Paul Z. Anthony Boxter Loborotories, Inc. Morton Grove, Illinois
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A Simplified Apparatus for Pressure Reactions
The conventional Carius combustion tube, used for performing small scale organic reactions under pressure in the laboratory, has been modified in order to make it more adaptable for routine use. For most laboratory workers it is difficult to produce a proper heat seal of the Carius tube; tubes often burst below rated pressure because of residual strains in the glass seal. Gordon' described an improved type of combustion tube made by sealing a smaller diameter tube on the heavy-walled tube; in this way all the seals except the small final seal can be oven-annealed at the factory. The disadvantages of the latter tube are: (I) the greater difficulty in filling, especially if any solids are involved, and (2) the still present problem of properly sealing the smaller opening. The modification described in this paper contributes to easier operation and greater economy over previously described equipment. No glass blowing experience is necessary and the same tube can be used repeatedly. The assembled combustion tube consists of an 18-in. length of flanged Pyrex pipe2 of l/zin. i.d. permanently sealed a t one end and capped a t the other end with a suitable gasket, aluminum disc, and aluminum screw cap3 as shown in the accompanyiilg illustration. The total volume of the pressure tube is 53 rnl, thus permitting reactions of a total volume of about 35 ml to be performed. A Teflon gasket can be conveniently made and is suitable for most types of reactions. Other gasket materials may be employed. The pressure vessel can be heated, if desired, by placing it in an appropriate length of 2-in. steel pipe sealed at both ends by steel screw caps and placing the complete unit in an oven a t any desired temperature. Because of it,s construction the modified pressure tube GORDON, C. L., J. Research Notl. Bur. Standards, 30, 107 (1943). Manufactured by Fiseher and Porter Company, Hatboro, Pennsylvania. "crew cap assembly available from Fischer and Porter Campany as standard equipment.
is a substantial improvement over the conventional type. It affords a superior type of seal with greater strength a t the point of closure than at any other part of the tube. This is in direct contrast to the ordinary type of Carius combustion tube which is weakest a t its seal point. Accordmg to Gordon1 the conventional Carius combustion tube will stand pressures up t o 1500 lb per sq in. at temperatures up to 300" whereas his modified tube will stand pressures of more than 2500 lb per sq in. The reusable pressure tube described in this article can be expected to be as resistant to reaction pressures as Gordon's tube. Reactions which have been run successfully in this apparatus are the following: (1) Inversion of ,sucrose a t 149°C in dilute HCI. (2) Preparation of 5-hydroxymethylfurfural from sucrose and oxalic acid a t 162°C in aqueous solution. (3) Preparation of diethyl aspartate and 2,5-diketopiperazinediacetamide from diethyl maleate and alcoholic ammonia a t 105'C. These are only a few examples of the flexibility of this reactor for conveniently carrying out small-scale pressure reactions. If a larger volume is desired, a tube of longer length and/or larger diameter can be used. Tubes made of Pyroceram, a new Corning glass product reportedly harder than steel and light as aluminum, should extend the scope of this technique. Larger scale pressure reactions will be possible because of the greater wall strength of this material.
Modiflcd Corius combustion tube. 11) Alumiuum disc, (2) asbestos gasket, 13) Teflon gasket, 14) aluminum screw cap, 15) mluminum ring, ( 6 )flanged ' / h . id Pyrex pipe.
Volume
36, Number 10, October 1959
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489
