BREATHALYZER R TESTS WITH THE EQUILIBRATOR AND THE

BREATHALYZER R TESTS WITH THE EQUILIBRATOR AND THE
EFFECT OF ROOM TEMPERATURE.
A.E. WELLS
ROYAL CANADIAN MOUNTED POLICE CRIME DETECTION LABORATORY
HALIFAX, CANADA
INTRODUCTION
Ontario was the first province in Canada to use the
Breathalyzer , beginning in August, 1956. The city of
Vancouver started operations in June, 1957 and soon after,
the Royal Canadian Mounted Police began a program in the
province of Saskatchewan. By 1967, the program had
expanded to all of Canada. Since the program's earliest
beginnings, very strict controls have been maintained
over operational procedure (1).
One of the controls has been that the accuracy of the
evidentiary breath testing instrument must be checked
each time a person is tested. For this purpose the
2
R.C.M.P. program has used an equilibrated aqueous alcohol
solution. The solution will impart alcohol to air pumped
through the solution and the alcohol-laden air is
analyzed. The amount of alcohol in the air will depend
on the degree of equilibration, the concentration of
1.
2.
In Canada, "Breathalyzer" is a registered trade
mark of Robert Frank Borkenstein - Registration
No. 108,824 (December, 1957; renewed December, 1972).
The unqualified word "alcohol" in this paper means
ethyl alcohol.
699
alcohol in the solution, and the temperature of the
3
solution. The Equilibrator , the device used to generate
the sample, has a finely sintered gas dispersion stone
which ensures the sample is equilibrated. The concentration
of alcohol in the solution is kept constant. The solution
is not maintained at a constant temperature so it will
vary with room temperature. Since dilute aqueous alcohol
solutions obey Henry's Law up to at least 1 %w/v (2), the
amount of alcohol imparted to the air passing through the
solution should depend only on the temperature of the
solution. The accuracy of the Breathalyzer is confirmed
by comparing the actual reading with the expected one.
Present standards (1) require the test result to be with­
in - 10 mg%
of the expected value.
This paper will deal with two aspects of the Standard
Alcohol Solution test. One aspect will be to determine
the effect of a room-solution temperature differential on
the accuracy of the test. However, a pre-requisite will
be to determine if the expected readings currently being
used are accurate. To date, the table of values given in
the Breathalyzer Instruction Manual (3) has been used.
Several publications have dealt with the partition ratio
of alcohol between water and air at different temperatures.
The other aspect of this paper will be to compare the
expected readings in the Breathalyzer Instruction Manual
with those predicted from data in the scientific
literature.
All statistical analyses used are based on methods
recommended by the United States Department of Commerce National Bureau of Standards (4).
3.
Smith & Wesson (Canada) Ltd., Mississauga, Ontario -
4.
Part Number 003-0007-000.
Breathalyzer readings in this paper are expressed in
the units: mg alcohol per 100 ml blood, or as
abbreviated:
700
mg%.
EXPECTED BREATHALYZER READINGS ON AQUEOUS ALCOHOL SOLUTIONS.
Table 1 summarizes most of the published data dealing
with the k a /#w (Ostwald *partition ratio of alcohol between
air and its aqueous solution) values determined experi­
mentally. It includes the data of Dobson (5), Harger et
al (2), Foote and Scholes (6), Grosskopf (7), Thomas (8),
Wrewsky (9), and Jones (10). The data of Haggard and
Greenberg (11) and Haggard et al (12) have not been
included since these results are so grossly different from
all the other data. Haggard (12) stated the results
published in 1934 are in error and it is probably safe to
assume the possibility of error in the 1941 results. It
seems unlikely that these results are correct and all the
other data are wrong.
