :)  :)

fructose

  • Guest
Re: Aluminum Chloride Synthesis
« Reply #4 on: October 10, 2001, 08:00:00 PM »
l-u-g-h luuuuugh!

thankyou!