Guidelines for care & Use of Dry Solvent Stills [Example]

Use of Reflux Condensers
Both undergraduate organic laboratories and research laboratories frequently require the heating of
liquid mixtures to facilitate chemical reactions. These mixtures are composed of reactants dispersed in
organic solvents, usually in round-bottomed flasks capped by upright, jacketed water-filled glass tubes
refereed to as reflux condensers.
Common, generally nontoxic solvents can be refluxed on open laboratory benches. Ideally,
however, all reflux condensers should be set up in a hood, in case too much heat is applied and vapors rise
out of the condenser. Since boiling solvents do not increase in temperature, increasing the heat applied will
only cause loss of solvent vapor, not an increase in reaction rate. A condensation level of 1 or 2 inches
above the bottom of the condenser tube is all that is necessary.
Tap water is cold enough for most refluxes. However, very low boiling solvents like acetone or
ethyl ether may require ice-cooled water supplied with submersible lab pumps. Constant temperature waterbaths
can also be used.
The condensers should be placed vertically onto the round bottom heating flask and attached
firmly to ring stands with metal clamps. The water inlet should be through the lower end of the condenser.
Water hoses should be clamped onto water inlets/outlets on the condensers with Ace Glass wire hose
clamps (located in the stockroom for Departmental use) or thick copper wire, twisted on firmly with a pair
of pliers (Thin wire could eventually slice through the tubing). Hose clamps are not a good idea. Surging
pressure in Salem Hall water lines could cause water hoses to slip off if they are held onto a serrated
condenser hose adapter fittings with flat hose clamps. The only disadvantage of using wires is that you
must cut them off periodically when they become corroded and replace them. Use of Tygon tubing, instead
of rubber, will allow you to actually see the water flowing through the hose. You can then run water
through with a relatively slow speed, which is all you need in water condenser coils. Also, this means there
will be less chance of a spill when inevitable water pressure surges occur in Salem Hall at night. The water
pressure never falls to zero, so you basically can’t have the water flow on too low. Once you have
connected the water hose clamps, gently but firmly pull on the lines to make sure they are on tight.
I am currently looking for inexpensive in-line water flow indicators (will purchase those without
molded plastic halves which could pry apart under water pressure surges) which you can attach anywhere in
the water line to more readily judge the flow of water through the line.
You may also purchase Water-Flow Monitor sensor instruments with solenoid valve automatic
water shut-off mechanisms for about $600 from I2R Company.
"Bumping" of solvents can be avoided by adding boiling stones.
Magnetic stir bars can also be added to stir the boiling solution, allowing more even boiling.
Safe Use of Laboratory Centrifuges
Lab centrifuges in Salem Hall are of the low-speed type, and do not need special handling
requirements. They are supported on suction-cup feet and will not ordinarily wobble to the point of falling
off bench tops. Balance them by placing test tubes half filled with water immediately opposite the test tube
being centrifuged.
Occasionally check the power cord and keep extraneous lab equipment from cluttering bench tops
near the centrifuge.
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