This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles

for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Designation: D1505 − 18

Standard Test Method for

Density of Plastics by the Density-Gradient Technique1
This standard is issued under the fixed designation D1505; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.

1. Scope* E2935 Practice for Conducting Equivalence Testing in

1.1 This test method covers the determination of the density Laboratory Applications
of solid plastics. 2.2 ISO Standard:
ISO 1183-2 Methods for Determining the Density and
1.2 This test method is based on observing the level to
Relative Density of Noncellular Plastics3
which a test specimen sinks in a liquid column exhibiting a
density gradient, in comparison with standards of known 3. Terminology
density.
3.1 Refer to Terminology D883 for definitions of other
NOTE 1—This test method is equivalent to ISO 1183-2. terms relating to this test method.
1.3 The values stated in SI units are to be regarded as the 3.2 Definitions:
standard. 3.2.1 density of plastics—the weight per unit volume of
1.4 This standard does not purport to address all of the material at 23°C, expressed as follows:
safety concerns, if any, associated with its use. It is the
D 23C , g/cm3 (1)
responsibility of the user of this standard to establish appro- NOTE 2—Density is to be distinguished from specific gravity, which is
priate safety, health, and environmental practices and deter- the ratio of the weight of a given volume of the material to that of an equal
mine the applicability of regulatory limitations prior to use. volume of water at a stated temperature.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard- 4. Significance and Use
ization established in the Decision on Principles for the 4.1 The density of a solid is a conveniently measurable
Development of International Standards, Guides and Recom- property which is frequently useful as a means of following
mendations issued by the World Trade Organization Technical physical changes in a sample, as an indication of uniformity
Barriers to Trade (TBT) Committee. among samples, and a means of identification.
2. Referenced Documents 4.2 This test method is designed to yield results accurate to
better than 0.05 %.
2.1 ASTM Standards:2
D883 Terminology Relating to Plastics NOTE 3—Where accuracy of 0.05 % or better is desired, the gradient
tube shall be constructed so that vertical distances of 1 mm shall represent
D2839 Practice for Use of a Melt Index Strand for Deter- density differences no greater than 0.0001 g/cm.3 The sensitivity of the
mining Density of Polyethylene column is then 0.0001 g/cm3·mm. Where less accuracy is needed, the
D4703 Practice for Compression Molding Thermoplastic gradient tube shall be constructed to any required sensitivity.
Materials into Test Specimens, Plaques, or Sheets
E691 Practice for Conducting an Interlaboratory Study to 5. Apparatus
Determine the Precision of a Test Method 5.1 Density-Gradient Tube—A suitable graduate with
ground-glass stopper.4
1
5.2 Constant-Temperature Bath—A means of controlling
This test method is under the jurisdiction of ASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods the temperature of the liquid in the tube at 23 6 0.1°C. A
(Section D20.70.01). thermostatted water jacket around the tube is a satisfactory and
Current edition approved April 1, 2018. Published April 2018. Originally convenient method of achieving this.
approved in 1957. Last previous edition approved in 2010 as D1505 - 10. DOI:
10.1520/D1505-18.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
Standards volume information, refer to the standard’s Document Summary page on 4th Floor, New York, NY 10036, http://www.ansi.org.
4
the ASTM website. Tubes similar to those described in Refs (1) and (2) may also be used.

