Flow Divider for Gases JOHAhNES H. BRUUh Sun Oil Conipany Experimental Division, Norwood, Penria.
I
N CHEMICAL and physical reactions involring gases or vapors of lowboiling compounds, i t is frequently rieces-
however, is noi,mally inserted in various positions, and by thus restricting the orifice of capillary A the amount of gas passing through it may be decreased within fairly wide limits (from about 50 to about 10 per cent of the total gas). If it is necessary to use a very small fraction (1 to 20 per cent) of the main gas stream for analytical purposes, should be used for the large side stream (80 to 99 per cent of total gas) and A for the small side stream (20 to 1 per cent of total gas); in this case B should be closed, unless an additional small side stream is desired. Sometimes one may wish to divide the main gas stream into four or more smaller side streams. In such cases the floiv divider shonx in Figure 1 should be modified by increasing the number of capillary outlets. The rubber stoppers may be eliminated by, fastening an iron rod to the upper end of the Tvires and by using a solenoid for lon-ering or raising the wire. CALIBRATIOS OF FLOW DIVIDER. The flow divider shown in Figure 1 was calibrated by passing various amounts of air through it with wire A inserted in different positions in the capillary while outlet 111 was closed and capillary B was open and unrestricted. The two side streams, d and B , were measured by passing the exit gases through gas meters. The calibration curves are shovin in Figure 2 for gas rates varying from about 1 to 5 liters per minute.
sary to divide the gas stream either before or after its passage through the reaction chamber into tn-o or more smaller streams containing definite proportions of the total gas.
k2 !
DIVIDERFOR GASES FIGCRE1. FLOW
LENGTH
30
2; /N MM OF
~
40
50
60
'
70
sb
CONSTR/CTED POR~/O/V of CAP~LLARY A
FIGURE2. CALIBRATION CURVES Sometimes i t may be desirable to distribute the main gas stream equally between t v o or more reaction chambers; a t other times one may n-ant to take out side streams containing, for instance, 10 per cent each of the original gas Ftreani or of the gaseous reaction product for analytical or other purposes. The general method used for dividing gas streams consists in placing the conventional T- or Y-tubes in the system and regulating the amount of gas passing through each side arm by means of either lubricated glabs stopcocks or adjustable clamps placed on the rubber tubing. Smce these methods leave considerable room for improvement from the standpoint of accuracy, as well as ease of manipulation, new methods were studied. These inrestigations h a r e led to the construction of a new flow divider which has been found T-ery satisfactory for laboratory purposes.
Wire, 1.7-mm. diameter Capillary, 2.2 X 80 mnl.
Some ieaderb may wonder why in the absence of the uire (at zero abscissa in Figure 2) the amount of gas passing through A is not exactly 50 per cent of the total of all a t the gas rates tried. The occurrence of three curves instead of one is due to the fact that it is very difficult to seal in two capillaries in exactly identical manner; consequently, a slight difference will be found betiyeen their resistances to gaseous flow, and this difference nil1 vary somewhat with the different gas rates and back prewires employed.
-4cknowledgment Tlie author wishes to acknowledge the assistance of Francis H. Murphy in the calibration of the flow divider, which is made by the Otto R. Griener Co., 55 Plane St., Sewark, N. J.
The flow divider is based upon the same principle ab the adjustable orifice flotymeter (I), in which the resistance of a capillary tube to gaseous flow is varied by inserting a wire of suitable size in the capillary. When the flow divider shown in Figure 1 is in normal use, the gas enters from the left. Wire B is normally kept in the position shown, leaving capillary B entirely open and unrestricted. The main side stream will consequently be discharged at B. Wire A ,
Literature Cited (1) Rruwi, J. H., IND.ENC.C H E ~ -4nal. ~ . , Ed., 11, ti55 (1939).
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