A plot of the temperature (T) against the natural
logarithm of ^a/w x 10 3 is ahown in Figure 1 (using the
data in Table 1). If linear regression can be assumed
for these data sets, an exponential equation can be
calculated relating
, to T (in °C):
6 k a/w
k /
a/w
=
0.0000415
e0*0658 T
(Equation 1)
M
Dubowski has reported similar values of 0.00004155 x
0.06591
T (13), 0.00004156
n nnno/.r/ e0.06575 T (reported
/
. , in
.
e
private communication January, 1979) and 0.00004145 x
/+/\
,T .
.
j • j in
• 4
-ue0.06583 T (14).
Using
an equation
derived
this
manner, partition ratios for all temperatures in the
15 - 40 °C range may be calculated. These calculated
ratios may then be used to calculate expected Breathalyzer
readings when using an aqueous alcohol solution of known
concentration and temperature.
Before proceeding, it is necessary to determine if
these calculated ratios will be an accurate reflection of
the k < values obtained experimentally.
To determine
J
a/w
K
this, two questions must be considered:
(i) Is the relationshipr between T and ka/w
, functional
701
or statistical?
(ii) Is the assumption of linear regression between
T and ln ka/w
# Jjustified?
A functional relationship assumes there is an exact
mathematical formula which relates the two variables and
the only reason the experimental data do not exactly fit
this equation is error in measuring one or both variables.
For a statistical relationship, the assumption is that
there is only a statistical association between the two
variables and that there is no exact mathematical relation­
ship between them. There should be no doubt that a
functional relationship
exists between ka/w
, and T (for a
v
purely statistical relationship, the correlation coef­
ficient for the data in Figure 1 is 0.9989).
With respect to the second question, Dubowski (14)
stated that a direct relationship does exist over the
short temperature ranges for simulators and equilibrators.
However, statistical analysis shows that the array means
(the average value of ln k 3 //W for each T) do not lie in a
straight line (Fq
for (5, 21) degrees of freedom is
2.68; F calculated from the data in Figure 1 is 13.6).
A review by Franks and Ives (15) suggested that
several abnormalities may exist in dilute aqueous solutions
of the lower alcohols (including ethyl alcohol). Negative
deviations from Raoult’s Law are observed in very dilute
solutions. At low temperatures, the volatility of the
alcohol increases with concentration more than predicted
.
by Henry's Law. At higher temperatures, the opposite
occurs. Although the data of Knight (16) suggests there
are no major effects of this nature at concentrations
below 0.01 mole fraction, the conclusion of Franks and
Ives in the review mentioned above is probably sound;
that is, as stated by Scatchand (17):
"The best advice which comes from years of study of
liquid mixtures is to use any model in so far as it helps,
but not to believe any moderately simple model corresponds
very closely with any real mixture".
702
It would be imprudent, without sufficient jus­
tification, to suggest that the deviation from linearity
is due to experimental error. In fact, the very similar
results obtained by different authors would tend to
suggest the opposite.
A better fit to the experimental data is obtained
from the second order equation:
k , = 0.0000326 e(0.0840 T
a/w
(Equation 2)
-
0.000318 T2)
Table 2 compares the values of k / calculated from
a/w
Equation 1, Equation 2, and the average experimental
values (from Table 1). The values calculated from
Equation 2 are all within - 1 x 10-^ of the experimental
range. It should be noted that all values from Equation
2 fall within 2s of the experimental range while the
values calculated by Equation 1 for 15, 30, and 40 °C do
not.
In Table 3, a comparison is made between the expected
readings for a Standard Alcohol Solution test calculated
from Equation 2 and those presented in the Breathalyzer
Instruction Manual. Readings were calculated for an
alcohol solution containing 3.38 mg/ml (the value currently
being used in Canada).
EFFECTS OF R00M-S0LUTI0N TEMPERATURE DIFFERENCES
1.
GENERAL
Since the Standard Alcohol Solution test is the
Breathalyzer technician’s assurance that the instrument is
functioning properly at the time of the test, there should
be no chance that the instrument produces as apparently
correct result that arises from a combination of two or
more errors. For example, assume the Breathalyzer mal­
functions and reads falsely high. Secondly, assume the
703
correct reading for the Standard Alcohol Solution test is
lower than anticipated from measuring the temperature.
