One Response to What are some tips for Identifying an Unknown Solid in a Chemistry Lab Practical?

1. 

   Dr Dave P on February 24, 2009 at 5:51 am

   It would be nice to know if this was an inorganic or organic compound – but I’ll just assume it’s organic.

   1) Make sure all your glassware is clean

   2) Be careful handling the solid – you are only given on sample – divide it into two and place 1/2 in a separate labeled vial for your final tests. Use only a SMALL amount for each test you do, and don’t leave it laying around uncovered or stoppered.

   3) Check solubility first (these are all test tube tests)

   a) acid (could be an amine, or a aniline, or a amide)
   b) base (could be a carboxylic acid or a phenol)
   c) water (polar)
   d) toluene (nonpolar – possible aromatic ring)

   4) Take melting point (is it sharp? ==> if no ==>

   find a recrystallization solvent – a solvent that it will dissolve when hot, but solidify when cooled, this may take hours!

   try ethyl acetate
   ethyl acetate mixed with various % hexane (5,10, 15, 20 ,etc)
   alcohol
   methanol
   toluene
   isopropanol
   alcohol/%H2O (like hexanes above)

   6) Get good MP

   7) Take Infrared spectrum to get functional groups

   with a MP, IR, and functional groups you should be able to get a pretty good idea of what you compound is!!

   NOW
   All you have to do is make the derivates with sharp mp’s to prove it!