Calibration of Glass-Wool Flowmeters. Joseph Grumer, Harold Schultq and Magaret E. Harris, Explosives and Physical Sciences Division, Bureau of Mines, Pittsburgh, Pa. URING
method may be used to extend a single linear flowmeter calibration on one gas to other mixtures where an accuracy of no better than several per cent is required and the downstream absolute pressure and temperature are sensibly the same. The two flowmeters were calibrated with each mixture within + I % of the instantaneous flow.
the war, the National Bureau of Standards ($2, 3 ) de-
D veloped a linear-resistance flowmeter, using a glass-wool porous plug as the resistance element. Data reported below show
LITERATURE CITED
that a single calibration of such a flowmeter can be extended to other gases by theoretical considerations. The approximate equation of flow ( 2 ) through a porous plug in the range between molecular slip flow and turbulent flow in the plug is given by Equation 1 : K AP (1)
(1) Bromley, L. A., and Wilke, C. R , Ind. Eng. Chem., 43, 1641 (1951 ). (2) Iberall, A. S., Natl. Bur. Standards J . Research, 45, 398 (1950). (3) National Bureau of Standards, Rept. 6.2/6211-2885 (Sept. 25, 1947).
v=-
supported in part b y the American Gas Association, Project PDC-3-GU.
REsEaRCH
LP
where V = volumetric flow, cc. per second; L = length of plug, cm.; p = viscosity of gas, poise; A = cross-sectional area of cylindrical porous phig, sq. em. ; p = pressure drop between ends of plug, em.; and K = constant, characteristic of each flowmeter (8). Let subscript a refer to a base stream and b refer to a substitute stream. Then from Equation 1 vaPapb/VbMpa = 1 and one may in effect calibrate a flowmeter on one gas for all gases of known viscosity, when the calibration is practically linear. This applies also to mixtures of gases, since Bromley and Wilke (1) have recently shown that the viscosities of mixtures can be conveniently calculated from the viscosities of the components. The data in Table I show that viscosities calculated by their
Simplified Titration Vessel for Determination of Water by the Karl Fischer Method. R. Louis Menville and Samuel R. Henderson, Ethyl Corp., Baton Rouge, La. its development in 1935 the volumetric Karl Fischer S method for the determination of water has become one of the most useful techniques in the modern analytical laboratory. INCE
The extreme sensitivity of the reagent to moisture presents a problem to the analyst in maintaining a completely anhydrous titration system, especially in regions of the country where the relative humidity is fairly high during most of the year. Techniques that require removal of the stopper from the titration vessel in order to introduce the sample are not applicable if a high degree of accuracy is desired. This problem has been solved in this laboratory byavery simTable I. Comparison of Flows and Viscosities of Streams Passing through Glass-Wool ple technique involving the use Flowmeters ofaDavol Sani-Tab rubber cap. (Temperature constant within 11' C.)
I
CH4
20.06
9.92
111
63.1% CH4 36.4% CO 32.3% CHI
6 6 . 6 % CO 9 . 7 % CHI
co
C H4
14.0% H z 85.6% CO
11
a
20.06
13.03
9.92
6.48
111
179
C Ha
20.06
9.92
111
CZH4
14.62
7.27
103
CZH4
14.62
7.27
103
88.9% 87.4% CHI 12.6% Hz 74.070 CHa 26.0% Hz 53.6% CH4 46.4% Hz 2 9 . 3 7 CHI 7 0 . 7 % Hz 15.4% CH4 84.6% Hz 19.7% Hz 79.3% 35.5% Hz 64.4% CO 49.5% Hz 49.9% co 63.37% Hz 36.45% CO 85.9% Hz 14.1% CO 20.6% CzH4 79.4% CHa 78.6% CzH4 21.4% CHI 78.470 CzHr 21.6% Hz 55.370 C2H' 44.6 Hz 33.1% CZHI 66.8% Hs
co
16.68
8.28
139
14.60
7.25
160
0.96
13.41
6.66
174
0.96
20.19
9.98
111
0.99
20.08
9.98
112
1.00
20.24
10.03
112
0.99
20.80
10.35
109
0.99
22.42
11.08
103
0.96
12.98
6.44
178
1.01
13.38
6.62
175
1.00
14.05
7.00
171
0.97
15.07
7.60
163
0.96
.
0.95
18.46
9.18
134
0.94
20.63
10.28
109
1.00
14.27
7.07
105
1.00
14.21
7.05
105
1.01
13.72
6.78
108
1.01
14.00
6.93
109
0.98
All calibrations linear in range between 400- and 200-mm. water differential.
a40
The titration assembly is a 125-ml. or a 250-ml. smallmouthed Erlenmeyer flask with a magnetic stirring device. The mouth of the flask is fitted with a 1.25-inch Davol amber rubber Sani-Tab cap. With a penknife two small incisions 4 to 5 mm. wide and approximately 1.5 em. apart are made in the cap. One of these openings serves for the introduction of the tip of the Karl Fischer buret, while the other acts as a Bunsen valve to relieve pressure in the titration flask without allowing air to enter in the event a slight vacuum is created in the vessel. If the deadstop end point technique is employed, platinum wire electrodes are sealed in either side of the bottom portion of the flask with enough clearance to allow for the operation of the ma netic stirring bar. achieve complete dehydration of the flask, 5 to 10 ml. of absolute methanol is placed in the vessel and the perforated Sani-Tab cap is fitted to the neck. The tip of the Karl F i s c h e r b u r e t is i n s e r t e d through one of the slits and the water in the methanol is titrated. The flask is removed from the buret, and is carefully
40