The combination of these two errors could theoretically
produce an apparently correct response. For driving
offences there would not be as much concern if the reverse
happened (the Breathalyzer would have to be reading falsely
low which would be to the benefit of the person being
tested).
Figure 2 is a schematic diagram of the equilibrator.
The thermometer is graduated to 0.2 C but can be read
to 0.1 °C. The immersion mark is near the top of the
equilibrator where the bottle starts to taper. When taking
a sample, the technician is instructed to maintain a head
of foam on the solution up to the immersion mark of the
thermometer. The clear, plastic liquid trap is used as a
precaution against liquid entering the Breathalyzer in the
event that the foam is accidentally pumped too high and
passes into the outlet tube.
In this paper, T^ designates the room temperature,
T 2 is the temperature of the solution near the mercury
reservoir of the thermometer, and To is the temperature
at the air-solution boundary.
There are two possible effects of a room-solution
temperature difference on the Standard test:
(1) The effect on the temperature of the solution.
Two factors to be considered here are:
(i) Heating or cooling effect of the air passing
through the solution. The heat capacity
(C ) of air at 25 C is approximately 0.240
P
_i _i
cal deg
g . If 2 liters of this air are
passed through a Standard Alcohol Solution
which is at 20 °C, the air would only add
3 cal to 100 ml solution. This would raise
the temperature of the solution by only
0.03 C. In other words, unless very extreme
temperature differences occur, the temp­
erature of the air going in the solution
704
will have a negligible effect.
(ii) Heat transfer through the walls of the
equilibrator bottle. The heating (or
cooling) effect will depend on the value of
(T.. - T 2 ), the amount of air pumped through
the solution (effectively stirring the
solution) and the thermal conductivity of
the bottle . Earlier studies with an
equilibrator indicate that if (T.. - T 2 ) is
greater than 1 C but less than 5 C° and
3 liters of air are pumped through the
solution, the change in temperature of the
solution is approximately 0.1 C°.
(2)
The effect on the temperature and alcohol con­
tent of the air leaving the solution. If T ^ < T 2 ,
a temperature gradient will be produced in the
foam above the solution such that T^< T o < T 2 »
The final partition of alcohol from the liquid
to the vapour phase will occur at T^. The result
is that the vapour being analyzed will contain
less alcohol than predicted by measuring T 2 .
Another factor to be considered is that the
temperature of the outlet tube will be close to
T^ so that condensation will occur. One liter of
air above a 3.38 mg/ml aqueous alcohol solution
at 30 °C will contain 30 mg water and 1.05 mg
o
alcohol. On cooling to 25 C , 7 mg water will
condense. By knowing the total amount of alcohol
available for distribution between air and water
(1.05 mg) and knowing k ^ w for 25 °C, it is pos­
sible to calculate the alcohol concentration of
the condensate. In this case, the loss of
alcohol from the vapour phase would be 3 °L (the
5. Wells, A.E. (1977),
unpublished report.
705
concentration of alcohol in the condensate
would be approximately 460 mg%). Similarly, if
the air is cooled from 30 C to 20 °C, a loss of
7.5 7o could occur. For cooling from 25 °C to
20 C, the loss is approximately 3.5 7».
For the reverse situation where T ^ > T 2 , the
temperature gradient will be such that T ^ > T 2 > T ^
with the final partition of alcohol from the
liquid to the vapour phase again occuring at T~.
In this case, condensation will not be a factor.
2.
EXPERIMENTAL
Apparatus (i)
(ii)
Breathalyzer Model 900A. Accuracy of the
instrument was checked using a Smith & Wesson
Simulator and aqueous alcohol solution of 122
mg70. A series of 10 tests gave an average
result of 99.0 mg°L (s = 0.50). The instrument
was checked periodically throughout the
experimental runs to check calibration.
Certified thermometers (Brooklyn Thermometer Co.
