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Flash Evaporation to Flash Evaporation to remove methylene chloride remove methylene chloride
andand
The recovery of the The recovery of the Aniline from Extraction.Aniline from Extraction.
At this point, you should be able to At this point, you should be able to account for the following items.account for the following items.
If you have all three of these, you are ready for Flash If you have all three of these, you are ready for Flash Evaporation; p. 135 ZubrickEvaporation; p. 135 Zubrick.
(Note: IF the methylene chloride had evaporated, (Note: IF the methylene chloride had evaporated, you will need to add more.)you will need to add more.)
You have gone to a great deal You have gone to a great deal of effort to of effort to DRYDRY everything everything.
• Then, from this point, be sure Then, from this point, be sure that that ALLALL of the of the glasswareglassware you use is you use is ABSOLUTELYABSOLUTELY DRYDRY..
Start Start setting setting up with up with a good a good sturdy sturdy
ring ring stand.stand.
If the rod is If the rod is loose, loose,
tighten ittighten it before you before you begin so begin so
your set-up your set-up won’t won’t
WOBBLEWOBBLE
Place the Place the burnerburneron the on the
stand. stand. The The hotplate is hotplate is
NOTNOT a a good good
option for option for this this
procedure.procedure.
Be sure your Be sure your burner has a burner has a needle valveneedle valve to adjust gas to adjust gas flow, and a flow, and a
rotating rotating barrelbarrel to to
control air-control air-flow.flow.
Now, Now, add the add the
iron iron ringring
Leave 2 Leave 2 to 3 to 3
inches inches for the for the flameflame..
The The wire wire
gauzegauzeis is
next.next.
The wire The wire gauze gauze should should have a have a
ceramic ceramic center. center. Don’t Don’t
worry if worry if there is there is
hole in it.hole in it.
A A beaker beaker serves serves
as a as a hot hot
water water bath.bath.
Select a Select a LARGELARGEbeakerbeaker
with with sufficient sufficient capacity capacity
for your for your
50 mL RB 50 mL RB flask.flask.
Clamp Clamp your your 50 50 mL RB mL RB flaskflask(NO (NO
LARGER)LARGER) in the in the water water bathbath
Place Place the flask the flask
as far as far into the into the water as water as possiblepossible
.
Attach Attach thethe
three-three-way way
adapteradapter atop atop the the
flaskflask.
(The (The adapter is adapter is commonly commonly called the called the
“still “still head”.)head”.)
CLAMPCLAMP the the
condenser condenser to anotherto another
ring ring stand.stand.Rubber Rubber
bands are bands are available to available to snug up the snug up the
condensercondenser..
But do But do NOT trust NOT trust a rubber a rubber
band band alone, to alone, to hold that hold that $50.00$50.00 piece of piece of
glasswareglassware!!
Arrange Arrange an an Erlen-Erlen-
meyermeyer flask in flask in an ice an ice
slurry for slurry for your your
receiver.receiver.
You may You may want to want to clamp clamp
the the receiver receiver
onto onto another another
ring ring stand.stand.
Attach Attach water water
hoses to hoses to the water the water jacket of jacket of
the the condensercondenser
Water Water alwaysalways
enters enters at the at the
LOWERLOWER end of end of
the the water water jacket.jacket.
Place Place the the sep sep
funnel funnel on top on top of the of the still still
head.head.
No need No need for a for a
stopper; stopper; but be but be
sure the sure the stopcock stopcock
isis CLOSEDCLOSED
!!
Remove the Remove the spent spent
magnesium magnesium sulfate sulfate (GRAVITY (GRAVITY FILTER)FILTER)
from the from the aniline – in - aniline – in - methylenemethylene chloridechloride solution.solution.
Wash with Wash with small small
portions of portions of methylene methylene chloride; chloride;
collecting all collecting all of the filtrate.of the filtrate.
Make Make sure the sure the
stopcock stopcock is is
CLOSEDCLOSED..(Don’t be (Don’t be
one of one of those those
who will who will forget!)forget!)
THEN,THEN, transfer transfer
the the filtrate filtrate
into the into the sep sep
funnel.funnel.
Light Light the the
burner burner and and
adjust adjust to a to a
good good hot hot
flame.flame.
Bring Bring the the
water in water in the the
beaker beaker to near to near boiling.boiling.
Adjust Adjust the the
burner burner to a to a
smallsmall flame.flame.
The The object object is to is to keep keep the the
water water bath bath hothot..
Open the Open the stopcock stopcock SLIGHTLYSLIGHTLY and allow and allow
slow slow steady steady
dropsdrops to to fall onto fall onto the the hot hot flask.flask.
