Equipment Technique And Reagents

Glassware. A typical set of glassware with standard taper ground joints like those shown in Figure 1.1 would be employed in an undergrad course. The joints permit you to assemble apparatus quickly and securely, but they must also be greased carefully (do not let the vaseline squeeze down into reaction vessel), and they are acceptable only with joints that have the same exact taper. Never use 24/40 joints with 19/22 or 14/20 or vice versa. Never use ground glass joints with formulas requiring diazomethane; clear sealjoints are available at a small extra charge. Never perform a reaction without greasing glass ground joints.

Rubber stoppers may be used if you cannot afford ground glass jointed glassware. Rubber stoppers may be used in conjunction with ground glass joints. Make sure your rubber stoppers fit properly and lightly grease inside and outside with vaseline. Bore holes in stoppers carefully and size them to fit apparatus snug.

Cork stoppers can react with or contaminate certain chemicals and should not be used.

Other glassware necessary are as follows:

Erlenmeyerflasks and beakers. These are fairly expensive and may be replaced with heat proof pitchers found on coffee makers. Corning and several other companies make many different types of heat proof glassware that can be picked up at yard sales dirt cheap and used effectively in the laboratory. Remember, even the best glass can be broken by a rapid change in temperature. Sep-aratory and addition (dropping) funnels are sometimes the same piece used in either role. In some reactions they are a must. They have a valve at one end and can be stoppered at the other end and the entire funnel, even the valve, is made of glass.

Filtration and pouring funnels. These should be glass or stainless steel unless working with very "mild" compounds, e.g., H20; then plastic and aluminum are acceptable. Buchner funnels and their substitute will be discussed under filtration in the methods chapter.

Graduated cylinders. These are necessary and inexpensive. You should have a small size for measuring small amounts accurately (25 ml) and a large size for measuring large quantities rapidly (250 ml).

Capillary tubes. These are made from glass pipets by heating a pipet or glass tubing and pulling them in two when the glass has reached a workable temperature. These items are inexpensive and practice makes perfect.

Thermometers. A high quality thermometer is only about $8. It is best to purchase two — one for high temps and the other for low temps. Make certain it is for measuring degrees in centigrade as this is what all formulas require, unless specified differently. Candy, meat and other types of thermometers will not fit your apparatus, are not accurate enough for most reactions and are unacceptable.

Stirring. Stirring is usually unnecessary in reactions that require boiling as the turbulence of boiling is sufficient. In other reactions a stirring device shown in Figure 1.1 cannot be beat. If the reaction can be carried out in a beaker, then an eggbeater can be used if set up exactly as shown on the work bench diagram. Variable speed eggbeater type mixers are powerful, fast, cheap, plentiful and with a little ingenuity can easily be adapted to any stirring device, but they must be housed in a vapor proof box and must be mounted securely. Low amperage, sparkless, stirring motors can be bought from an electrical repair shop dirt cheap. Maxe sure they are sparkless or mount them inside a vapor box, like the eggbeater. Every lab should have at least two mixing devices, in case one mixer Ibreaks or in case two different compounds need to be stirred at the same time. Low amperage motors should be available for those formulas that require long periods of stirring. Magnetic stirring devices can be bought or built, but I feel they are weak, troublesome, expensive and inferior to a good mechanical setup.

Heating. There are three different sources for heating and your lab should have all three.

Bunsen burners. These are of very limited use, as most reactions require flammable substances. Their purpose is mainly for gkss work, generating and super heating steam (see work bench diagram for safe usage).

Steam heat. It is very easy to produce and can be used safely for so many things: steam distillations, steam cleaning, creating a vacuum, etc. No lab should be without it. Make sure that steam does not get into anhydrous or dry reactions.

Electric heating elements. These should also be available in your lab. They are sometimes the only heating device capable of producing higher temperatures.

Heating mantles. These are state of the art devices and are worth the cost. Show the plans from the work bench diagrams to someone electrically inclined. A good electrician can make you one of these in a matter of minutes and he should have all the parts laying around his shop. He should charge just a fraction of the price of a heating mantle. (Note: Make sure he knows that the element he made will be exposed to flammable vapors.)

Heating plates. Even if you have a good heating mantle you should get a heating plate. These are made from electric fry pans if done as shown. If you are unsure of what wire to use, ask someone who knows. Fry pans are usually good for developing 400°F (205°C). This is sufficient for most distillations, refluxing, and drying.

three way adapter

Continue reading here: Jointware

Was this article helpful?

0 0