Glove Boxes

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Glove Boxes

Key features of a glovebox

The Antechamber

A glovebox is not much good if you don't have

a way of getting your materials in and out. If

you look at the pictures above, you'll noticethat there is a sealed chamber on the right side

of the glovebox. This chamber is called the

antechamber (or "port" by some) and it has

two doors -- one that can be opened only from

the inside of the box and one that can beopened only from the outside. As you can see

in the photo on the left, the outer door to theantechamber is open, ready for glassware to be

placed inside. See below to see how the

antechamber is used.

The antechamber can be evacuated with a pump or filled with nitrogen gas. Never have

both doors open at the same time!!

The Photohelic Gauge

The photohelic gauge controls the

upper and lower pressure limits in aglovebox. Modern gloveboxes use a

solid state controller or touch screen

interface, but the function is thesame. If the pressure in the box gets

too high, the controller

automatically opens a valve to the

vacuum pump to relieve the excesspressure and prevent the gloves

from blowing off. Likewise, if thepressure is too low, the controllerfills the box with nitrogen. You can

set these upper and lower limits by

turning the two small knobs below

the gauge. The two red needles onthe gauge indicate the current


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settings and the black one

(coincident with the lower setting inthis photo) indicates the current

pressure.

Having the glovebox at a negative pressure with respect to the atmosphere is a Bad Thingbecause air will be drawn into the box through any small pinholes or leaks. Therefore,

one tends to operate a glovebox at a slight positive pressure (i.e. both the cutoffs should

be to the left side of zero).

The Pedatrol

The pedatrol is a foot pedal that allows one tomanually adjust the pressure inside the glovebox.

The high and low limits set on the photohelic gauge

still apply, but you can use the pedatrol to open thebox to the vacuum pump or the nitrogen supply to

get the pressure to a comfortable working level.

Notice that the pedatrol is sort of like a two-button

computer mouse. Pressing on the left side decreases

the pressure in the box and pressing on the right sideincreases it. No, you can't press both sides at once!

The Gloves

The gloves are obviously an important component of the glovebox. The gloves on aglovebox are usually sized large so that anyone can get their hands in. This makes life a

bit difficult for people with small hands, but one quickly learns how to deal withoversized gloves.

The biggest threat to the atmospheric integrity of the glovebox comes from pinholes andcuts in the gloves. The most common ways of damaging the gloves involve the use of

razor blades, copper wire (sharp ends), syringe needles and scissors inside the box. If you

do use any of these BE EXTREMELY CAREFUL!! Gloves are rather expensive andreplacement is required if there are more than three or four pinholes on either glove

(depending on size).

The Drytrain

On a research grade glovebox, the atmosphere is purified to less than 1ppmH2O and less

than 5 ppm O2 by circulating it through a catalyst bed (also called a "dry train"). The

catalyst bed contains Q5 catalyst to remove oxygen as well as zeolites to remove water.After a period of use, the dry train is regenerated by isolating it from the box, exposing it
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to hydrogen gas and heating it. The adsorbed oxygen is converted into water and the

water is easily removed in vacuo.

Schlenk Lines and Vacuum Lines

One or two manifolds?

A Schlenk or high vacuum line consists of a glass manifold that has severalstopcocks, valves or

openings in addition to a connection to a vacuum source (typically a mechanical and/or diffusion

pump). Having several ports on the line is convenient because several different flasks or reaction

vessels may be used simultaneously. For example, gases can be vacuum transferred from one

flask to another or several reactions may be run at the same time.

These lines may be of a dual or single manifold design. In a single manifold design, the

manifold's main purpose is for vacuum. Here is an example of a single manifold design

which uses all-Teflon(tm) valves and O-ring joints to ensure a good vacuum seal. Eachport has its own independentbubbler, so up to three reactions can be stirring under

nitrogen at one time.

A dual manifold design provides one manifold for vacuum and another for nitrogen or a

reactant gas. A connection between the two manifolds permits the nitrogen manifold to

be easily evacuated.

Shown below is a diagram of a dual manifold high vacuum line. Note that the lower

manifold is for vacuum and the upper one is for nitrogen.
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Two features worth noting in this drawing are:

1. Main Trap. When the line is running, this trap is immersed in a liquid nitrogen dewar.This stopsvolatileorcorrosivevapors that have escaped the pre-trap and prevents

them from entering the pump. New pumps can cost one to two thousand dollars, so

protecting the pump is its ONLY role. NEVER PULL SOLVENTS INTO THE MAIN TRAP!

2. Pre-Trap. This is an additional liquid nitrogen trap to condense vapors or gases from thevacuum line. It is also used to collectsolventsthat are removed from reaction flasks. If

you are removing a lot of solvent from a reaction the nitrogen level will drop quickly, so

be sure to keep an eye on it.

Click on any of these manifolds for more information or to order:

Dual Manifold LineSingle Manifold Line Dual Manifold,

Souza Design
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Single Bank ManifoldDouble Bank Manifold

4-port Vacuum/Inert Line
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Glove Boxes