Methylene Methylene chloride chloride
boils over boils over in an in an
instant instant
(in a (in a
flash?)flash?) as the as the high high
boiling boiling aniline aniline
remains remains behind.behind.
While the Flash Evaporation is going on, While the Flash Evaporation is going on, filter the magnesium sulfate from your filter the magnesium sulfate from your p-dichlorobenzene. Place the filtrate on p-dichlorobenzene. Place the filtrate on your hot plate your hot plate UNDER YOUR SNORKEL, UNDER YOUR SNORKEL,
and and evaporate off the methylene and and evaporate off the methylene chloride.chloride.
When the volume reached only a few mLs, When the volume reached only a few mLs, you may begin to see white vapors rising you may begin to see white vapors rising from the beaker. STOP the evaporating, from the beaker. STOP the evaporating, and COOL the contents. The residual and COOL the contents. The residual
p-dichlorobenzene “should” solidify.p-dichlorobenzene “should” solidify.
Finally, Finally, only only
aniline aniline remains remains
in the in the RB RB
flask.flask.
Discard Discard the the
methylene methylene chloride in chloride in the waste the waste receptacle receptacle provided provided for it; -- for it; --
andand prepare to prepare to collect the collect the
aniline.aniline.
Collecting the AnilineCollecting the Aniline
by distillation through by distillation through anan AIR-COOLEDAIR-COOLED
condenser.condenser.
Turn Turn off the off the burner burner flame.flame.
Remove Remove the ice the ice
bath and bath and receiver. receiver. Discard Discard
the the methylene methylene chloride in chloride in
the the receptacle receptacle providedprovided.
Drain Drain the the
water water from from the the
water water jacketjacket..
Remove Remove the hosesthe hoses from the from the condensercondenser
Remove Remove the sep the sep funnelfunnel from from the the
“still “still head”.head”.
Loosen Loosen the blue the blue retainng retainng nut and nut and
return the return the sep funnel sep funnel to the box to the box
from from which you which you
got it.got it.
You You no no
longer longer need need the the
water water bath.bath.
Remove Remove it and it and return return
the large the large beaker to beaker to
the the cabinet cabinet
from from which which
you got you got itit.
Lower the Lower the RB flask RB flask
to sit to sit firmly on firmly on the wire the wire gauze.gauze.
LEAVE LEAVE NO AIR NO AIR SPACE!SPACE!
Lower the Lower the condenser condenser assembly assembly and re-and re-attach it attach it firmly to firmly to the still the still head.head.
NO NO WATER WATER HOSES!HOSES!
Place the Place the thermo-thermo-meter meter
assembly assembly into the into the
still still head.head.
The The thermo-thermo-meter meter bulb bulb
should should be just be just below below
the the side- side-
arm of arm of the still the still head.head.
Pre-Pre-weigh weigh
and label and label twotwo
DRYDRY 50- 50-mL mL
Erlen-Erlen-meyer meyer flasks.flasks.
The first The first is to catch is to catch
the the “forerun”“forerun”
; the ; the second is second is to catch to catch the final the final product product (aniline).(aniline).
With a With a good, hot good, hot
flame,flame, distill the distill the contents contents
in the in the RB flask.RB flask.
Switch Switch receivers receivers
as the as the temper-temper-
ature ature climbs climbs rapidly rapidly toward toward
180 180 degreesdegrees.
Collect Collect the the
aniline aniline that that
boils at boils at 180- 180- 185185
degrees.degrees.
Never Never distill to a distill to a dry flask.dry flask.
When dark When dark droplets droplets
spatter in spatter in the RB the RB
flask, you flask, you may have may have difficulty difficulty
cleaning it!cleaning it!
Part FPart F-- recovering the neutral compoundneutral compound
Remove the spent MgSORemove the spent MgSO44 by gravity filtration. by gravity filtration.
(You may have done this while working with the aniline.)(You may have done this while working with the aniline.)
UNDER YOUR SNORKEL,UNDER YOUR SNORKEL, evaporate evaporate to near-dryness on a hotplate.to near-dryness on a hotplate.(You may have already done this too.)(You may have already done this too.)
Transfer the residue into a larger RB flask, and steam distillsteam distill the mixture as before.
Collect the distillate in an ice-cooled receiver.Collect the distillate in an ice-cooled receiver.
Recover the product on Buchner with suction.Recover the product on Buchner with suction.
THIS CONCLUDES THE THIS CONCLUDES THE EXPERIMENT ON EXTRACTIONSEXPERIMENT ON EXTRACTIONS
Complete your laboratory report form, and Complete your laboratory report form, and prepare to turn in some of your productsprepare to turn in some of your products.