*A Summary of Changes section appears at the end of this standard

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

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 D1505 − 18
5.3 Glass Floats—A number of calibrated glass floats cov- 600 mL) of the liquids to be used in the gradient tube such that
ering the density range to be studied and approximately evenly the density of the solution is approximately equal to the desired
distributed throughout this range. lowest density. When the floats are at room temperature, drop
5.4 Pycnometer, for use in determining the densities of the them gently into the solution. Save the floats that sink very
standard floats. slowly, and discard those that sink very fast, or save them for
another tube. If necessary to obtain a suitable range of floats,
5.5 Liquids, suitable for the preparation of a density gradi- grind selected floats to the desired density by rubbing the head
ent (Table 1). part of the float on a glass plate on which is spread a thin slurry
of 400 or 500-mesh silicon carbide (Carborundum) or other
TABLE 1 Liquid Systems for Density-Gradient Tubes appropriate abrasive. Progress shall be followed by dropping
System
Density Range, the float in the test solution at intervals and noting its change
g/cm3 in rate of sinking.
Methanol-benzyl alcohol 0.80 to 0.92
Isopropanol-water 0.79 to 1.00 7.2 Calibration of Standard Glass Floats (see Appendix
Isopropanol-diethylene glycol 0.79 to 1.11 X1):
Ethanol-carbon tetrachloride 0.79 to 1.59
Toluene-carbon tetrachloride 0.87 to 1.59 7.2.1 Place a tall cylinder in the constant-temperature bath
Water-sodium bromide 1.00 to 1.41 maintained at 23 6 0.1°C. Fill the cylinder about two thirds
Water-calcium nitrate 1.00 to 1.60 full with a solution of two suitable liquids selected from Table
Carbon tetrachloride-trimethylene dibromide 1.60 to 1.99
Trimethylene dibromide-ethylene bromide 1.99 to 2.18 1, the density of which can be varied over the desired range by
Ethylene bromide-bromoform 2.18 to 2.89 the addition of either liquid to the mixture. After the cylinder
and solution have attained temperature equilibrium, place the
float in the solution, and if it sinks, add the denser liquid by
NOTE 4—It is very important that none of the liquids used in the tube suitable means with good stirring until the float reverses
exert a solvent or chemical effect upon the test specimens during the time direction of movement. If the float rises, add the less dense
of specimen immersion.
liquid by suitable means with good stirring until the float
5.6 Hydrometers—A set of suitable hydrometers covering reverses direction of movement.
the range of densities to be measured. These hydrometers shall 7.2.2 When reversal of movement has been observed, re-
have 0.001 density graduations. duce the amount of the liquid additions to that equivalent to
5.7 Analytical Balance, with a sensitivity of 0.0001 g or 0.0001-g/cm3 density. When an addition equivalent to 0.0001-
better. g/cm3 density causes a reversal of movement, or when the float
remains completely stationary for at least 15 min, the float and
5.8 Siphon or Pipet Arrangement, for filling the gradient
liquid are in satisfactory balance. The cylinder must be covered
tube. This piece of equipment shall be constructed so that the
whenever it is being observed for balance, and the liquid
rate of flow of liquid may be regulated to 10 6 5 mL/min.
surface must be below the surface of the liquid in the
6. Test Specimen constant-temperature bath. After vigorous stirring, the liquid
will continue to move for a considerable length of time; make
6.1 The test specimen shall consist of a piece of the material sure that the observed movement of the float is not due to liquid
under test. The piece shall be cut to any shape convenient for motion by waiting at least 15 min after stirring has stopped
easy identification, but shall have dimensions that permit the before observing the float.
most accurate position measurement of the center of volume of
7.2.3 When balance has been obtained, fill a freshly cleaned
the suspended specimen (Note 5). Care shall be taken in cutting
and dried pycnometer with the solution and place it in the 23
specimens to avoid change in density resulting from compres-
6 0.1°C bath for sufficient time to allow temperature equilib-
sive stress.
rium of the glass. Determine the density of the solution by
NOTE 5—The equilibrium positions of film specimens in the thickness normal methods and make “in vacuo” corrections for all
range from 0.025 to 0.051 mm (0.001 to 0.002 in.) may be affected by weighings. Record this as the density of the float. Repeat the
interfacial tension. If this effect is suspected, films not less than 0.127 mm
(0.005 in.) in thickness shall be tested.
procedure for each float.
6.2 The specimen shall be free of foreign matter and voids 7.3 Gradient Tube Preparation (see Annex A1 for details):
and shall have no cavities or surface characteristics that will 7.3.1 Method A—Stepwise addition.
cause entrapment of bubbles. 7.3.2 Method B—Continuous filling (liquid entering gradi-
ent tube becomes progressively less dense).
7. Preparation of Density-Gradient Columns 7.3.3 Method C—Continuous filling (liquid entering gradi-
7.1 Preparation of Standard Glass Floats5—Prepare glass ent tube becomes progressively more dense).
floats by any convenient method such that they are fully
annealed, approximately spherical, have a maximum diameter 8. Conditioning
less than one fourth the inside diameter of the column, and do
8.1 Test specimens whose change in density on conditioning
not interfere with the test specimens. Prepare a solution (400 to
is greater than the accuracy required of the density determina-
tion shall be conditioned before testing in accordance with the
5
Manufactured certified glass floats may be purchased. method listed in the applicable ASTM material specification.

