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scales from which the first two quantities were taken have different number densities. The scale with the larger number density will determine the direction in which the hairline should be moved to give the desired sum (or difference). After this
Vol. 4, No. 3
it takes three or four more guesses, and the solution is obtained with slide rule accuracy. RECEIVED March 28. 1932.
Improved Unit for Removal of Solid Particles from Gas Streams R. C. STRATTON, J. B. FICKLEN,AND EDW.W. KRANS Travelers Insurance Company and Travelers Indemnity Company, Hartford, Conn. Figures 2 and 3 show the unit which was used in this laboratory. The air to be sampled is drawn through tube A against the bottom of crucible E , where the air or gas streamis broken up and allowed to pass through the holes of the crucible into the washing solution in a series of small b u b b l e s , a f t e r s t r i k i n g against the bottom of bottle. As the bubbles rise through the solution their progress is somewhat retarded b e t w e e n the s i d e s of the Gooch crucible and the jar, thereby giving a slight scrubbing action. The effects just mentioned tend to give surprisingly good quantitative results in the removal of foreign materials from the gas stream. It was found that 150 ccm. of washing solution were s a t i s f a c t o r y for general p u r p o s e s w h en using this apparatus. The use of this unit is not conFIGURE 1. DIAGRAM OF APPARATUS fined to sampling air for metallic dust particles, but may be used for sam1 piece Pyrex glass tubing, 9 mm. outside diameter pling air for dust counting, the absorption of vapors, gases, 1 Pyrex hydrometer jar, 52 X 200 mm. inside dimension and many other applications. 1 Coors porcelain Gooch crucible No. 4, glazed 1 No. 7 rubber or cork stopper 1 No. 11 rubber or cork stopper
I
N A recent study of m e t a l l i c
fumes and p a r t i c l e s in air, it was n e c e s s a r y to use an apparatus for the a b s o r p t i o n of the particles in a suitable dissolving acid when the rate of flow of the air varied between 0.2 and 1.0 liter per minute. Several types of gas-washing units were tried, such as the ordinary type of gas-washing bottle, a bottle having a glass spiral, a porous, fritted plate bubbler, and a bottle provided with an impinger unit so arranged that the gas or air stream struck the bottom of the bottle a t a relatively high velocity. None of these absorption units proved entirely satisfactory. After c o n s i d e r a b l e experimentation the apparatus shown in F i g u r e s 1, 2, and 3 was developed and gave surprisingly efficient and uniform results. The material n e c e s s a r y for the construction of one absorption unit is as follows:
FIGURE 2. SET-UP OF APPARATUS
Referring to Figure 1, tube A should be inserted in s t o p p e r F so that the end of the tube is 10 mm. from the b o t t o m of Gooch crucible E and the crucible placed so that the bottom of the c r u c i b l e is 10 mm. from t h e bottom of the bottle. The assembly A should be so located as t o be in t h e c e n t e r of j a r D.
FIGURE 3. CRUCIBLEWITH TUBESIN PLACE
This unit should find favor with investigators because of its simplicity of construction, its low cost, and its high degree of efficiency. RECFJVEDFebruary 29, 1932.
