0
$\begingroup$

I do have a cube of solid aluminum. But I need to verify that it is really Al to validate my research. What simple scientific techniques do you recommend?

$\endgroup$
  • 1
    $\begingroup$ Do you want to verify purity? Or the question is that if it is aluminum, and not eg iron? In the later case simple density measurement would show you a lot. $\endgroup$ – Greg Jun 10 '17 at 15:10
  • $\begingroup$ Would density measurement be valid/acceptable in research studies? I just want to clarify if a sample is mostly made up of Al. $\endgroup$ – Acid Jun 11 '17 at 11:38
  • $\begingroup$ Acceptable or not, it depends on the field, the accuracy you need, the probability of alternative materials, your exact question... Most studies already know what is their standard sample, or else they wouldn't use it. $\endgroup$ – Greg Jun 11 '17 at 23:01
2
$\begingroup$

If you want a simple one, then you might want to just perform qualitative analysis (QA) using aqueous sodium hydroxide and aqueous ammonia. Firstly, dissolve a portion of the cube using a small volume hydrochloric acid. Then, add a small volume of sodium hydroxide to a small volume the metal chloride solution. To another small volume of the metal chloride solution, add a small volume of aqueous ammonia.

For the first test, aluminium ions would first give a white precipitate but will dissolve in excess. For the second test, aluminium ions would first give a white precipitate but will not dissolve in excess.

Lastly to confirm, add aqueous potassium iodide to the sample. If no precipitation occurs, the sample is indeed aluminium chloride solution and the cube does indeed contain aluminium.

Alternatively, this paper here also provides some insights on verifying if something is indeed aluminium:

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/08/346/8346019.pdf

Unfortunately, the method I have mentioned and the methods in the paper are destructive as they require you to chip of a piece of metal from the cube for analysis. So... if you can't afford to do that then they cannot be used.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Can you give the source of your information in the method that involves sodium hydroxide and aqueous ammonia? $\endgroup$ – Acid Jun 19 '17 at 11:06
  • $\begingroup$ I learnt it in chemistry class. Online sources include: rsc.org/learn-chemistry/content/filerepository/CMP/00/000/534/… (Pg 207) chemistryforsg-olevel.blogspot.sg/2012/01/… $\endgroup$ – Tan Yong Boon Jun 19 '17 at 17:02
  • $\begingroup$ Although RSC claims that it is a "colourless precipitate", from my recollection during the lab sessions and the lab demonstrations I have watched online, it should be a white precipitate. $\endgroup$ – Tan Yong Boon Jun 19 '17 at 17:06
  • $\begingroup$ Are those 2 test methods that uses aqueous sodium hydroxide and aqueous ammonia different/separate from each other? $\endgroup$ – Acid Jun 25 '17 at 8:32
  • $\begingroup$ @J.C.Hernandez They are separate tests as in they are conducted separately. However, the results of the tests corroborate with each other to give you the conclusion (i.e. confirmation that it is aluminium). $\endgroup$ – Tan Yong Boon Jun 25 '17 at 8:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.