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 D1505 − 18
9. Procedure 11. Report
9.1 Wet three representative test specimens with the less 11.1 Report the following information:
dense of the two liquids used in the tube and gently place them 11.1.1 Density reported as D23C, in grams per cubic
in the tube. Allow the tube and specimens to reach equilibrium, centimetre, as the average for three representative test
which will require 10 min or more. Thin films of 1 to 2 mils in specimens,
thickness require approximately 11⁄2 h to settle, and rechecking 11.1.2 Number of specimens tested if different than three,
after several hours is advisable (Note 4). 11.1.3 Sensitivity of density gradient in grams per cubic
9.2 Read the height of each float and each specimen by a centimetre per millimetre,
line through the individual center of volume and averaging the 11.1.4 Complete identification of the material tested, and
three values. When a cathetometer is used, measure the height 11.1.5 Date of the test.
of the floats and specimens from an arbitrary level using a line
12. Precision and Bias6
through their center of volume. If equilibrium is not obtained,
the specimen may be imbibing the liquid. 12.1 Specimens Molded in One Laboratory and Tested in
Several Laboratories—An interlaboratory test was run in 1981
9.3 Remove old samples without destroying the gradient by
in which randomized density plaques were supplied to 22
slowly withdrawing a wire screen basket attached to a long
laboratories. Four polyethylene samples of nominal densities
wire (Note 6), which is conveniently done by means of a clock
of 0.92 to 0.96 g/cm3 were molded in one laboratory. The data
motor. Withdraw the basket from the bottom of the tube and,
were analyzed using Practice E691, and the results are given in
after cleaning, return it to the bottom of the tube. It is essential
Table 2.
that this procedure be performed at a slow enough rate
(approximately 30 min/300-mm length of column) so that the 12.2 Specimens Molded and Tested in Several Laboratories:
density gradient is not disturbed. 12.2.1 Samples Prepared Using Practice D4703 in Each
Laboratory—Table 3 is based on a round robin6 conducted in
NOTE 6—Whenever it is observed that air bubbles are collecting on
1994 in accordance with Practice E691, involving seven
samples in the column, a vacuum applied to the column will correct this.
materials tested by 7 to 11 laboratories. For each material, all
10. Calculation of the samples were prepared by each laboratory, molded in
accordance with Procedure C of Annex A1 of Practice D4703,
10.1 The densities of the samples may be determined
and tested using this test method. The data are for comparison
graphically or by calculation from the levels to which the
with the data of the same samples tested by Practice D2839.
samples settle by either of the following methods:
Each test result is an individual determination. Each laboratory
10.1.1 Graphical Calculation—Plot float position versus
obtained six test results for each material.
float density on a chart large enough to be read accurately to
12.2.2 Samples Prepared Using Practice D2839 in Each
61 mm and the desired precision of density. A minimum
Laboratory—Table 4 is based on a round robin6 conducted in
correlation factor of 0.995 shall be obtained to show the
1994 in accordance with Practice E691, involving seven
column is acceptable. Plot the positions of the unknown
materials tested by 10 to 15 laboratories. For each material, all
specimens on the chart and read their corresponding densities.
of the samples were prepared by each laboratory in accordance
10.1.2 Numerical Calculation—Calculate the density by
with Practice D2839. Each test result is an individual determi-
interpolation as follows:
nation. Each laboratory obtained six test results for each
Density at x 5 a1 @ ~ x 2 y !~ b 2 a ! / ~ z 2 y ! # (2) material.
where: 12.3 Concept of r and R—Warning—The following expla-
a andb = densities of the two standard floats, nations of r and R (12.3 – 12.3.3) are only intended to present
y andz = distances of the two standards, a and b, a meaningful way of considering the approximate precision of
respectively, bracketing the unknown measured this test method. The data in Tables 2-4 shall not be rigorously
from an arbitrary level, and
x = distance of unknown above the same arbitrary 6
Supporting data are available from ASTM Headquarters. Request RR:D20-
level.
1123.

