The term density is the mass of a substance per unit volume. The symbol most often used for density is ρ, and sometimes the letter D can also be used. Mathematically, density is defined as mass divided by volume:
- ρ = m/V
Where m = mass of the substance, V = volume.
Density is measured in g/cm3 or kg/m3.
The density of a substance is influenced by a variety of factors, such as pressure or temperature. They have little influence for most solid materials, but there's a significant effect on the density of solids and liquids.
Density is calculated depending on the type of material:
- Homogeneous materials: The density at all regions of a homogeneous object equals its total mass divided by its total volume.
- Heterogeneous materials: The density varies between different regions of the object. The density of heterogeneous materials is calculated by determining the densities of many small volumes around various locations of the said material.
- Non-compact materials: Materials such as flakes, pellets, granules or powders contain voids, such as air, water or other fluids. The density of such materials is determined by multiple methods, such as pycnometer method or mathematical expressions for various geometric shapes.
List of densities
Common densities
| Material |
Density (kg/m3) |
Notes
|
| Hydrogen
|
0.08988
|
At 0 °C and 101.325 kPa
|
| Helium
|
0.146
|
At 300 K and 101.325 kPa
|
| Aerographite
|
0.2
|
The air inside is excluded
|
| Ammonia (gas)
|
0.73
|
At 1.013 bar at 15 °C
|
| Neon (gas)
|
0.9
|
At 0 °C and 101.325 kPa
|
| Metallic microlattice
|
0.9
|
The air inside is excluded
|
| Aerogel
|
1.0
|
The air inside is excluded
|
| Air
|
1.2
|
Standard conditions
|
| Oxygen (gas)
|
1.308
|
At 300 K
|
| Fluorine (gas)
|
1.696
|
0 °C and 101.325 kPa
|
| Argon (gas)
|
1.784
|
0 °C and 101.325 kPa
|
| Nitrous oxide (gas)
|
1.8724
|
At 15 °C and 1.013 bar
|
| Butane
|
2.489
|
At 20 °C and 1.013 bar
|
| Chlorine (gas)
|
3.2
|
0 °C and 101.325 kPa
|
| Krypton (gas)
|
3.749
|
0 °C and 101.325 kPa
|
| Xenon (gas)
|
5.894
|
0 °C and 101.325 kPa
|
| Radon (gas)
|
9.73
|
0 °C and 101.325 kPa
|
| Tungsten hexafluoride (gas)
|
12.4
|
Standard conditions
|
| Freon 12 (gas)
|
36.83
|
Standard conditions
|
| Liquid hydrogen
|
70
|
At –255 °C
|
| Styrofoam
|
75
|
Average type of styrofoam
|
| Slush hydrogen
|
85
|
At -259 °C
|
| Solid hydrogen
|
86
|
At <−259.14 °C
|
| Liquid helium
|
147
|
At 4 K
|
| Cork
|
240
|
Average type of cork
|
| Pine
|
373
|
|
| Asbestos fibers
|
400
|
|
| Liquid methane
|
422.62
|
At 111.5 K
|
| Lithium
|
535
|
|
| Corn starch (loosely packed)
|
540
|
Negligible moisture
|
| Corn starch (tightly packed)
|
630
|
Negligible moisture
|
