 the gloves from blowing off. Likewise, if the pressure is too low, the controller fills 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 on the gauge indicate the current settings and the black one (coincident with the lower setting in this photo) indicates the current pressure.|
Having the glovebox at a negative pressure with respect to the atmosphere is a Bad Thing because 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 is a foot pedal that allows one to manually 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 the box 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 side increases it. No, you can't press both sides at once!
The gloves are obviously an important component of the glovebox. The gloves on a glovebox 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 with oversized gloves.
The biggest threat to the atmospheric integrity of the glovebox comes from pinholes and cuts 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 and replacement is required if there are more than three or four pinholes on either glove (depending on size).
On a research grade glovebox, the atmosphere is purified to less than 1 ppm H2O 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 to hydrogen gas and heating it. The adsorbed oxygen is converted into water and the water is easily removed in vacuo.
Storage vessels like these make bringing solvent into a glovebox easy.
If you use a rotary evaporator in your glovebox, be sure to use bump traps like these.
This page was last updated Monday, November 8, 2010.
This document and associated figures are copyright 1996-2014 by Rob Toreki. Send comments, kudos and suggestions to us via email.