Presentation on theme: "Flash Evaporation to remove methylene chloride and The recovery of the Aniline from Extraction."— Presentation transcript:
Flash Evaporation to remove methylene chloride and The recovery of the Aniline from Extraction.
At this point, you should be able to account for the following items. If you have all three of the above items, FLASH EVAPORATION You are ready for the FLASH EVAPORATION. (p. 135-6 in Zubricks)
Start setting up with a good sturdy ring stand. If the rod is loose, tighten it before you begin so your set-up won’t WOBBLE
Place the burner on the stand. Be sure your burner has a needle valve to adjust gas flow, and a rotating barrel to control air- flow.
Now, add the iron ring Leave 2 to 3 inches for the flame.
The wire gauze is next. The wire gauze should have a ceramic center. Don’t worry if there is hole in it.
A beaker serves as a hot water bath. Select a large beaker with sufficient capacity for your 50 mL RB flask.
Clamp your 50 mL RB flask in the water bath Place the flask as far into the water as possible Place the flask as far into the water as possible.
Attach the three- way adapter atop the flask. (The adapter is commonly called the “still head”.)
CLAMP the condenser to another ring stand. Do NOT trust a rubber band to hold that $60.00+ piece of glassware !
Arrange an Erlen- meyer flask in an ice slurry for your receiver. You may want to clamp the receive onto another ring stand.
Attach water hoses to the condenser Water always enters from the LOWER end of the water jacket.
Place the sep funnel on top of the still head. No need for a stopper; but be sure the stopcock is CLOSED !
Remove the spent magnesium sulfate from the aniline- in- methylene chloride solution. Wash with small portions of methylene chloride; collecting all of the filtrate.
Make sure the stopcock is CLOSED. (Don’t be one of those who will forget!) THEN, transfer the filtrate into the sep funnel.
Now, light the burner and adjust to a good hot flame. Bring the water in the beaker to near boiling.
Then, adjust the burner to a smaller flame. The object is to keep the water bath hot.
Open the stopcock SLIGHTLY and allow slow steady drops to fall onto the hot flask. Methylene chloride (bp 40 o ) boils over (in a flash?) as the high boiling aniline (bp 185 o ) remains behind.
To save some time, while the Flash Evaporation is going on, you could filter the magnesium sulfate from your p-dichlorobenzene and evaporate off the methylene chloride. For this purpose, a number of small hot plates have been borrowed from the Frosh lab and are placed near your lab stations.
Some are small, 4 x 4 inch hot plates, and some are larger, and can accommodate several beakers.
Finally, only aniline remains in the RB flask. Discard the methylene chloride in the receptacle provided for it; -- and prepare to collect the aniline.
Collecting the Aniline by distillation through an AIR-COOLED condenser.
Turn off the burner flame. Remove the ice bath and receiver. Discard the methylene chloride in the receptacle provided Remove the ice bath and receiver. Discard the methylene chloride in the receptacle provided.
Drain the water from the water jacket. Remove the hoses from the condenser
Remove the sep funnel from the “still head”. Loosen the blue retainng nut and return the sep funnel to the box from which you got it.
You no longer need the water bath. Remove it and return the large beaker to the cabinet from which you got it Remove it and return the large beaker to the cabinet from which you got it.
Lower the RB flask to sit firmly on the wire gauze. LEAVE NO AIR SPACE! Lower the condenser assembly and re- attach it firmly to the still head. NO WATER HOSES!
Place the thermo- meter assembly into the still head. The thermo- meter bulb should be just below the side- arm of the still head.
Pre- weigh and label two DRY 50- mL Erlen- meyer flasks. The first is to catch the “forerun”; the second is to catch the final product (aniline).
With a good, hot flame, distill the contents in the RB flask. Switch receivers as the temper- ature climbs rapidly toward 180 degrees Switch receivers as the temper- ature climbs rapidly toward 180 degrees.
Collect the aniline that boils at 180- 185 degrees. Never distill to a dry flask. When dark droplets spatter and char in the RB flask, you will have difficulty cleaning it!
Part F- Part F- recovering the neutral compound Remove the spent MgSO 4 by gravity filtration.
UNDER THE HOOD, UNDER THE HOOD, evaporate to near- dryness on a hotplate. Cooling the residue should leave crude, solid p-dichlorobenzene.
Transfer the residue into a larger RB flask, and steam distill the mixture as before. Collect the distillate in an ice-cooled receiver. Recover the product on Buchner with suction.
THIS CONCLUDES THE EXPERIMENT ON EXTRACTIONS Keep the aniline. Complete your laboratory report form, and prepare to turn in your two solid products. Keep the aniline.