| Ammonia (liquid)
|
681.9
|
At boiling point
|
| Wood
|
700
|
Seasoned, typical
|
| Oak
|
710
|
|
| Aluminium silicate
|
721
|
|
| RP-1
|
773
|
At 25°C
|
| Lithium hydride
|
780
|
[1]
|
| Unsymmetrical dimethylhydrazine
|
783
|
At 25°C
|
| Isopropanol
|
786
|
Anhydrous, at 20 °C
|
| Ethanol
|
789
|
Anhydrous, at 20 °C
|
| Acetone
|
790
|
|
| Methanol
|
791.5
|
Anhydrous, at 20 °C
|
| Diesel
|
800
|
At standard conditions
|
| Gasoline
|
803
|
Average type, standard conditions
|
| Nitrogen (liquid)
|
808
|
At boiling point
|
| Kerosene
|
810
|
At standard conditions, standard composition
|
| Formaldehyde
|
815.3
|
At −20 °C
|
| Lithium-6 deuteride
|
820
|
|
| UH25
|
829
|
At 25°C
|
| α-Pinene
|
858
|
At 20 °C
|
| Potassium
|
860
|
|
| NaK (eutectic)
|
866
|
At 20°C; 77% K and 23% Na
|
| Benzene
|
870
|
At standard conditions
|
| Monomethylhydrazine
|
874
|
At 20°C
|
| Hexamethylene triperoxide diamine
|
880
|
|
| Ethylene oxide
|
882.6
|
At 10°C
|
| Aerozine 50
|
900
|
At 25°C
|
| Mayonnaise (traditional)
|
910
|
Traditional recipe
|
| Butter
|
911
|
|
| Peanut oil
|
914
|
|
| Palm oil
|
915
|
|
| Lithium aluminium hydride
|
917
|
|
| Ice
|
916.7
|
At 0 °C
|
| Olive oil
|
918
|
|
| Body fat
|
918
|
|
| Lard
|
919
|
|
| Corn oil
|
922
|
|
| Coconut oil
|
924
|
|
| Soya oil
|
927
|
|
| Nitrous oxide (liquid)
|
931
|
At 0 °C at 31.1 bar
|
| Sodium
|
970
|
|
| Silicone
|
993
|
|
| Milk (cow, heavy cream)
|
994
|
|
| Mayonnaise (light)
|
1,000
|
|
| Water
|
1,000
|
At 4 °C
|
| Saline water
|
1,004
|
(0.9% NaCl)
|
| Pilsner (beer)
|
1,008
|
At standard conditions
|
| Hydrazine
|
1,008.5
|
At 20 °C
|
| Milk (cow, light cream)
|
1,012
|
|
| Sea water
|
1,025
|
Average density at the surface
|
| Naphthalene
|
1,025.3
|
At 20 °C
|
| Milk (cow, whole)
|
1,030
|
At 20 °C
|
| Milk (cow, skim)
|
1,033
|
|
| Blood
|
1,035
|
|
| Acetic acid
|
1,050
|
|
| Skin
|
1,050
|
|
| Human body (average)
|
1,062
|
|
| Formalin
|
1,090
|
37% aqueous solution, at 25 °C
|
| Borax
|
1,121
|
|
| Nylon
|
1,150
|
|
| Oxygen (liquid)
|
1,155
|
|
| 2-Nitrotoluene
|
1,161.1
|
At 19°C
|
| Ammonium acetate
|
1,170
|
At 20 °C
|
| Plastics
|
1,175
|
Approx. for PP, PETE and PVC
|
| Methanediol
|
1,199
|
|
| Neon (liquid)
|
1,207
|
At boiling point
|
| Acetone peroxide
|
1,220
|
Trimer[2]
|
| Nitrogen (gas)
|
1,251
|
At 0 °C and 101.325 kPa)
|
| Glycerol
|
1,261
|
Standard conditions
|
| Aluminium chloride (hexahydrate)
|
1,300
|
|
| Freon 12 (liquid)
|
1,311
|
Pressurized
|
| Urea
|
1,320
|
|
| Hydrazine sulfate
|
1,378
|
[3]
|
| Corn syrup
|
1,380
|
|
| Argon (liquid)
|
1,395.4
|
At boiling point
|
| Pentaerythritol
|
1,396
|
|
| Acetylsalicylic acid
|
1,400
|
|
| Chlorobutanol
|
1,404
|
|
| Honey
|