Inc.). Two thermometers (ranges of 9.00 - 21.00
°C and 19.00 - 31.00 °C with 0.01 °C divisions)
were supplied with certificates stating they had
been calibrated according to NBS Test No. 199114
with all temperatures based on IPTS-68. Correction
factors were supplied.
(iii)
Equilibrator (Smith % Wesson (Canada) Ltd.). The
only modification to the equilibrator was that
the standard thermometer was removed and two
thermocouples were inserted. These were used to
measure T 2 and T^. The equilibrator was then
sealed at the top to prevent leaking.
706
(iv)
BAT-8 Digital Thermometer (Bailey Instrument Co.)
with PT-6 sensors. The sensors were checked for
accuracy and found to read within 0.1 °C from one
sensor to another. Additionally, the sensors
would read within 0.1 C of the certified ther­
mometer for at least 10 minutes after calibration.
The sensors were used to measure T^, T 2 , To, and
the temperature of the water bath.
(v)
Thelco Model 183 Water Bath (GCA Precision
Scientific). The water bath could be heated and
maintain temperatures which cycled over less
than a 1 °C range. For sub-ambient data, a
cooling coil was used.
Reagents (i) Standard Alcohol Solution (BDH Chemicals, Lot
Number 807001). This solution is supplied in
100 ml aliquots. A random sample was analyzed
(modified Widmark procedure) and found to con­
tain 3.41 mg/ml (manufacturer stated 3.41 mg/ml
both by redox and gas chromatography). After
analysis, the solutions were stored at 4 °C and
removed just prior to use.
(ii)
(iii)
Simulator solution. This solution was prepared
by placing 31 ml of absolute alcohol (Consolidated
Alcohols Ltd., Toronto) in 20 liters water
(distilled in glass). Analysis by modified
Widmark procedure showed 122 mg% (theoretical
122.3 mg7o) . The solution was stored at 4 C and
500 ml aliquots were removed just prior to use.
Potassium dichromate solution (BDH Chemicals,
Lot Number 802565). Analysis of a random sample
of ampoules indicated they were suitable.
707
3.
PROCEDURE
Standard Alcohol Solution (100 ml) was placed in the
equilibrator and the equilibrator was immersed in the water
bath such that the surface of the solution was level with
the surface of the water bath. Temperatures
(room),
T 2 (solution), and T^ (air-liquid boundary) were measured
using the digital thermometer. The temperature of the
water bath was measured using both the certified ther­
mometer and the digital thermometer. In this manner the
digital thermometer could be calibrated to the certified
thermometer prior to each test.
Temperatures T^ and the temperature of the water bath
were adjusted to the desired temperatures. With T 2 equal
to the temperature of the water bath, room air was pumped
through the solution (approximately 2 liters of air per
test) into the Breathalyzer at a rate that would maintain
a level of foam on the solution up to where the immersion
mark of the thermometer would normally be (near the tapered
top of the bottle).
Temperatures T^, T 2 , and T^ were recorded and the
result of the Breathalyzer test was determined.
A maximum of four tests was conducted on each solution.
4.
DATA
A total of 36 tests were conducted where the room
temperature was below the solution temperature. These
results are presented in Table 4.
There were 34 tests conducted where the room
temperature was above the solution temperature. These
results are given in Table 5.
A plot of 7o A R£ (the percentage difference between the
actual and expected readings) against AT 2 is presented in
Figure 3. A positive aL AR^ means the actual reading was
higher than expected.
708
5.
DISCUSSION OF EXPERIMENTAL RESULTS
When a technician is performing a Standard Alcohol
Solution test, he would measure T 2 • Therefore, ARg is
the measure of the difference between the actual test
result and that expected by the technician. It should be
remembered that all of ARg may not be related to A T 2
(the manufacturer's stated accuracy is - 10 mg% although
actual measurements with the Breathalyzer demonstrate
that, in most cases when properly calibrated, it is
capable of analyzing a Standard Alcohol Solution to with­
in - 5 mg?o of the anticipated result).
