Mar., 1920
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
AN ELECTRICALLY HEATED BOMB FOR AMMONIA SYNTHESIS By R. 0. E. Davis and Harry Bryan BUREAUO F SOILS, DEPARTMENT OB AGRICULTURE, WASHINGTON, D. Received October 2, 1919
c.
I n carrying on work on t h e synthesis of ammonia one of t h e first things necessary was t o design a bomb 3Hz = t o contain t h e catalyst. As t h e reaction Nz 2NH3 requires a catalyst working a t high pressure a n d a fairly high temperature i t was necessary for t h e bomb t o meet some unusual conditions.
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FIG 1
FIG. 2
FIG I-ARRANGEMENT OF BOMBHEADWITH CATALYST TUBEATTACHED FIG SPLIT N U TFOR HOLDIKG CATALYST T U B EIN POSITION
T h e t y p e of bomb described below has been used b y us in t h e work done in cooperation with t h e Nitrate Division of t h e War Department on t h e synthesis of ammonia. Several different designs were tried a n d most of t h e essentials worked out by the authors, with some modifications made with t h e cooperation of the Nitrate Division of t h e Ordnance Department. C a p t . P. C. Landolt suggested a modification of t h e catalyst t u b e which resulted in t h e use of a flanged t o p , though t h e method of attaching and removing i t is original with us. The size used for experimental purposes will allow t h e use of I O O cc. of catalyst. The outer shell is made of Ni-Cr iron, regular gun steel forgings, obtained from t h e Washington Navy Yard. These are bored o u t t o give a wall 1.5 in. thick. T o t h e t o p of this shell screws a flange of t h e same material, a n d t o this flange is bolted t h e plate forming t h e head of t h e bomb. The inside dimensions of the bomb here shown are 4.2j in. in diameter X 1 5 in. long. Closure is effected by means of recessed rings in t h e end of the cylinder wall, a n d corresponding raised rings on t h e cap, using a thin copper gasket between t h e two. T h e head of t h e bomb carries t h e heater, catalyst t u b e , and inlet and outlet pipes. T h e heating is done internally by electricity. T h e sides of t h e bomb are protected b y a fused quartz or glass tube. Other types of insulation proved ineffective because of t h e J
Published by permission of Chief of Ordnance
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permeability t o hydrogen a n d t h e high heat conductivity of hydrogen. T h e heater devised after many trials is made up of t w o concentric alundum tubes of I a n d 2 in. internal diameter, wound in series with double strands of No. 14 nichrome wire. This will maintain a temperature within t h e catalyst of j j o o C. T h e gases flowing into t h e top of t h e bomb pass down t h e outside of both tubes and up through a steel t u b e which carries t h e catalyst and which slips inside of t h e smaller alundum tube. The gases pass over t h e catalyst, which occupies I O O cc. volume, a n d o u t a t the t o p of t h e chamber. A pyrometer well inserted through t h e outlet piece dips t o one-third t h e depth of t h e catalyst chamber, and is believed t o measure t h e average temperature of t h e catalyst. T h e arrangement of t h e head of t h e bomb and heater are shown in Fig. I . After the head has been once bolted on i t is n o t necessary t o again remove t h e bolts unless t h e heater becomes damaged in some way. The catalyst t u b e is made of thin steel with a flange a t t h e top. T h i s flange attaches t o a similar flange on the outlet piece by means of small steel I-pins with a copper washer between t h e two flanges. T h e tube is made gastight in t h e head by use of a copper washer a n d pressed down by means of a split n u t (Fig. 2). For filling, t h e n u t is removed a n d the outlet piece lified out. The catalyst tube comes with it. The inverted tube is filled from t h e bottom, a layer of steel wool placed on i t a n d nichrome gauze held in place by a steel ring closes the end. A stream of d r y gas is kept flowing through t h e bomb and t h e catalyst tube during all these operations. T h e method of introducing the electric current to the bomb is shown in Fig. 3. This lead is about 18 in. long and is made of cold rolled steel with l/z in. wall. The current is carried by t h e steel rod passing through t h e center b u t electrically insulated from t h e sides by means of glass. A gas-tight joint is made near t h e top. An enlargement on t h e central rod carries prc, EL^^^^^^ LEAD FOR a fiber washer on t h e under INTRODUCING CURRENT'TO HEATER THE side and a :fiber cap on the upper. The steel cap when screwed in place forces t h e washers against t h e steel faces on t h e rod which carry slight grooves a n d a gas-tight joint is effected. The leads are made of considerable length t o prevent their becoming too hot a t t h e upper end and burning the fiber washers, thereby causing t h e joints t o leak
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gas. The steel rods are 8/g in. and attached to them are the wires by which the heater is supported. The heater is practically indestructible, and as it operates in a reducing atmosphere the wires can carry a considerable overload, so long as the meiting point of the resistance wire is not reached. In Fig. I the leads are shown in the head of the bomb. Because of the difficulty of using a wrench on the split nut with leads in this position, on one bomb they were set a t an angle of 4j9 t o the top, and on another were placed in the sidcs of the bomb just below the flange. All three methods were used successfully, though the last is most convenient
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concave, thus the bottom is ring-shaped and furnishes a suitable surface npon which the apparatus may rest when not in use. Into the top part of the bulb two glass tubes are sealed, one serving as an inlet and the other as an outiet for a stream of cold water. The condenser is designcd t o rest upon a lipless beaker. Further support is furnished the condenser by attaching a wire t o the inlet and outlet tnhes and fastening it t o an iron rod clampcd t o a ring stand. Supported in this manner the bealicrs can he removed without distnrhing the condenser. Several condensers are usually arranged i o form a series (Fig. 2 ) .
A NEW TYPE OF CONDENSER FOR THE DETERMINATION OF CRUDE FIBER BV C. A. Clemens Received October 14, L9IV
Numerous modifications of the refiux condenser for the determination of crude fiber by the official method of the Association of Official Agricultural Chemists have been suggested. The latest and best of these is the one designed by Howell D. Spears.’ A condenser has been designed and used in the lahoratorv of the South Dakota Food and Drur DeFro. 2
This condenser has an increased surface for condensation and is constructed so that the vapors begin condensing sooner than in other forms of condensers suggested for this purpose. This reduces the loss by evaporation t o a minimum The form of the condenser is such that it also prevents foam rising t o the top of the beaker. The concave surface in the projected portion of the condenser causes the condensed liquid t o return by numerous routes; thus tending t o break up the foam more than if i t were returned a t only one point. If this is insufficient t o break up the foam it is immediately broken npon contact with the portion of the condenser t h a t extends downward into the beaker, consequently there is no possibility of foaming over. The condenser can he used with lipless beakers ranging in size from 5 0 0 cc. t o 1000 cc., either tall or wide form. Other advantages are its compactness, lightness, and the ease with which i t is set up and taken down. The advantages of using a beaker instead of a flask are obvious. Experience has shown that condensation is practically complete when using this apparatus. The following are some of the duplicate determinations made with this apparatus: Crude Fiber 1Pri re*,,>
The condenser (Fig. I ) consists of a glass bulb, one side of which is blown in such a manner as t o extend downward. The lower surface of this projection is I
Tnir J o u n ~ ~11. ,(1919). 140.
The above determinations were made by the double filtration method. White china silk was used for the acid filtration. The silk was cut into circular pieces with a diameter of about 1 z . j cm. These were