1,420
|
|
| Boric acid
|
1,435
|
|
| Dinitrogen tetroxide
|
1,445
|
At 20 °C
|
| Hydrogen peroxide
|
1,450
|
Pure, at 20 °C
|
| Erythritol
|
1,450
|
|
| Rubidium (liquid)
|
1,460
|
At melting point
|
| Sodium sulfate (decahydrate)
|
1,464
|
|
| Sodium metabisulfite
|
1,480
|
|
| Fuming nitric acid
|
1,500
|
|
| Fluorine (liquid)
|
1,505
|
At boiling point
|
| Calcium acetate
|
1,509
|
|
| Xylitol
|
1,520
|
|
| Rubidium
|
1,532
|
At room temperature
|
| Citric acid (monohydrate)
|
1,542
|
At 18 °C
|
| Sucrose
|
1,550
|
|
| Calcium
|
1,550
|
|
| Chlorine (liquid)
|
1,562.5
|
At boiling point
|
| Ammonium bicarbonate
|
1,586
|
|
| Aluminium sulfate (octahydrate)
|
1,620
|
|
| Monosodium glutamate
|
1,620
|
At 20 °C
|
| Tetrachloroethylene
|
1,622
|
Standard conditions
|
| Ascorbic acid
|
1,650
|
|
| Oxalic acid (dihydrate)
|
1,653
|
|
| Citric acid (anhydrous)
|
1,665
|
|
| Carbonic acid
|
1,668
|
|
| Calcium gluconate (pentahydrate)
|
1,674
|
[4]
|
| Chromium(III) sulfate (octadecahydrate)
|
1,709
|
|
| Calcium chloride (hexahydrate)
|
1,710
|
|
| Aluminium nitrate (nonahydrate)
|
1,720
|
|
| Ammonium nitrate
|
1,725
|
At 20 °C
|
| Magnesium
|
1,740
|
|
| Picric acid
|
1,763
|
|
| White phosphorus
|
1,823
|
|
| Sulfuric acid (98%)
|
1,830
|
|
| Calcium chloride (tetrahydrate)
|
1,830
|
|
| Cesium (liquid)
|
1,843
|
At melting point
|
| Sodium azide
|
1,846
|
At 20 °C
|
| Calcium chloride (dihydrate)
|
1,850
|
|
| Beryllium
|
1,850
|
|
| Chromium(III) sulfate (pentadecahydrate)
|
1,860
|
|
| Francium
|
1,870
|
Predicted, at room temperature
|
| Calcium nitrate (tetrahydrate)
|
1,896
|
|
| Oxalic acid (anhydrous)
|
1,900
|
|
| Bone
|
1,900
|
Average human bone
|
| 2,4-Dinitrobromobenzene
|
1,910
|
|
| Sulfur (gamma)
|
1,920
|
|
| Cesium
|
1,930
|
At room temperature
|
| Sulfur (beta)
|
1,960
|
|
| Oleum (60%)
|
2,000
|
|
| Aluminium sulfide
|
2,020
|
|
| Sulfur (alfa)
|
2,070
|
|
| Potassium nitrate
|
2,109
|
|
| Calcium chloride (anhydrous)
|
2,150
|
|
| Sodium chloride
|
2,165
|
|
| Sodium bicarbonate
|
2,200
|
|
| Calcium hydroxide
|
2,211
|
|
| Calcium carbide
|
2,220
|
|
| Borosilicate glass
|
2,230
|
Average value
|
| Calcium chloride (monohydrate)
|
2,240
|
|
| Graphite
|
2,266
|
|
| Calcium sulfate (dihydrate)
|
2,320
|
|
| Potassium chlorate
|
2,320
|
|
| Silicon
|
2,330
|
|
| Potassium metabisulfite
|
2,340
|
|
| Red phosphorus
|
2,340
|
|
| Boron
|
2,340
|
|
| Calcium hypochlorite
|
2,350
|
At 20 °C
|
| Violet phosphorus
|
2,360
|
|
| Strontium (liquid)
|
2,375
|
At melting point
|
| Phosphorus pentoxide
|
2,390
|
|
| Concrete
|
2,400
|
|
| Krypton (liquid)
|
2,413
|
At boiling point
|
| Boron trioxide (liquid)
|
2,460
|
At melting point
|