Condensation is not a factor in Table 5. Therefore,
the AR-p values should average "0" over a series of
tests if A T 2 is not a factor. Three other possible
explanations why this is not the case are:
(i) The calculated expected values are inaccurate.
(ii) Temperature measurements are inaccurate.
(iii) The Standard Alcohol Solution test, because of
the procedure involved or the calibration of the
Breathalyzer, tends to overestimate the actual
reading.
The temperature measurements were accurate to with­
in 0.1 C so this should not be a factor. The expected
results are calculated using Equation 2. If Equation 1
were used, values of 75 mg7o for 15 °C, 77 mg7o for 15.5 °C,
80 mg7o for 16.0 °C, and 83 mg79 for 16.5 °C are obtained.
These would demonstrate better agreement between the
theoretical and experimental results but the results would
Still be biased to the positive side. The Breathalyzer
used was shown to be calibrated to within 170 of the
anticipated result using the simulator. Finally, there is
a tendency for the Standard Alcohol Solution to slightly
underestimate, rather than overestimate, the actual reading.
Therefore, it is probably a valid conclusion that A T 2 is
having an effect on the results.
For Table 4, all AR£ values fall within those pre709
dieted if the effect of condensation is considered. Since
the technician measures T 2 , the AR^ values in Table 4 are
most significant. It should be noted that in only 3 tests
does A Rg exceed 10 mg7o when AT 2 is less than 10 C°. It
should also be noted that the maximum ARg is -16 mg%
occuring when A T 2 is 10.6 C°. For all tests in Table 4,
condensation was evident in the outlet tube and the clear,
plastic trap attached to the equilibrator.
SUMMARY
Part of this paper has dealt with the accuracy of the
expected readings from Standard Alcohol Solution tests as
presented in the Breathalyzer Instruction Manual. The data
of Jones verifies the results of earlier investigations.
The relationship between T and In kflyw appears to be non­
linear over the 15 - 40 °C range. An equation which best
describes the relationship between T and In k , can be
v
a/w
used to calculate expected Breathalyzer readings which
show no significant deviation from those presented in the
Breathalyzer Manual.
The effect of the room-solution temperature difference
has been examined and discussed. In general, experimental
results agree with predicted ones except some bias appears
to be introduced by the temperature difference.
Since the technician's primary concern should be that
the breath test instrument is not reading falsely high, it
is paramount that the Standard Alcohol Solution test will,
under all conditions, indicate any possibility of this
occurrence. Tables 4 and 5 show that the only time that
it could falsely indicate the instrument to be functioning
properly is when the room temperature is considerably
lower than the solution temperature. In all these cases,
condensation was evident in the outlet tube and trap of
the equilibrator.
710
CONCLUSIONS
1.
The best relationship between k , and solution
o
a
temperature (in C) for dilute aqueous alcohol
solutions in the 1 5 - 4 0 C range is:
k j
a/w
=
0.0000326 e^0 *0840 T “ 0 ‘000318 T )
2.
The table of expected readings given in the
Breathalyzer Instruction Manual is accurate for
aqueous alcohol solutions of 3.38 mg/ml.
3.
Tests conducted with the room temperature higher
than the solution temperature will give results
higher than expected.
4.
Tests conducted with the room temperature lower
than the solution temperature will give results
lower than expected.
5.
If room temperature is not being measured, the outlet
tube of the equilibrator should be checked to ensure
there is no condensation present.
711
REFERENCES
1.
7.
8.
9.
10.
Recommendations of the Canadian Society of Forensic
Science on Breath Testing Standards and Procedures,
(1969), Canadian Society of Forensic Science Journal,
2(4), 88-93.
Harger, R.N., Raney, B.B., Bridwell, E.G. and
Kitchell, M.F., (1950), J. Biol. Chem. 183(1), 197213.
"Breathalyzer Model 900A Instruction Manual", Smith
and Wesson, Springfield, Mass., U.S.A., Copyright
1973.
