A SIMPLE GAS-FLOW METER
HASKELL S. TUBIASH, M.S.P.H.
Plum Island Animal Disease Laboratory, Animal Disease and Parasite Research Division, United Stales
Department of Agriculture, Greenport, Long Island, New York
dish or tray (B). A 6-mm. glass tube, Ucurved at the lower end (C), is inserted the
entire length of the graduate and adjusted so
that the lip of the inverted graduate allows
Many laboratory procedures, such as
air-scrubbing, aeration of microbiologic cultures, and technics with membrane filters,
require knowledge of the volume of air en-
FIG. 1. Diagram of gas-flow meter. The tube at the upper right leads to the source of the
'iicuum.
tering the system. A simple, inexpensive
gas-flow meter has been devised which may
be assembled readily by use of universally
available laboratory equipment. Any installed vacuum line, water pump, or mechanical vacuum-pressure pump may be used
to aspirate air or other gases through this
meter.
DESCRIPTIVE
DETAILS
A graduated cylinder of appropriate size
(A) is inverted in a large glass crystallizing
Received, April 10, 1958; accepted for publication June 9.
Mr. Tubiash is a Microbiologist.
clearance for the tubing. Water is added to
the crystallizing dish, and the level is adjusted so that it is even with the calibration
of the graduate. A pressure-tubing connection with a plastic disconnective fitting (D)
is made to the desired experimental
apparatus (X), and also from the apparatus
to the source of the vacuum. As the pump
removes air, water rises in the graduate and
a direct volume per time reading may be
made by use of the graduate calibrations
and a stop-watch. At the end of the desired
time interval, the flow of gas is clamped on
the positive side of the disconnective fitting,
and the line is disconnected. A reading of air
replaced by water is taken from the calibra-
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340
Vol. 30
TUBIASH
TABLE 1
FRITTED GLASS DISPERSION
TUBE
Air Aspirated
Vacuum
22-gage needle
20-gage needle
in. of Ilg
ml./mitt
ml./miti.
1
2
3
5
8
10
15
20
25
8
115
215
370
510
605
720
770
775
50
460
555
900
1280
1450
1670
1780
1790
the rate of flow. A convenient reducing valve
may be constructed by the use of a 1-ml.
Luer-lok syringe barrel with the shoulder
removed and fitted with a 20- or 22-gage
needle. This device may be inserted in the
system by means of piercing a rubber stopper
at a suitable point (F) and attaching the
vacuum line, or it may be inserted direct]}'
into the line.
A Gast vacuum-pressure pump fitted with
aneroid vacuum and pressure gages was
used as a vacuum source. A supplemental
mercury manometer (M) was also used for
greater accuracy in reading vacuums at
lower levels.
RESULTS
TABLE 2
MILLIPORE FILTER—AA
GRADE
Air Aspirated
22-gage needle
in. of Ilg
ml./min.
1
2
3
5
8
10
15
20
25
125
250
335
490
620
690
810
850
850
20-gage needle
ml./min.
360
655
760
1290
1530
1660
1930
1965
2110
tions on the graduate. The increasing head of
water rising in the graduate (A) has no
appreciable effect on the rate of flow of the
gas during the test period.
If the procedure warrants, a trap (E) is
inserted in order to protect the pump. If the
source of the vacuum is not otherwise
gauged, a mercury manometer (M) should
be inserted in the line. For precise control,
a restriction or needle-valve may be introduced between the test apparatus and the
pump (or trap, if used), in order to reduce
Using 20- and 22-gage needles as reducing
valves, and aspirating air through nutrient
broth by means of a fritted glass dispersion
tube (G) fitted into an N P N digestion tube,
readings were obtained as listed in Table 1.
With an AA-grade Millipore filter in a 47mm. holder, readings were as listed in Table 2.
SUMMARY
A rapid, inexpensive method of determining the flow rate of gas through a system
by the use of a simple gas-flow meter is
presented. The meter may be constructed
of ordinary pieces of laboratory equipment
universally available in biologic, chemical,
or physical laboratories.
SUMMARIO
IN
INTERLINGUA
Es presentate un rapide e incostose
methodo pro determinar le intensitate del
fluxo de gas a transverso un date systema
per medio de un simple mesurator del fluxo
de gas. Le mesurator pote esser construite
ex pecias ordinari de equipamento laboratorial que es universalmente disponibile
in laboratories biologic, chimic, o physic.