TABLE 2 Precision Data Summary—Polyethylene Density

3
Material Average Density, g/cm SrA SRB rC RD
1 0.9196 0.00029 0.00106 0.00082 0.0045
2 0.9319 0.00012 0.00080 0.00034 0.0023
3 0.9527 0.00033 0.00116 0.00093 0.0033
4 0.9623 0.00062 0.00114 0.00180 0.0033
A
Sr = within-laboratory standard deviation for the indicated material. It is obtained by pooling the within-laboratory standard deviations of the test results from all of the
participating laboratories.
B
SR = between-laboratories reproducibility, expressed as standard deviation, for the indicated material.
C
r = within-laboratory repeatability limit = 2.8 Sr.
D
R = between-laboratories reproducibility limit = 2.8 SR.

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 D1505 − 18
TABLE 3 Precision Data—Density, g/cm3 TABLE 4 Density, g/cm3, Samples Prepared in Accordance With
Number Practice D2839
Density,
Material of SrA SRB rC RD Number
g/cm3
Laboratories of Density,
Material SrA SRB rC RD
B 7 0.9139 0.00029 0.00088 0.00081 0.00245 Labora- g/cm3
F 8 0.9177 0.00018 0.00079 0.00051 0.00221 tories
G 8 0.9220 0.00028 0.00071 0.00078 0.00197 B 10 0.9139 0.00026 0.00078 0.00072 0.00219
A 11 0.9356 0.00036 0.00105 0.00100 0.00294 F 12 0.9179 0.00020 0.00078 0.00055 0.00220
E 11 0.9528 0.00046 0.00118 0.00129 0.00331 G 13 0.9222 0.00030 0.00073 0.00085 0.00206
C 10 0.9619 0.00100 0.00100 0.00103 0.00281 A 15 0.9357 0.00041 0.00080 0.00115 0.00225
D 9 0.9633 0.00036 0.00137 0.00101 0.00384 E 14 0.9530 0.00039 0.00092 0.00109 0.00258
A
Sr = within-laboratory standard deviation for the indicated material. It is obtained C 11 0.9615 0.00030 0.00073 0.00085 0.00206
by pooling the within-laboratory standard deviations of the test results from all of D 10 0.9626 0.00053 0.00109 0.00148 0.00305
the participating laboratories. A
Sr = within-laboratory standard deviation for the indicated material. It is obtained
B
SR = between-laboratories reproducibility, expressed as standard deviation, for by pooling the within-laboratory standard deviations of the test results from all of
the indicated material. the participating laboratories.
C
r = within-laboratory repeatability limit = 2.8 Sr. B
SR = between-laboratories reproducibility, expressed as standard deviation, for
D
R = between-laboratories reproducibility limit = 2.8 SR. the indicated material.
C
r = within-laboratory repeatability limit = 2.8 Sr.
D
R = between-laboratories reproducibility limit = 2.8 SR.

applied to acceptance or rejection of material, as those data are 12.3.2 Reproducibility Limit, The value below which the
specific to the round robin and cannot be representative of absolute difference between two individual test results obtained
other lots, conditions, materials, or laboratories. Users of this under reproducibility conditions may be expected to occur with
test method shall apply the principles outlined in Practice E691 a probability of approximately 0.95 (95 %).
to generate data specific to their laboratory and materials, or 12.3.3 Conducting equivalence testing on numerical data
between specific laboratories. The principles of 12.3 – 12.3.3 from two sources shall be conducted in accordance with
will then be valid for each data. Practice E2935 or any known method for judging the equiva-
If Sr and SR have been calculated from a large enough body lence of two means, for example, a t-test.
of data, and for test results that were averages from testing one 12.3.4 Bias—There are no recognized standards by which to
specimen: estimate the bias of this test method.
12.3.1 Repeatability Limit, The value below which the
absolute difference between two individual test results obtained 13. Keywords
under repeatability conditions may be expected to occur with a 13.1 density; film; gradient; plaque; polyolefins; polyethyl-
probability of approximately 0.95 (95 %). ene; polypropylene; preparation

ANNEX

(Mandatory Information)

