ASTM D5032-97

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 5032 – 97
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Maintaining Constant Relative Humidity by Means of
Aqueous Glycerin Solutions
This standard is issued under the fixed designation D 5032; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope salt solutions or various strength sulfuric acid-water systems.
1.1 This practice describes a method for obtaining constant
4. Significance and Use
relative humidity ranging from 30 to 98 % at temperatures
4.1 Controlled relative humidity environments are impor-
ranging from 0 to 70°C in relatively small containers by means
tant for conditioning materials for shelf-life studies or for
of an aqueous glycerin solution.
investigating the change in physical or dielectric properties
1.2 This practice is applicable for closed systems such as
after exposure.
environmental conditioning containers.
4.2 The use of aqueous-glycerin solutions reduces the pos-
1.3 This practice is not recommended for the generation of
sibility of contamination of the materials or corrosion of
continuous (flowing) streams of constant humidity unless
electrode systems which would be more likely to result from
precautionary criteria are followed to ensure source stability.
saturated salt or acid water solutions.
1.4 This standard does not purport to address all of the
4.3 Applicable material specifications should state the ex-
safety concerns, if any, associated with its use. It is the
posure conditions, including time, temperature and relative
responsibility of the user of this standard to establish appro-
humidity, that a material should be subjected to before subse-
priate safety and health practices and determine the applica-
quent testing. Typical conditions are given in Practice D 618.
bility of regulatory limitations prior to use.
5. Apparatus
2. Referenced Documents
5.1 Container, airtight, of a material not acted upon by
2.1 ASTM Standards:
copper sulfate (or with the glycerin solution contained in a tray
D 618 Practice for Conditioning Plastics and Electrical
2 made of a material not acted upon by copper sulfate).
Insulating Materials for Testing
5.2 Refractometer, covering the range of 1.33 to 1.47
D 4023 Terminology Relating to Humidity Measurements
(sodium) with an accuracy of 0.0003.
E 104 Practice for Maintaining Constant Relative Humidity
by Means of Aqueous Solutions
6. Glycerin Solution
2.2 Other Documents:
6.1 Use a good industrial grade of glycerin (“high gravity”
DIN50008 “Konstantklimate uber wasserigen Losungen”
and “dynamite” grades are satisfactory) in distilled water.
(Constant Climates Over Aqueous Solutions)
Calculate the concentration in terms of the refractive index,
Part 1: Saturated Salt and Glycerol Solutions
4 (R), at 25°C for the desired relative humidity at any tempera-
Part 2: Sulfuric Acid Solutions (1981)
ture between 0 and 70°C as follows:
3. Summary of Practice
2 2 2
R 5 ~=~100 1 A! 1 A 2 ~H 1 A! 2 A! 1 1.3333 (1)
715.3
3.1 Controlled relative humidity environments are gener-
ated using mixtures of glycerin and water.
where:
3.2 Practice E 104 contains methods for maintaining con-
T 5 temperature of the solution, °C,
stant relative humidity environments using aqueous saturated 2
A 5 25.60 − 0.1950T + 0.0008T , and
H 5 relative humidity, percent.
1 6.1.1 This will give the desired relative humidity with an
This practice is under the jurisdiction of ASTM Committee D-9 on Electrical
and Electronic Insulating Materials and is the direct responsibility of Subcommittee accuracy of 60.2 % at a constant temperature of 25°C. At other
D09.12 on Electrical Tests.
constant temperatures, the error, if any, may increase with the
Current edition approved Mar. 14, 1997. Published January 1998. Originally
deviation of the temperature from 25°C. The relative humidity
e1
published as D 5032 – 90. Last previous edition D 5032 – 90 (1995) .
values at 0, 25, 50 and 70°C for a number of refractive index
Annual Book of ASTM Standards, Vols 08.01 and 10.01.
Annual Book of ASTM Standards, Vol 11.03.
values are given in Table 1. Obtain the refractive index for
Available from Deutsches Institut fur Normung, 4-10 Burggrenzenstrasse
intermediate values of relative humidity and temperature by
Postfach 1107, D-1000 Berlin, Federal Republic of Germany. Also available from
plotting curves from the values in the table or by calculating
American National Standards Institute, Publication Office, 1430 Broadway, New
York, NY 10018. from the above formula.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 5032
TABLE 1 Relative Humidity Over Glycerin Solutions
as small as practical as there will be a continual loss of vapor
Refractive Relative Humidity, % through the vent. Check the concentration of the solution
Index
periodically and adjust if necessary in this case.
0°C 25°C 50°C 70°C
at 25°C
7.1.3 Make the surface creepage distance between the
1.3463 97.7 98.0 98.2 98.4
solution and the material being conditioned long enough to
1.3560 95.6 96.0 96.4 96.7
1.3602 94.5 95.0 95.5 95.8 prevent the solution creeping to the material being conditioned.
1.3773 89.2 90.0 90.7 91.2
7.2 Temperature Fluctuations:
1.3905 84.0 85.0 85.9 86.6
7.2.1 Avoid temperature fluctuations. Best results are ob-
1.4015 78.8 80.0 81.1 81.8
1.4109 73.7 75.0 76.2 77.0
tained in a controlled temperature room where the average
1.4191 68.6 70.0 71.3 72.2
temperature is constant and the fluctuations are of relatively
1.4264 63.4 65.0 66.4 67.3
short duration. Cover the container to shield from drafts. Drafts
1.4329 58.4 60.0 61.4 62.5
1.4387 53.3 55.0 56.5 57.6
may cause temperature differences inside the container. Chang-
1.4440 48.3 50.0 51.5 52.6
ing ambient temperature causes a temperature difference be-
1.4486 43.3 45.0 46.6 47.7
1.4529 38.3 40.0 41.6 42.7 tween that of the solution and the air above it. As a rule,
changes in the solution temperature lag behind that of the air in
the container. This results in a low humidity with rising
6.2 To prevent fungus growth in the solution, add about
temperature an
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