| Aluminium chloride (anhydrous)
|
2,480
|
|
| Calcium nitrate (anhydrous)
|
2,504
|
|
| Potassium perchlorate
|
2,523.9
|
|
| Boron trioxide (trigonal)
|
2,550
|
|
| Quartz
|
2,600
|
|
| Strontium
|
2,640
|
At room temperature
|
| Calcium perchlorate
|
2,651
|
|
| Sodium sulfate (anhydrous)
|
2,664
|
|
| Aluminium sulfate (anhydrous)
|
2,672
|
|
| Black phosphorus
|
2,690
|
|
| Aluminium
|
2,700
|
|
| Calcium carbonate
|
2,830
|
Calcite
|
| Scandium (liquid)
|
2,800
|
At melting point
|
| Potassium ferrate
|
2,829
|
[5]
|
| Calcium carbonate
|
2,830
|
Aragonite
|
| Chloroauric acid (tetrahydrate)
|
2,890
|
|
| Xenon (liquid)
|
2,942
|
At boiling point
|
| Calcium sulfate (anhydrous)
|
2,960
|
|
| Scandium
|
2,985
|
At room temperature
|
| Chromium(III) sulfate (anhydrous)
|
3,100
|
|
| Bromine
|
3,102.8
|
Standard conditions
|
| Boron trioxide (monoclinic)
|
3,146
|
|
| Barium chlorate
|
3,180
|
|
| Calcium fluoride
|
3,180
|
|
| Barium nitrate
|
3,240
|
|
| Diiodomethane
|
3,325
|
|
| Barium (liquid)
|
3,338
|
At melting point
|
| Calcium oxide
|
3,340
|
|
| Diamond
|
3,510
|
|
| Barium
|
3,530
|
At room temperature
|
| Chevreul's salt
|
3,570
|
[6]
|
| Caesium hydroxide
|
3,675
|
|
| Titanium dioxide
|
3,780
|
Anatase form
|
| Chloroauric acid (anhydrous)
|
3,900
|
|
| Iodoform
|
4,008
|
|
| Zinc sulfide
|
4,090
|
|
| Titanium dioxide
|
4,180
|
Brookite
|
| Titanium dioxide
|
4,230
|
Rutile form
|
| Yttrium (liquid)
|
4,240
|
At melting point
|
| Barium carbonate
|
4,286
|
|
| Carbon tetraiodide
|
4,320
|
|
| Radon (liquid)
|
4,400
|
At boiling point
|
| Yttrium
|
4,472
|
|
| Caesium iodide
|
4,510
|
|
| Titanium
|
4,540
|
|
| Tungsten hexafluoride (solid)
|
4,560
|
At −9 °C
|
| Selenium
|
4,800
|
|
| Barium manganate
|
4,850
|
|
| Barium iodide (dihydrate)
|
4,916
|
|
| Iodine
|
4,933
|
|
| Barium iodide (anhydrous)
|
5,150
|
|
| Chromium(III) oxide
|
5,220
|
|
| Germanium
|
5,323
|
|
| Radium
|
5,500
|
At room temperature
|
| Arsenic
|
5,727
|
|
| Bismuth(III) iodide
|
5,778
|
|
| Zirconium (liquid)
|
5,800
|
At melting point
|
| Gallium
|
5,910
|
At room temperature
|
| Lanthanum (liquid)
|
5,940
|
At melting point
|
| Copper(I) oxide
|
6,000
|
|
| Gallium (liquid)
|
6,095
|
At melting point
|
| Vanadium
|
6,100
|
|
| Lead(II) iodide
|
6,160
|
|
| Lanthanum
|
6,162
|
At room temperature
|
| Ytterbium (liquid)
|
6,210
|
At room temperature
|
| Tellurium
|
6,240
|
|
| Copper(II) oxide
|
6,310
|
|
| Astatine
|
6,350
|
Predicted, at room temperature
|
| Praseodymium (liquid)
|
6,500
|
At melting point
|
| Zirconium
|
6,520
|
|
| Cerium (liquid)
|
6,550
|
At melting point
|
| Antimony
|
6,690
|
|
| Cerium
|
6,770
|
At room temperature
|
| Praseodymium
|
