WHY SODIUM FUSIONS?WHY SODIUM FUSIONS?Organic compounds usually contain carbon, hydrogen, and oxygen. Other element that may be present are: nitrogen, sulfur, and

halogens.These latter three elements are usually bound covalently, and are NOT water soluble. The

detection of these depends on converting them into water-soluble ions: CN-, S2-, and X-.

This is usually done by a “sodium fusion”.Sodium reacts violently with water. Extreme Sodium reacts violently with water. Extreme

caution must be exercised.caution must be exercised.

You need a 50 mL beaker half full with distilled water, a Bunsen You need a 50 mL beaker half full with distilled water, a Bunsen burner, a sample ground to a very fine powder, and a cleanburner, a sample ground to a very fine powder, and a clean

DRYDRY 3-inch test tube held in a test tube holder 3-inch test tube held in a test tube holder..

Be sure the beaker of water is placed Be sure the beaker of water is placed under your snorkelunder your snorkel..

With a paper towel, blot dry a small piece of With a paper towel, blot dry a small piece of sodium and place it into the test tube.sodium and place it into the test tube.

Over a low flame, heat the sodium until it melts into a shiny, silvery ball Over a low flame, heat the sodium until it melts into a shiny, silvery ball and vapors start to rise in the test tube.and vapors start to rise in the test tube.

Remove the tube from the flameRemove the tube from the flame and add a bit of the and add a bit of the powdered sample. There may be a bit of a reaction when you powdered sample. There may be a bit of a reaction when you

do this . . .do this . . .

You may You may re-heatre-heat, and add more sample if you wish, and add more sample if you wish..

Finally, re-heat the tube to a Finally, re-heat the tube to a dull reddull red

Move the tube from side to side to avoid Move the tube from side to side to avoid burning out the bottom of the tubeburning out the bottom of the tube..

When the tube is When the tube is RED HOT,RED HOT, PLACE PLACE (do not DROP)(do not DROP) the tube into the beaker of waterthe tube into the beaker of water. . Be sure the tube is Be sure the tube is not pointed at you, nor at anyone else at this time.not pointed at you, nor at anyone else at this time.

The tube should The tube should SHATTER!SHATTER! Expect a rather Expect a rather vigorous reaction, -- perhaps with fire and smokevigorous reaction, -- perhaps with fire and smoke ..

Heat the solution to boiling for a few minutes Heat the solution to boiling for a few minutes (Fig. 1). Then, gravity filter (Fig. 2) to remove broken (Fig. 1). Then, gravity filter (Fig. 2) to remove broken

glass and solid residue.glass and solid residue.

The clear filtrate is used to test for sulfur, nitrogen, The clear filtrate is used to test for sulfur, nitrogen, and halogens.and halogens.

Some may prefer to use hot platesSome may prefer to use hot plates

Conduct the tests on the Conduct the tests on the “KNOWN”, “KNOWN”, for sulfur, for sulfur, nitrogen, and halogens, as directed (nitrogen, and halogens, as directed (p. 45p. 45) in your ) in your

lab manual.lab manual.

When your Lab Instructor approves your tests, conduct the When your Lab Instructor approves your tests, conduct the sodium fusion tests on the sodium fusion tests on the “UNKNOWNS” “UNKNOWNS” which are which are

provided.provided.

Your Laboratory Report Form is due the day on which you Your Laboratory Report Form is due the day on which you perform the Sodium Fusions. Be prepared to turn it in.perform the Sodium Fusions. Be prepared to turn it in.

nafus-lr.doc LABORATORY REPORT SODIUM FUSIONS

NAME: ______________________________________Section:_________Date:_______________ NAME(S) of you Lab Partner(s):______________________________________________________

Results of Sodium Fusion Tests: Indicate with "+" where positive; but leave blank where negative.

Sulfur Nitrogen Halogen

Known

Unk ( )

Unk ( )

Unk ( )

1. Write the EQUATION for the formation of the black ppt that confirms the presence of sulfur. 2. Write the FORMULA for the blue ppt (Prussian Blue) that confirms the presence of nitrogen. 3. Write the EQUATION for the formation of the white ppt that confirms the presence of chloride ions. 4. What results would you expect in the test for halogens, if: a. sulfur is present, and the acidified filtrate is NOT boiled long enough to expel H2S? (Consider the appearance of: Ag+ + S2-

???) b. nitrogen is present, and the acidified filtrate is not boiled long enough to expel HCN? (Consider the appearance of: Ag+ + CN - ???) c. the filtrate was mistakenly acidified wiith H2SO4 instead of with HNO3? (Consider the appearance of: 2Ag+ + SO4

2 -- ???) d. the filtrate was mistakenly acidified with HCl instead of with HNO3?