A methyl bromide dispenser for use in the fumigation of quarantined products

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Material Information

Title:
A methyl bromide dispenser for use in the fumigation of quarantined products
Physical Description:
Mixed Material
Creator:
Cain, Charles A
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine ( Washington, D.C )
Publication Date:

Record Information

Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030345525
oclc - 781639057
System ID:
AA00017459:00001


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ET-156 February 1940

United States Department of Agriculture
Bureau of Entomology and Plant Quarantine


A METHYL BROMIDE DISPENSER FOR USE IN THE FUMIGATION
OF QUARANTINED PRODUCTS


By Chas. A. Cain, Division of Japanese Beetle Control


As a means of facilitating the fumigation of quarantined
plant products with methyl bromide as a basis for certification, a
dispenser that accurately measures small quantities of gas used in
fumigation chambers has been developed.

Methyl bromide is a gas at ordinary temperatures, its boiling
point being 40.1 F. As a liquid it has a specific gravity of
1.732 and as a gas it is approximately 3.5 times as heavy as air.

The dispenser described herein consists essentially of two
," angle valves, one -1" brass vent cock, one *" pipe cross, three
close nipples, a -" to X" close pipe coupling, a 1-01 steel grease
cup with the cap bored out to l-*" to accommodate the glass measuring
tube, three *" pipe to -" copper tubing fittings, a 75-ml. gauge
glass tube with a low coefficient of expansion and a rolled rim,
a -1" copper syphon tube, and polyvinyl alcohol gaskets, as indicated
in figure 1.

Methyl bromide is supplied in steel cylinders of various
capacities and under pressure, to keep it in a liquid form. In
this form it can readily be measured in a graduated glass tube.
However, immediately upon releasing the pressure the liquid will
volatilize and can no longer be measured by this means at tempera-
tures above 40 F. To overcome this factor, the dispenser was
designed to admit liquid under pressure from the supply cylinder.
Venting the excess air and gas in the dispenser lowers the tem-
perature sufficiently, by the passage of methyl bromide from a high
to a low pressure, to fill the glass with the liquid. Very little
gas is wasted in this procedure, and, if a refilling of the dis-
penser is necessary, the dispenser need not be vented the second
time.

After the glass tube is filled, the supply valve on the
dispenser (fig. 1) is closed, as well as the vent valve. The
discharge valve on the dispenser remains closed during the filling
of the dispenser. As the temperature begins to rise the gas in





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the head of the dispenser expands and exerts a downward pressure
on the column of liquid in the glass tube. To discharge the gas
in the dispenser it is only necessary to open the discharge valve,
and the gas pressure will force, the liquid up through the syphon
tube and out through the discharge valve into the fumigation
chamber.

Construction of the apparatus is accomplished through the
assembly of ordinary pipe fittings. The copper tubing and fittings
may be purchased at an automobile accessory store. The glass tubing
is a stock item wherever scientific glassware is manufactured. At a
small additional cost it is possible to have the gauge glass tube
graduated in cubic centimeters, allowing for the displacement of
the syphon tube. Polyvinyl alcohol is used for gasket material at
the points indicated by No. 7 in figure 1. It is not absolutely
necessary to use it in the packing glands of the two angle valves,
but it makes a safer job. A 11" I.D. steel grease cup is used
for a packing gland to seal the glass measuring tube. The gasket
and the grease cup cap are then slipped over the glass tube and
screwed on the valve assembly, hand tight. Polyvinyl alcohol
gaskets can be made with a leather belt punch out of sheet stock
*" thick.

The total cost of the apparatus, excluding labor, is approxi-
mately $4.50.

The assembled dispenser and supply cylinder are shown in
figures 2 and 3.




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low 1 1/611 Globe Valves
C Z 1/8" Vent Cock, bras
7 ~ 2.
7__ 03 1/0" pipe cross
-- |4 1/6" close nip,.Les
"" 5 1/4" to 1/8" Couplii4;
i 6I 1 steel grease cup 1i
^ r7 PolyviiLyl alcohol gts.;et
8 1-1/8" OD gauge glass,
9.1 |0 | rolled edge, round boitoi,
-1 |. -- ,choice or e.raduutiun 0 to
o 75 c. c.
9 Syphon tube of 1/8"
i 5. copper tubing
Bj U "- 10 Copper tubin& couplii.;
'1. i/6" pipe, 1/*" tubing
1 11 Copyer tubing 1/4"





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SFigure 1.-Details
1 of the dispenser.



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Digitized by the Internet Archive
in 2012 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://archive.org/details/methy00unit





































Figure 2.-Close-up view of the dispenser
and supply cylinder.


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Figure 3.--Disuenser and cylinder in position on the
top of a fumigating box.


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