6,770
|
At room temperature
|
| Neodymium (liquid)
|
6,890
|
At melting point
|
| Ytterbium
|
6,900
|
At room temperature
|
| Zinc
|
7,000
|
|
| Neodymium
|
7,010
|
At room temperature
|
| Indium (liquid)
|
7,020
|
At melting point
|
| Europium (liquid)
|
7,130
|
At melting point
|
| Samarium (liquid)
|
7,160
|
At melting point
|
| Chromium
|
7,200
|
|
| Promethium
|
7,260
|
At room temperature
|
| Europium
|
7,264
|
At room temperature
|
| Indium
|
7,310
|
At room temperature
|
| Tin
|
7,310
|
|
| Manganese
|
7,325
|
|
| Gadolinium (liquid)
|
7,900
|
At melting point
|
| Samarium
|
7,520
|
At room temperature
|
| Terbium (liquid)
|
7,650
|
At melting point
|
| Iron
|
7,780
|
|
| Gadolinium
|
7,900
|
At room temperature
|
| Terbium
|
8,230
|
At room temperature
|
| Holmium (liquid)
|
8,340
|
At melting point
|
| Dysprosium (liquid)
|
8,370
|
At melting point
|
| Dysprosium
|
8,540
|
At room temperature
|
| Thulium (liquid)
|
8,560
|
At melting point
|
| Niobium
|
8,570
|
|
| Brass
|
8,600
|
|
| Cadmium
|
8,650
|
|
| Holmium
|
8,790
|
At room temperature
|
| Einsteinium
|
8,840
|
At room temperature
|
| Erbium (liquid)
|
8,860
|
At melting point
|
| Bismuth trioxide
|
8,900
|
|
| Cobalt
|
8,900
|
|
| Nickel
|
8,900
|
|
| Copper
|
8,940
|
|
| Erbium
|
9,066
|
At room temperature
|
| Polonium (alpha)
|
9,196
|
|
| Lutetium (liquid)
|
9,300
|
At melting point
|
| Thulium
|
9,320
|
At room temperature
|
| Polonium (beta)
|
9,398
|
|
| Bismuth
|
9,750
|
|
| Lutetium
|
9,841
|
At room temperature
|
| Actinium
|
10,000
|
At room temperature
|
| Molybdenum
|
10,220
|
|
| Silver
|
10,500
|
|
| Technertium
|
11,000
|
|
| Thallium (liquid)
|
11,220
|
At melting point
|
| Lead
|
11,340
|
|
| Thorium
|
11,700
|
|
| Thallium
|
11,850
|
At room temperature
|
| Hafnium (liquid)
|
12,000
|
At melting point
|
| Americium
|
12,000
|
At room temperature
|
| Palladium
|
12,023
|
|
| Rhodium
|
12,410
|
|
| Ruthenium
|
12,450
|
|
| Berkelium (beta)
|
13,250
|
At room temperature
|
| Hafnium
|
13,310
|
At room temperature
|
| Curium
|
13,510
|
At room temperature
|
| Mercury
|
13,546
|
|
| Berkelium (alpha)
|
14,780
|
At room temperature
|
| Californium
|
15,100
|
At room temperature
|
| Protactinium
|
15,370
|
At room temperature
|
| Tantalum
|
16,600
|
|
| Neptunium (gamma)
|
18,000
|
At 639 °C
|
| Uranium
|
18,900
|
|
| Tungsten
|
19,250
|
|
| Gold
|
19,320
|
|
| Neptunium (beta)
|
19,360
|
At 313 °C
|
| Plutonium
|
19,840
|
|
| Neptunium (alpha)
|
20,450
|
At 282 °C
|
| Rhenium
|
21,020
|
|
| Platinum
|
21,450
|
|
| Iridium
|
22,420
|
|
| Osmium
|
22,570
|
|
| Rutherfordium
|
23,200
|
Predicted, at room temperature
|
| Copernicium
|
23,700
|
Predicted, at room temperature