A1. GRADIENT TUBE PREPARATION

A1.1 Method A—Stepwise Addition: hydrometers, mix the two liquids in the proportions necessary to obtain
the desired solutions. Remove the dissolved air from the solutions by
A1.1.1 Using the two liquids that will give the desired gentle heating or an applied vacuum. Then check the density of the
density range, and sensitivity (S) in grams per cubic centimetre solutions at 236 0.1°C by means of the hydrometers and, if necessary, add
per millimetre, prepare four or more solutions such that each the appropriate air-free liquid until the desired density is obtained.
differs from the next heavier by 80 S g/cm3. The number of NOTE A1.2—Where aqueous mixtures are used, 0.5 % aqueous sodium
acetate shall be used to prepare the mixture. This reduces the formation of
solutions will depend upon the desired density range of the bubbles from dissolution.
column and shall be determined as follows: NOTE A1.3—In order to obtain a linear gradient in the tube, it is very
Numbers of solutions to prepare density-gradient column important that the solutions be homogeneous and at the same temperature
(Note A1.2) = when their densities are determined. It is also important that the density
difference between the solutions consecutively introduced into the tube be
~ 11D 2 2 D 1 ! /80 S (A1.1) equal.
where: A1.1.2 By means of a siphon or pipet, fill the gradient tube
D2 = upper limit of density range desired, with an equal volume of each liquid starting with the heaviest,
D1 = lower limit of density range desired, and taking appropriate measures to prevent air from being dis-
S = sensitivity, in grams per cubic centimetre per solved in the liquid. After the addition of the heaviest liquid,
millimetre. very carefully and slowly pour an equal volume of the second
NOTE A1.1—Correct the value of (1 + D2 − D1)/80 Sto the nearest heaviest liquid down the side of the column by holding the
whole number. To prepare these solutions, proceed as follows: Using the siphon or pipet against the side of the tube at a slight angle.

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 D1505 − 18
Avoid excess agitation and turbulence. In this manner, the
“building” of the tube shall be completed.
NOTE A1.4—Density gradients may also be prepared by reversing the
procedure described in A1.1.1 and A1.1.2. When this procedure is used,
the lightest solution is placed in the tube and the next lightest solution is
very carefully and slowly “placed” in the bottom of the tube by means of
a pipet or siphon, which just touches the bottom of the tube. In this manner
the “building” of the tube shall be completed.
A1.1.3 If the tube is not already in a constant-temperature
bath, transfer the tube, with as little agitation as possible, to the
constant-temperature bath maintained at 23 6 0.1°C. The bath
level will be equal to or greater than the solution in the tube,
and provision shall be made for vibrationless mounting of the
tube.
A1.1.4 For every 254 mm of length of tube, dip a minimum
of five clean calibrated floats, spanning the effective range of
the column, into the less dense solvent used in the preparation
of the gradient tube and add them to the tube. By means of a
stirrer (for example, a small coiled wire or other appropriate
stirring device) mix the different layers of the tube gently by
stirring horizontally until the least dense and most dense floats
FIG. A1.1 Apparatus for Gradient Tube Preparation
span the required range of the gradient tube. If, at this time, it
is observed that the floats are “bunched” together and not
spread out evenly in the tube, discard the solution and repeat
the procedure. Then cap the tube and keep it in the constant-
where:
temperature bath for a minimum of 24 h.
VA = starting liquid volume in Beaker A,
A1.1.5 At the end of this time, plot the density of floats VB = starting liquid volume in Beaker B,
versus the height of floats to observe whether or not a fairly dA = density of the starting liquid in Beaker A, and
smooth and nearly linear curve is obtained. Some small dB = density of the starting liquid in Beaker B.
irregularities may be seen, but they shall be slight. A minimum A small excess (not exceeding 5 %) over the amount
correlation factor of 0.995 shall be obtained to prove linearity indicated by the preceding equality will induce the required
of the column. Whenever an irregular curve is obtained, the flow from AtoBand yield a very nearly linear gradient column.
solution in the tube shall be discarded and a new gradient
A1.2.2 Place an appropriate volume of the denser liquid into
prepared. In the event a column is disturbed in a manner which
Beaker Bof suitable size. Prime the siphon between Beaker-
causes a bead or beads (top or bottom, one or two) to give a bad
Band the gradient tube with liquid from BeakerBand then close
correlation factor, that bead or beads height may be removed
the stopcock. The delivery end of this siphon shall be equipped
from the correlation chart as long as the sample to be analyzed
with a capillary tip for flow control.
does not fall within that range. There must be four consecutive NOTE A1.6—Techniques acceptable for transfer of liquid into the
beads in correlation. The minimum correlation factor shall be gradient tube are siphon/gravity, vacuum-filling, use of a peristatic pump,
0.995. or any other technique useful to transfer liquids in a controlled manner. It
is important to control the flow in order to maintain a desirable gradient.
NOTE A1.5—Gradient systems may remain stable for several months.
A1.2.3 Place an appropriate volume of the less dense liquid
A1.2 Method B—Continuous Filling with Liquid Entering into Beaker A. Prime the siphon between Beakers A and B with
Gradient Tube Becoming Progressively Less Dense: the liquid from Beaker A and close the stopcock. Start the
highspeed, propeller-type stirrer in Beaker B and adjust the
A1.2.1 Assemble the apparatus as shown in Fig. A1.1, using speed of stirring such that the surface of the liquid does not
beakers of the same diameter. Then select an appropriate fluctuate greatly.
amount of two suitable liquids which previously have been
carefully deaerated by gentle heating or an applied vacuum. A1.2.4 Start the delivery of the liquid to the gradient tube by
Typical liquid systems for density-gradient tubes are listed in opening the necessary siphon-tube stopcocks simultaneously.
Table 1. The volume of the more dense liquid used in the mixer Adjust the flow of liquid into the gradient tube at a very slow
(Beaker Bshown in Fig. A1.1) must be equal to at least one half rate, permitting the liquid to flow down the side of the tube. Fill
of the total volume desired in the gradient tube. An estimate of the tube to the desired level.
the volume of the less dense liquid required in BeakerAto NOTE A1.7—Preparation of a suitable gradient tube may require 1 to
establish flow fromAtoBcan be obtained from the following 11⁄2 h or longer, depending upon the volume required in the gradient tube.
inequality:
A1.3 Method C—Continuous Filling with Liquid Entering
V A .d B V B /d A (A1.2) Gradient Tube Becoming Progressively More Dense:

