1. R. Ocone and Joseph Simkin
Pennsalt Chemicals Corporation Wyndmoor, Pennsylvania
1 I
An Efficient and hexpensive Inert Gas Chamber
Recently we have found it advantageous to use a modified plastic bag, shown in Figure 1, in place of a coi~vcntionaldry box for a number of operations. The chief advantage has been the increased speed with which an inert atmosphere can be established in a plastic bag of small dimensions. An added advantage is the low cost of construction. When badly fouled with accidental spills of working materials, the bag may be discarded since a new one may be manufact,ured quickly and simply. To make such a bag two sheets of light gauge (I1/%mil) polyethylene are laid over a pattern drawn on heavy kraft paper, and a heated sealing wheel' is used to seal together the two polyethylene sheets along the single heavy line drawn in Figure 2. Other heat-sealable films may also be used but we chose polyethylene because it is an excellent moist,ure barrier. The excess polyethylene is trimmed off, and the bag is turned inside out so that the gloves extend into the bag. After one
' Model 50, Sealine Manufacturing Corp., 4716 West Lake St., Chicago 44, Illinois.
Figure 1.
"Dry bag" in use.
Figure 2.
Pattern for "dry bag."
becomes experienced in the use of the sealing wheel, a "dry bag" may be manufact,ured in about 15 minutes. We have found that a hag 22 in. wide and 24 in. long (wit,h the flap folded) is a convenient size for carrying out most operations. However, these dimensions are not critical, and we have put together bags of other dimensions to accommodate special operations. In use, a nitrogen inlet t,ube is inserted into the narrow opening at the top of the bag and secured by wrapping with a rubber band. The. nitrogen flow is started with the entry flap open and the "dry bag" flat on the table. Because of the small volume of the bag u w have found that 10-15 minutes of purging with a moderate gas flow is sufficient to establish a good inert atmosphere. Transfer of materials can be made at any time while the hag is in use by merely sliding the materials through the flap while there is a st,rong gas flow. When the operator is assured that the purging is complete, he folds the flap and clips it loosely. At this point the bag starts to inflate and the gas flow may be adjusted to a level sufficient to maintain only a slight flow through the folded flap. The operator then inserts his hands in the gloves and carries out the required manipulations 2s shown in Figure 1. Thr bag is transparent so that all materials in the bag ar? completely visible. It is obvious from this description that some operations such as those involving very bulky apparatus can be done more convenient~ly in a conventional dry box. However, we have found that a number of laboratory operations requiring inert atmospheres are most conveniently carried out in the "dry bag" described above. I t has also been possible to store sensitive materials in the "dry bag" by tightly closing the openings when operations had to be interrupted or postpmed.We are indebted to the Office of Kaval Research for partial support of our work.
Volume 39, Number 9, September 1962
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463
