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Патент USA US2129275

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_- Sept. 6, 1938.
HARTZ’ELL ET AL
2,129,275
FUMIGATI on '
Filed Jan. _ 9'; 1934
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INVENTQRS
BY‘
’
'
-
ATTORNEYS
.
2
2,129,275
rated solution or a solution containing an ex
cess of fumigant is employed the gas will be sat
urated with fumigant vapors at equilibrium.
When solutions containing amounts of fumigant
less than those required for saturation are em
ployed, the concentration of fumigant in the gas
at equilibrium will be substantially proportional
tion by any suitable means, for example, by a
' fan.
The degree of concentration of the fumigant in
the air will, at equilibrium, be dictated by the
concentration‘ of the-fumigant in the solid solu
tion. Thus, if the solid solution is saturated with
or contains an excess of.fumigant, the current
of air will be saturated, at equilibrium, with
The choice of an appropriate solvent for the‘ fumigant vapor. Similarly, if the solid solution
10 naphthalene necessitates a consideration ofthe is 50% saturated with fumlgant, the current of 10
requirements that such a solvent must meet. air, at equilibrium, will be approximately 50%
"to the percentage saturation of the solution.
' The vapor pressure of the solvent should be very
low, preferably not greater than 0.1 mm. at room
. temperature; otherwise thelarge volumes of gas
15 passed through or in contact with the solution
will remove a considerable quantity'of solvent
along with the naphthalene. The solvent vapors
‘should not betoxic to plants or harmful to other
substances to be preserved in the concentration
.20 which the partial pressure of the solvent will
build up in the current of air. The solubility of
the fumigant in the solvent ought to be consid
erable so that the removal of the furnigant during
the fumigation will not greatly alter the original
concentration. The solvent must not corrode
the metal parts of the apparatus in which it is
used. It should be inexpensive and readily ob
tained in quantity upon short notice. Hygro
scopic qualities are undesirable since dilution
might occur through they accumulation of water.
Many of these qualities are found in certain pe
troleum hydrocarbons, such as the light motor
oils. The solubility of naphthalene in an oil with
an S. A. vE. rating of 20 is about ten per centby
weight.
.
While any enclosure may be successfully'fumi
gated by the process of the invention, we‘ have
found that greenhouses represent one type of
enclosure for. the fumigation of which the proc
es of the present invention is’ particularly well
adapted. For this reason, the following descrip
v 45.
tion of the process will refer principally to the
fumigation of greenhouses, but it readily will be
seen that other enclosures may be fumigated in
substantially the same manner. By way of ex
ample, air will be considered to be the gas to be
charged with fumigant.
Naphthalene hasbeen found to be a fumigant
which is well adapted for use in the processes
50 and apparatus described herein, and particular
reference will, therefore, be made to the use of
this substance as the fumigant. ' It will be under
stood, however, that by such reference we do not
intend to limit ourselves to the use of naphtha
Ca M
lene, for other fumigants having suitable prop
erties are known to those familiar with the art, '
andmay be obtained upon the market in com
mercial quantities.
'
saturated with fumigant vapor. Since the con
centration of fumigant in the air at saturation
is a substantially de?nite determinable quantity,
it-is apparent that if the concentration of the 15
fumigant in the solid solution is ?xed at a pre
determined value, the maximum theoretical con
centration of fumigant vapor in the current of
air may be adjusted to any desired value. The
principles here involved are those obtained from ‘
a studyvv of the partial pressures of the‘ vapors
above a solid solution.
The solid'solution itself may be prepared by
melting together a fumigant, such as naphtha
lene, and a suitable solvent or diluent, in ap
propriate predetermined proportions.
_We;have found that sulphur is very satisfac
tory as the diluent._ When using sulphur and
naphthalene, the two are mixed together in suit
able proportions and melted. The molten prod
uct is preferably stirred, and is then poured into
pans and allowed to cool. The solid solution re
sulting from vthe freezing of the melt is broken up
into small pieces to provide a large surface for
vaporization of the naphthalene, and is intro 36.
duced into the container through which the at
mosphere of the greenhouse is to be circulated.