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 D1505 − 18
A1.3.1 This method is essentially the same as Method B
with the following exceptions:
A1.3.2 The lighter of the two liquids is placed in Beaker B.
A1.3.3 The liquid introduced into the gradient column is
introduced at the bottom of the column. The first liquid
introduced is the lighter end of the gradient and is constantly
pushed up in the tube as the liquid being introduced becomes
progressively heavier.
A1.3.4 The liquid from Beaker A must be introduced into
Beaker B by direct flow from the bottom of Beaker A to the
bottom of Beaker B, rather than being siphoned over as it is in
Method B. Filling the tube by this method may be done more
rapidly than by Methods A or B. The stopcock between
Containers A and B shall be of equal or larger bore than the
outlet stopcock. A schematic drawing of the apparatus for
Method C is shown in Fig. A1.2.

FIG. A1.2 Apparatus for Gradient Tube Preparation

APPENDIX

(Nonmandatory Information)

X1. FLOAT CALIBRATION—ALTERNATIVE TEST METHOD

X1.1 This test method of float calibration has been found by X1.1.3 Vary the bath temperature until the solution density
one laboratory to save time and give the same accuracy as the is very near to that of the float. (If the float was initially on the
standard test method. Its reliability has not been demonstrated bottom of the graduate, lower the bath temperature until the
by round-robin data. float rises; if the float floated initially, raise the bath tempera-
X1.1.1 Prepare a homogeneous solution whose density is ture until the float sinks to the bottom.)
fairly close to that of the float in question. X1.1.4 Change the bath temperature in the appropriate
X1.1.2 Fill a graduate cylinder about 3⁄4 full with the direction in increments corresponding to solution density
solution, drop in the float, stopper, and place in a thermostatted increments of about 0.0001 g/cm3 until the float reverses
water bath near 23°C. Fill a tared two-arm pycnometer with the direction of movement as a result of the last change. This must
solution. Place the pycnometer in the bath. be done slowly (at least 15-min intervals between incremental

