Raymond D. Kimbrough, Jr.
Georgia Institute of Technology Atlanta 30332
Laboratory Operations in an Inert Atmosphere without a Dry Box
The most widely understood technique for handling substances which are sensitive to moisture or oxygen of the air is the use of a dry box. This expensive piece of equipment is usually not readily available. Alternative procedures have been developed; however, they require equipment not found in most laboratories, stockrooms, or chemical supply houses. The organic chemist is often not familiar with such procedures and hence does not appreciate the utility of the techniques. The result is that the organic chemist gets along as best be can, spraying nitrogen into the flask containing the sensitive material and jamming the stopper in quickly before too much air gets in. The following is a description of an apparatus, made from readily available materials, with which many of the organic laboratory procedures can be carried out in an inert atmosphere. Mention is made of several additional ways in which the apparatus can be employed t,o advantage in undergraduate laboratories. First, the inert gas, usually nitrogen or argon, is taken from the cylinder a t a few pounds pressure and led into the nitrogen delivery apparatus (see the figure) through a needle valve, a. The gas then bubbles through a small amount of low vapor pressure oil (silicone oil or pump oil) in a side arm test tube, b. This allows the rate of flow of the gas to be adjusted as desired. The 76-cm tube leading into a flask of mercury, c, allows a large evacuated system to be filled with nit,rogen without sucking air into the system. I t also serves to keep the pressure from exceeding the few centimeters of mercury in the flask and provides an escape valve for the nitrogen when the system is filled. The uit,rogcn is delivered through a rubber tube attached at d. Several such nitrogen delivery systems can he attached to the same nitrogen line by inserting a T-connection for each needle valve. A minimum of two is necessary for most of the techniques mentioned belo>{-. If each container to be used has at least two openings, nitrogen ran he passed in one while the other is used to add or remove material from the container. The stream of nitrogen flowing out the second opening keeps any air from getting in. When the system to be kept under nitrogen has but one opening, an adapter can be inserted, allowing nitrogen to be passed into the system through t,he stopcock and to stream out the opening through which the contents of the flask are accessible, e and f. The three-way stopcock allows air in the nitrogen line to he displaced before the stopcock into the flask is opened. Such an adapter with standard taper joints a t the top and bottom should be used with standard taper equipment. Operations in an inert atmosphere can then be carried out with any apparatus by the inser-
tion of this type of adapter at an appropriate point. Since there will be a slight positive pressure in the apparatus due to the head of mercury in the flask, c, the connections in the system, either stoppers or standard taper joints, must be secured with rubber bands or springs. The transfer of a liquid or solution stored under nitrogen to another flask is depicted in the figure. The flask to which the liquid will be transferred, U, is fitted with an adapter and is evacuated and filled with nitrogen several times. Air is kept out by passing nitrogen through the adapter as the stopper is removed. Nitrogen is also allowed to stream out the adapter of the container holding the liquid to be transferred, x. A glass tube with two right angle bends is fitted with a
Diagram of mpporotus to perform the functions of a dry box
rubber stopper that will slide on the glass tube and is introduced into e, and the stopper is inserted in position I. When the stream of nitrogen has displaced all the air from the glass tube, the other end is put into f. The glass tube is then slid down through the rubber stopper into x until the end is below the level of the liquid, position 11. As the pressure above the liquid increases to the head of mercury in flask c, the liquid is forced up the glass tube and into the receiving flask without ever coming in contact with the air. The following procedure can be used to trausfer specific volumes of material: A pipet, fitted with a balloon over the top and with a rubber stopper through which the pipet will slide, is filled with nitrogen through the bottom of the pipet and allowed to empty several times. After the last time it is filled, the top of the pipet is put into the adapter of the container through which nitrogen is streaming. When the balloon is empty, the stopper is inserted in the top of the adapter. As the pipet is slid down through the rubber stopper into the liquid, again the nitrogen pressure above the liquid forces the liquid up into the pipet. The top of the pipet can be closed through the balloon in the usual manner. Volume
44, Number 2, February 1967
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A container equipped with an adapter can he used for the storage of air- or moisture-sensitive materials or solvents to be used with such substances, particularly when the container must he opened frequently. Ex-
114
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Journal of Chemical Education
amples of substances encountered in elementary organic courses include acetyl chloride, phenylhydrazine, benzaldehyde, Grignard and organo-lithium reagents, and solvents such as Grignard ether.