Although ‘for many purposes a solid solution
is suitable, it is frequently found that the great
er ?exibility and easeof control of liquid solu
tions render their use in the fumigation of en
closures advantageous. In preparing a liquid so- .
lution, the fumigant, such as naphthalene is dis
solved to an appropriate concentration in a
suitable liquid diluent or solvent.
We have found that a solution of 5 percent or
more by weight of naphthalene in a‘ suitable
petroleum hydrocarbon will produce satisfactory
results. Air, after passing in contact with a solu
tion of this composition retained in a suitable
apparatus, will exhibit e?lcient fumigating char
acteristics.
'
A suitable apparatus for the use of a liquid
solution, ‘such as naphthalene dissolved in a
petroleum hydrocarbon, is illustrated, partially
in section, in the single ?gure of the, accompany
ing sheet of drawings.
Within a container ll, open at the top, is dis
posed a chamber ll bounded by walls It, the
lower end portions of which are disposed adja
cent the floor II of the container, and the upper
end portions of which are disposed adjacent'a
0d of the invention, the solid solution is first pre
mid-portion
of the container II. A circumam
pared and broken into small pieces. These small bient reservoir
I4 is thereby formed between the.
pieces are then supported upon trays or shelves '
inner
‘surfaces
of the walls of the container
within ‘a._suitabl,e receptacle, and air is passed and the outer surfaces
of the walls II of the
over them. In this manner, the fumigant is
vaporized from the solid solution, and vapors of
Above the upper ends of the walls I 2 of the
ifumigant are carried off by the current of air chamber II is disposed a plate ll, substantially
and with it are introduced into the greenhouse conical in shape, the apex of which points up
or other enclosure to be fumigated,
wardly substantially along the center line of the
The air to be charged with ffumigant vapor is chamber II. The periphery of the plate II ex
‘preferably that comprising vfiche"-atmosphere of tends beyond the outer surfaces of the walls I!
In utilizing a solid solution as the substance by
60 means of which vapors of fumigant are-intro
duced into the atmosphere of the enclosure to be
[fumigated in accordance with a preferred meth-'
chamber.
u- the greenhouse, and it fis'd'rawn'into and forced
throughtlie receptacle containing the solid 8011.1
.
.
‘
>
of the chamber. ' The under surface of the
plate is supported sufliciently far above the up
arrears
'
'
ever,
resides
in
the
fact
that
the
atmosphere
of
per ends of the walls it to provide an aperture,
or series of apertureal? between the upper ends
of the walls l2 and the undersuriace of the plate
i5.
Arranged at a suitable distance above the
plate iii are a plurality of ?lters ll, constructed
of cheesecloth or other appropriate material,
which serve to catch entrained droplets of-liquid
which might be carried upwardly by the rising
10 current of air.
‘
A conduit in Eonnects the interior of the cir?
cumambient liquid reservoir M at the ?oor i3
with the intake of a pump it, and the discharge
of the pump is connected by a conduit 2! with
15 another conduit 22, which passes through a wall
of the container it. The conduit 22 is provided
with a downwardly curved portion 23 which
serves to discharge liquid passing through the
conduit directly over the apex of the conical
plate‘ It.
20
.
A fan 2% communicates with the interior of
the chamber ill, and serves to draw the atmos
phere in the vicinity of the fan through the in
take 25 and to force it, upwardly through'the
chamber
ii.
-
‘
In using the above-described apparatus, .a. so»
lution of fumigant in a suitable liquid diluent
is introduced into the circumambient reservoir,
approximately to a depth indicated by the liquid
level L. The centrifugal pump 20 is started and
the solution begins to circulate through the ape
' .paratus, passing through the conduit it, the
the greenhouse may be continually circulated
through the apparatus without fear of obtain- 1
ing too high a degree of concentration of fumi
gant in the atmosphere,‘ and this in turn is owing
to the particular qualities of the solution used.
.As described above, a solution of naphthalene
in a petroleum hydrocarbon, such as a light mo
tor oil, will yield satisfactory results, but those
familiar with the art will readily discern that 10
other fumigants may be dissolved in other dil
uents, withoutdeparting from the spirit ofthe
present invention or the scope of the appended
claims. The following discussion of theoretical
and experimental results will be concerned with 15
a solution of naphthalene dissolved in a petrole
um hydrocarbon, which comprises a presently
preferred solution.