"Experimental Statistics", United States Department
of Commerce, National Bureau of Standards - Hand-rbook 91 (reprinted October, 1966) L.C.C. 63-60072,
Dobson, J.E., (1925), J. Chem. Soc., 127, 2866.
Foote, H.W., and Scholes, S.R., (1911), J. Am. Chem.
Soc., 33, 1309.
Grosskopf, K., (1954), Angewandte Chemie, 66, 295.
Thomas, R., (1922), J. Soc. Chem. Ind., 41, 34.
Wrewsky, M., (1912), Z. physik. Chem., 81, 1.
Jones, A.W., (1974), Ph. D. Thesis, University of
11.
Cardiff, Wales.
Haggard, H.W. and Greenberg, L.A., (1934), J.
12.
Pharmacol. Exp. Ther., 52, 150.
Haggard, H.W., Greenberg, L.A., Miller, D.P., and
13.
Carroll, R.P., (1941), J. Lab. Clin. Med., 26, 1527.
Dubowski, K.M., (1979), abstracts - Toxicology Sec.,
2.
3.
4.
5.
6.
15.
16.
p. 155, American Academy of Forensic Sciences Meet­
ing, Atlanta, Georgia, U.S.A.
Dubowski, K.M., (1979), J. Analytical Toxicology,
3, 177-182,
Franks, F. and Ives, D.J.G., (1966) Quart. Rev., 20, 1.
Knight, W.S., (1962), Ph. D. Thesis, Princeton
17.
University.
Seatphard, G., (1949), Chem. Rev., 44, 7.
14.
712
Table 1.
Published data on the distribution of alcohol
o
between air and water (expressed
as
k
»
x
10
).
r
a/w
'
Investigators
Temperature
15
Dobson
Harger et al
Foote & Scholes
Grosskopf
Thomas
Wrewsky
Jones
0.107
20
0.155
25
0.215
0.217
(
30
0.310
o
C)
35
0.418
37
40
0.470
0.562
0.481
0.565
0.210
0.106
0.158
0.158
0.155
0.313
0.212
0.212
0.217
0.216
0.313
0.305
0.416
0.426
0.469
0.466
0.566
0.555
713
Table 2.
Average experimental ka / #W and those calculated
from Equations 1 and 2.
3
k , x 10
a/w
Temperature
~
( C)
Experimental
Equation 1
15
0.107
0.111*
0.107
20
0.157
0.155
0.154
25
0.214
0.215
0.218
30
0.310
0.299*
0.304
35
0.420
0.415
0.418
37
0.472
0.473
0.472
40
0.562
0.577*
0.564
* Values more than 2s from the experimental range.
714
Equation 2
Table 3.
Comparison of expected readings from the
Breathalyzer Manual with those calculated
from Equation 2.
Temperature
( °C)
Breathalyzer
Manual
Equation 2 *
20.0
105
104
21.0
112
112
22.0
120
121
23.0
130
130
24.0
140
140
25.0
150
150
26.0
160
161
27.0
173
173
28.0
185
186
29.0
200
199
30.0
215
213
* Calculated for a 3.38 mg/ml solution.
715
Table 4.
*
T1
25.4
25.0
25.0
25.5
25.7
25.3
25.3
25.4
23.9
24.0
24.4
24.3
18.3
17.9
17.8
18.4
17.5
17.0
Results with room temperature lower than
solution temperature.