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 D1505 − 18
changes on the temperature controller). Read the volume of X1.1.6 Remove the pycnometer from the bath, dry the
liquid in the pycnometer. outside, and set aside until the temperature reaches ambient
X1.1.5 Change the bath temperature in increments in the temperature. Weigh and calculate the “in vacuo” mass of
opposite direction, as above, until a change in the float position solution to 0.0001 g. Using the average of the two observed
again occurs. Read the volume of liquid in the pycnometer. solution volumes, calculate the density of the solution to
0.0001 g/cm3. This solution density is also the float density.
NOTE X1.1—The float should rise off the bottom of its own volition. As
a precaution against surface tension effects when the float is floating, the X1.1.7 The pycnometer used shall be calibrated for volume
float should be pushed about halfway down in the liquid column and then from the 23°C calibration, although the reading is taken at a
observed as to whether it rises or falls. For this purpose, a length of different temperature. The alternative test method is based on a
Nichrome wire, with a small loop on the lower end and an inch or so of number of unsupported assumptions but generally gives the
length extending above the liquid surface, is kept within the graduate
throughout the course of the run. To push a floating float down, the same results as that described in 7.2 within the accuracy
cylinder is unstoppered and the upper wire end grasped with tweezers for required. In case of disagreement, the method described in 7.2
the manipulations. The cylinder is then quickly restoppered. shall be the referee method.

REFERENCES

(1) Anfinsen, C., “Preparation and Measurement of Isotopic Tracers: A Gradient Tube in the Study of High Polymers,” Journal of Polymer
Symposium Prepared for the Isotope Research Group,” Edwards, J. Science, JPSCA, Vol 1, 1946, p. 249.
W., Publishers, Ann Arbor, MI, 1946, p. 61. (8) Tessler, S., Woodberry, N. T., and Mark, H., “Application of the
(2) Wiley, R. E., “Setting Up a Density Gradient Laboratory,” Plastics Density-Gradient Tube in Fiber Research,” Journal of Polymer
Technology, PLTEA, Vol 8, No. 3, 1962, p. 31. Science, JPSCA, Vol 1, 1946, p. 437.
(3) Linderstrøm-Lang, K., “Dilatometric Ultra-Micro-Estimation of (9) Low, B. W., and Richards, F. M., “The Use of the Gradient Tube for
Peptidase Activity,” Nature,NATRA, Vol 139, 1937, p. 713. the Determination of Crystal Densities,” Journal of the American
(4) Linderstrøm-Lang, K., and Lanz, H., “Enzymic Histochemistry XXIX Chemical Society, JACSA, Vol 74, 1952, p. 1660.
Dilatometric Micro-Determination of Peptidase Activity,”Comptes (10) Sperati, C. A., Franta, W. A., and Starkweather, H. W., Jr., “The
rendus des gravaus de laboratorie Carlsberg, Serie Chimique, Vol 21, Molecular Structure of Polyethylene V, the Effect of Chain Branch-
1938, p. 315. ing and Molecular Weight on Physical Properties,” Journal of the
(5) Linderstrøm-Lang, K., Jacobsen, O., and Johansen, G., “Measurement American Chemical Society, JACSA, Vol 75, 1953, p. 6127.
of the Deuterium Content in Mixtures of H2O and D2O,” ibid., Vol 23, (11) Tung, L. H., and Taylor, W. C., “An Improved Method of Preparing
1938, p. 17. Density Gradient Tubes,” Journal of Polymer Science, JPSCA, Vol
(6) Jacobsen, C. F., and Linderstrøm-Lang, K.,“Method for Rapid Deter- 21 , 1956, p. 144.
mination of Specific Gravity,” Acta Physiologica Scandinavica, (12) Mills, J. M., “A Rapid Method of Construction Linear Density
APSCA, Vol 1, 1940, p. 149. Gradient Columns,” Journal of Polymer Science, Vol 19, 1956, p.
(7) Boyer, R. F., Spencer, R. S., and Wiley, R. M., “Use of Density- 585.

SUMMARY OF CHANGES

Committee D20 has identified the location of selected changes to this standard since the last issue (D1505 - 10)
that may impact the use of this standard. (April 1, 2018)

(1) Removed permissive language where needed.

(2) Corrected statements in 12.3.1, 12.3.2, and 12.3.3 to make
definitions consistent with ASTM Committee E11 on Statistics.

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