'
A solution of 5% by weight of naphthalene in
a light motor oil represents approximately a
one-half saturated solution. If the similarity in
chemical nature of the solute and solvent justify
the assumption of a perfect solution, then the
partial vapor pressure of naphthalene over the
solution is one-half the vapor pressure over pure
naphthalene, which at room temperature is ap
proximately (l.1 mm. A greenhouse witha capac
ity of 6000 cubic feet requires, then,
name-2
X 128 X
24.6
58.2 grams of naphthalene
to buildup an equilibrium concentration of naph
thalene in the atmosphere (The gram molecular
pumpZd and the conduits 2i and 22, and emerg
volume at 30° C. is 24.6 liters and one cubic foot
ing from the curved portion 23 of the conduit 22 ' equals 28.3 liters. The molcular weight of naph 35
to fall upon the upper surface of the conical
35
is 123.)
plate id in the vicinity of its apex. By the force - thalene
In greenhouse practice we have found that a
, of gravity, the solution runs down the upper sur
face of the conical plate, and falls ‘as a rain
from the periphery thereof to the body of the so
40 lution con?ned within the circumambient reser
voir.
‘
,
Meanwhile the fan 24 has been started and air.
is being drawn through the intake and is being
forced upwardly through the chamber H. Upon
reaching the upper portion of the chamber, the,
air is deflected outwardly through the apertures
it by the under surface of the conical plate.
‘higher concentration than 5% of naphthalene in
oil will be required due to the inevitable leakage
of air which constantly dilutes the equilibrium
mixture. The fact that about 1.5 pounds of naph
thalene are removed from‘ the solution in the
course of a fumigation, lasting from about 13 to
16 hours, indicates the extent of this loss. Con
sequently, the initial concentration of naph
thalene 'in the oil may advantageously be made
as high as 8 or 9 percent in some instances.
The concentration of the solution is readily
Thence it passes through the rain of solution ‘ adjusted by adding naphthalene ?akes and run
falling from the periphery of the plate, and‘ in ning the pump for a few minutes to circulate the 50
so doing, is charged with fumigant which is va»
porized from the solution.
'
The air, nowcharged with fumigant and car
rying also entrained droplets of solution, con
oil and bring about solution. During the course
of our experiments, the original solutions were
generally prepared from ‘7.5 gallons of oil and d
pounds of naphthalene, resulting in a solution
. tinues its upward journey and passes through the of 6.8 percent naphthalene by weight. Determi 55
55 ?lters ill. Here the entrained droplets of solu ' ‘nations of the speci?c gravity of the solution were
tion are mechanically removed from the current ‘made at the start and conclusion of each run in
of air, and collect upon the fabric of the ?lter, order to establish the amount of naphthalene '
‘from which they drip after ‘coalescence into
larger drops.
60
‘
The fumigant-charged air, free from' entrained
consumed.
‘
,
_
. As an indication of the suitability of the in_
60
vention herein described for the fumigation of
droplets of solution, is discharged into the at
greenhouses, , the following experimental pro
mosphere of the enclosure in which the apparatus ~ cedure and results are herewith presented.
is placed through the open top of the contain
Some preliminary laboratory experiments were
er ill.
'
performed with oil solutions containing various 65
A consideration of the apparatus above-de percentages
of naphthalene. Leaves infested with
scribed will indicate that it possesses certain ad-. red spider mite (Teiranychus ielarius L.) were
vantages which render it eminently‘suitable for con?ned in a shallow glass vessel in which was
thefumigation of greenhouses. For example, it also placed an open dish of the oil solution. These
may belcompactly constructed, and 11! mounted experiments are listed in Table I and show that 70
upon wheels, may be readily moved through the complete control was obtained with solutions
aisles of the greenhouse to any part thereof. It containing 5% or more of naphthalene by weight.
is entirelyself contained, requiring only a con
In some cases a dessicator, arranged so that both
nection with a source of electric current to drive
the small motors, which themselves drive the fan
and the pump. The greatest advantage, how
the oil andv air were stirred, was used to insure
equilibrium conditions.