**
ATi
AT2
4.5
4.6
4.9
4.5
4.3
4.6
4.6
4.4
4.5
3.9
2.8
2.6
10.0
10.8
4.7
5.2
10.9
10.6
11.6
12.0
5.1
4.6
4.4
4.7
4.7
4.6
4.9
4.0
2.9
2.6
10.6
11.3
11.5
11.0
11.9
12.4
are
- 9
-14
- 5
- 4
- 7
- 5
- 7
- 8
-12
- 5
- 6
-10
-16
-10
-12
- 9
-13
- 9
A R ' ++
E
T1
*T1
AT2
6
5
2
2
18.0
18.2
14.0
18.5
11.1
11.0
13.7
7.6
- 5
- 4
- 6
- 5
- 7
- 4
- 5
-10
- 8
- 3
- 4
- 4
- 9
- 6
15.2
14.4
16.5
14.8
15.9
16.0
16.4
15.5
16.1
16.5
15.3
14.6
15.4
14.3
9.5
9.5
8.5
9.2
8.1
8.1
7.8
8.6
7.3
7.4
8.8
8.5
8.6
9.6
11.6
11.5
14.4
7.9
9.7
9.6
8.6
9.3
8.5
8.3
7.9
8.7
-
7.5
7.5
9.0
8.7
8.7
9.7
are
- 9
-13
-15
-12
-
0
3
5
7
8
4
3
1
7
-
5
9
6
8
6
Room temperature.
** The difference between the temperature at the air/solution
boundary and the room temperature.
***The difference between the room and solution temperatures.
+ Actual reading less the reading expected for T 2 •
++ Actual reading less the reading expected for T^.
*
716
AR'
E
- 2
- 6
-10
-10
+ 2
- 2
- 4
- 6
- 4
0
0
0
-
5
4
7
4
7
5
Table 5.
*
T1
21.6
21.7
21.8
21.9
23.0
22.1
23.3
23.9
23.0
24.0
22.3
22.6
22.0
22.4
22.1
21.6
22.5
*
**
Results with room temperature higher than
solution temperature.
**
1
-5.6
-5.9
-5.9
-6.0
-7.0
-6.2
-7.1
-7.7
-6.8
-7.7
-5.9
-6.3
-5.7
-6.0
-5.4
-4.7
-5.6
AT2
-5.8
-6.0
-5.9
-6.1
-7.1
-6.3
-7.3
-7.8
-6.9
-7.9
-6.1
-6.4
-5.8
-6.1
-5.5
-4.9
-5.6
are
7
5
6
7
6
7
9
9
10
9
6
4
5
3
5
5
5
AR]
5
5
6
6
5
6
8
8
9
7
5
3
4
3
4
4
5
T1
AT1
22.6
22.3
22.2
24.4
24.4
24.6
25.0
25.0
25.6
25.0
25.5
25.0
25.6
24.4
26.0
25.5
24.5
-5.8
-5.8
-6.1
-9.1
-8.7
-8.7
-9.1
-9.0
-9.5
-8.6
-9.3
-9.0
-9.5
-8.3
-9.8
-9.4
-8.4
at2
-5.7
-5.9
-6.2
-9.2
-8.8
-8.9
-9.3
-9.1
-9.6
-8.7
-9.3
-9.1
-9.6
-8.4
-9.9
-9.5
-8.5
a
AR
Re
6
7
5
6
6
6
9
7
8
6
7
9
10
10
12
10
11
5
6
5
5
5
5
8
6
8
6
6
8
10
10
11
10
11
Room Temperature.
The difference between the temperature at the air/solution
boundary and the room temperature.
**■*■ The difference between the room and solution temperatures.
+
++
Actual reading less the reading expected for T 2 .
Actual reading less the reading expected for T^.
717
T (°C )
20
>
30
■
40
a
z
1.0 -
n
©
K
U|
X
n = 28
2. 0 -
Figure 1.
Relationship between the partition ratio of
alcohol (between air and its aqueous solution)
and temperature (in
718
C).
C lear
P la stic Trap
A ir Pump
T h erm om eter
Gas D ispersion
Stone
gure 2.
The Equilibrator (Smith & Wesson (Canada) Ltd.).
720
Figure
3.
between
the difference
in room
and
solution
temperatures
and
the percentage difference between the actual and expected Breathalyzer
readings (a positive AT 2 means the room temperature was higher than the
solution temperature; a positive °L A R^ means the actual result was higher
than the expected result).
Relationship