.
75
-
4
8,1?39375
I
Tim I
_
-
_
-
mite (Tarsonemus pallidus Bks.), the onion
thrips (Thrips tabaci Lind), or the black grain
Results of laboratory tests on red spider mite ea:
‘
'
. is more diilloult to eradicate than the cyclamen
posed tonavhthalene dissolved in oil
thrips (Heliothrips femoralis Reuter) . Counts of
living and dead mites were made 24 hours after
Percent naphthalene by weight N21226: N333" Pair?“
treatment.
5
15
4
16
45
52
4
27
.87
2
14
88
3
x
0
2
44
12
100
86
0
. 38
100
0
0
20
3B
100
100
0
0
17
20
100
100
90 '
We have found that commercial fumigation oi
_
.
Tests with solid solutions of naphthalene and
sulphur, the content of which ranged from 20
to 90"percent of naphthalene.'indicated that a
solid solution containing 90 percent naphthalene
and 10 percent sulphur could be used without
injury to the foliage of the most sensitive plants
tested (Table 11). Similarly, no foliage injury
was observed on plants fumigated by means of
the naphthalene-oil method at the concentrations 15
reported in Table II. Marigold, calendula, cos- '
_ mos, carnation, and hydrangea were fumigated
while in bloom without injury to the ?owers.
'
Table 11
20
Percentage control of red Sz?der mite by naphtha
’
Expomre to
Percent
naphthalene
narhtha-
vapors, hours
-
one
lene W170i‘
7
Temperature
-
"'
Relative
humidity,
Maximum Minimum
-
,
°F.
°F.
percent
'
Nmm
bol, of
s
i_
Ter
cent
control
ens‘
Naphthalene-sulphur
N
so
78
86
B5
68
88
88'.
179
502
95
99
90
_ 7o
‘ so
es
200
99
~ I)
74
70
as
see
so
25
80
76
85
115
so
75
84
82
72
68
88
80
212
115
80
89 35
93
75
100
, 68
88
229
91
76
100
100
100
89
100
68
80
68
.88
60
88
204
253
200
90
99
100
Naphthalene oil
0. 7
95
0. 6
7. 9
69
80
9. 5
100
'
65
.......... __
211
89
62 .......... __
__________ -_
222
250
96
100
77
200
100
70
greenhouses is entirely practicable by the use oi
The percent of mites killed ranged from 95 to
100 when-solid solutions of naphthalene (90 per—
we append the following experimental results, ob- “ cent) and sulphur (10 percent) were used. Solid
the present invention, and by way of example
tained under the conditions given.
v ' solutions made up of lower percentages of naph
Fumigations were begun either at 4 p. m. or at
thalene were not effective, while pure naphtha
lene was impractical because of injury to foliage.
5 p. m. and continued until 619.. m.. 8 a. m. or 9
a; m'., depending on whether periods of 13, 14, 15 )
or 16 hours’ duration were desired. Greenhouse
sections of a capacity of 6000 cubic feet were
fumigated. The plants were grown in pots or in
?ats and were watered before the fumigation was
started, inasmuch as experience has shown that
a high relative humidity is desirable to avoid in-‘
jury to the foliage. The most favorable tempera
ture range for fumigation was found to be be
v‘Equally successful fumigations were obtained
with the liquid'solution method.
1
Plants infested with a species of Tarsonemus
mite resembling the cyclamen mite,.the speci?c
identity of which has not yet been established,.
were included in a number of fumigations. This
species seems to have about the same tolerance
for naphthalene vapor as the cyclamen mite and
was readily eradicated at the concentration re
' i'
'
.
‘
quired to kill the red spider mite.
The diil‘iculty of detecting analytically‘ the con
We claim:
.
65 centration of naphthalene vapor in air led to the
1. The .method of fumigating an enclosure
use of tomato plants, of the variety Bonny Best. which comprises preparing a solid solution com
and buckwheat as test plants, which investiga ' prising a fumigant and a diluent in such pro
- tion had shown would indicate the maximum and portions that the vapor pressure of the fumigant
minimum concentrations respectively. for satis-' is adjusted to a predetermined value, passing a
70 factory control of the red spider mite, and at the gas in contact with the solid solution to charge 70
same time would be ‘.ithin the tolerance limit of *the gas with the fumigant, and introducing the
- other‘ plants commonly grown in greenhouses.
fumigant-charged gas into the enclosure to be
tween 68" F. and 80° F.
_ ‘Th red spider mite-was selected-as a suitable
fumigated.
'
g
test species for the eiilciency of a given fumiga-‘i -2. The method of fumigating an enclosure
75 tion as previous investigation had shown‘ that'it which comprises preparing a solid solution com 75
2,129,275 '
prising a fumigant and sulphur in such propor
tions that the vapor pressure of the fumigant
is adjusted to a predetermined value, passing a
gas in contact with the solid solution to charge
the gas with the fumigant, and introducing the
fumigant-charged gas into the enclosure to be
fumigated.
',
_ ’
3. The method of fumigating an enclosure
~ which‘ comprises preparing a solidsolution com
15
non-toxic to the plants to be fumigated, adjust- ing the proportion of fumigant to diluent in the
solution so that the vapor pressure of the fumi
gant over the solution corresponds substantially
‘to the maximum'partial pressure of fumigant
vapor which it is desired to build up in the at
m'osphere of the greenhouse, passing a gas in
contact with the liquid solution to charge the gas.
with the fumigant, and introducing the fumi
10
gant~charged gas into the greenhouse.
prising naphthalene and sulphur in“ such pro-g
7. The method of fumigating an enclosure
portions that the vapor pressure of the naphtha
lene is adjusted to a predetermined value, pass - which comprises preparing a solution compris
ing a gas incontact with the solid solution to ing naphthalene and a petroleum ‘hydrocarbon
charge the' gas with naphthalene vapors, and having a vapor pressure at room temperature not
introducing
the naphthalene vapor-charged gas substantially greater than 0.1 mm.,v adjusting the
15
proportion of naphthalene to petroleum hydro-w
into the enclosure to be fumigated.
4. The method of funiigating a greenhouse carbon in the solution so that the-‘vapor pres
'which comprises. circulating the atmosphere
sure of the naphthalene over the solution corre
within the greenhousein contact with a solution ' sponds substantially to the maximum partial
20 comprising a fumigant and a non-toxic diluent
in such proportions that the vapor pressure of.
thefumigant over the solution corresponds sub
stantially to the maximum partial pressure of
fumigant vapor‘ which it is desired to build up
in the atmosphere of the greenhouse.
5. In the fumigation of enclosures with a fumi
gant-charged gas, the method of controlling the
' concentration of the fumigant in the gas which
comprises preparing a solution comprising the
fumigant and a non-toxic diluent in such pro- '
portions that the vapor. pressure of the fumigant
pressure of naphthalene‘vapor which it is de 20
sired to build up in the enclosure tobe fumi
gated; passing a ‘gas in contact with the solution
to charge the gas with naphthalene vapors,'and
introducing the naphthalene vapor-charged gas
into the enclosure to be fumigated.
i 25
8. A method of maintaining substantially con
stant the concentration of a fumigant in the at
mosphere of an enclosure being fumigated which ,
comprises continuously withdrawing the atmos-'
phere of the enclosure from the enclosure, pass 30
ing it in contact with a solution comprising a
' over the solution corresponds substantially to ~f-umigant and a diluent in such proportion that
' the maximum partial pressure of fumigant vapor the vapor pressure of the iumigant over the so
which it is desired to build up in the gas, and then 1 lution corresponds substantially vto the maximum
passing a gas in contact with the solution to partial pressure of fumigant vapor desired in the 35
charge the gas with the fumigant.
6. The method'of fumigating plants in a green
house which comprises preparing a liquid solution
comprising a fumigant and a diluent, the vapors
of which at room temperature are substantially
40
atmosphere of the enclosure, and re-introducing
the atmosphere into the enclosure.
ALBERT HARTZELL.
FRANK WILCOXON.
WILLIAM J. YO‘UDEN.
40
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