|
| Roentgenium
|
28,700
|
Predicted, at room temperature
|
| Dubnium
|
29,300
|
Predicted, at room temperature
|
| Darmstadtum
|
34,800
|
Predicted, at room temperature
|
| Seaborgium
|
35,000
|
Predicted, at room temperature
|
| Bohrium
|
37,100
|
Predicted, at room temperature
|
| Meitnerium
|
37,400
|
Predicted, at room temperature
|
| Hassium
|
40,700
|
Predicted, at room temperature
|
Density of materials at different temperatures
Air
| Temperature (°C)
|
Density (kg/m3)
|
| +727
|
0.340
|
| +227
|
0.696
|
| +35
|
1.146
|
| +30
|
1.164
|
| +27
|
1.161
|
| +25
|
1.184
|
| +20
|
1.204
|
| +15
|
1.225
|
| +10
|
1.247
|
| +5
|
1.269
|
| 0
|
1.293
|
| -5
|
1.316
|
| -10
|
1.342
|
| -15
|
1.368
|
| -20
|
1.395
|
| -25
|
1.423
|
| -73
|
1.746
|
| -173
|
3.556
|
Ammonia
| Temperature (°C)
|
Density (kg/m3)
|
| +25 °C
|
1,073
|
| +20 °C
|
1,170
|
Ammonium acetate
| Temperature (°C)
|
Density (kg/m3)
|
| +15 °C
|
0.73
|
| 0 °C
|
0,769
|
| -33.34
|
0.86
|
| -33.3
|
681.9
|
| -80 °C
|
817
|
Argon
| Temperature (°C)
|
Density (kg/m3)
|
| +27
|
1.449
|
| 0
|
1.784
|
| -185
|
1,395.4
|
Carbon dioxide
| Temperature (°C)
|
Density (kg/m3)
|
| +25
|
1.799
|
| -78
|
1,562
|
Helium
| Temperature (°C)
|
Density (kg/m3)
|
| +27
|
0.164
|
| 0
|
0.1786
|
| -269
|
147
|
Hydrazine
| Temperature (°C)
|
Density (kg/m3)
|
| +50
|
982
|
| +25
|
1,004
|
| +20
|
1,008.5
|
| +15
|
1,014
|
| 0
|
1,021
|
Hydrogen
| Temperature (°C)
|
Density (kg/m3)
|
| +125
|
0.6061
|
| +100
|
0.6465
|
| +75
|
0.6928
|
| +50
|
0.7461
|
| +25
|
0.8085
|
| 0
|
0.08988
|
| -25
|
0.9708
|
| -50
|
1.0793
|
| -75
|
1.2154
|
| -100
|
1.3911
|
| -125
|
1.6271
|
| -150
|
1.9617
|
| -175
|
2.4760
|
| -200
|
3.3817
|
| -225
|
5.5430
|
| -250
|
68.747
|
| -255
|
74.252[7]
|
Ice
| Temperature (°C)
|
Density (kg/m3)
|
| 0
|
916
|
| -50
|
922
|
| -100
|
927
|
Methane
| Temperature (°C)
|
Density (kg/m3)
|
| +25
|
0.656
|
| -90
|
162
|
Methanol
| Temperature (°C)
|
Density (kg/m3)
|
| +25
|
786.6
|
| +20
|
791.5
|
| +15
|
796
|
NaK
| Temperature (°C)
|
Density (kg/m3)
|
| +100
|
855
|
| +21
|
866
|
Naphthalene
| Temperature (°C)
|
Density (kg/m3)
|
| +100
|
962.5
|
| +20
|
1,025.3
|
| +15.5
|
1,145
|
Nitrogen
| Temperature (°C)
|
Density (kg/m3)
|
| +27
|
1.145
|
| -199
|
808
|
Oxygen
| Temperature (°C)
|
Density (kg/m3)
|
| +27
|
1.308
|
| -186
|
1,155
|
Water
| Temperature (°C)
|
Density (kg/m3)
|
| +100
|
958.4
|
| +80
|
971.8
|
| +60
|
983.2
|
| +50
|
988.03
|
| +40
|
992.2
|
| +30
|
995.6502
|
| +25
|
997.0479
|
| +22
|
997.7735
|
| +20
|
998.2071
|
| +15
|
999.1026
|
| +10
|
999.7026
|
| +4
|
999.9720
|
| 0
|
999.8395
|
| -10
|
998.117
|
| -20
|
993.547
|
| -30
|
983.854
|
The values below 0 °C refer to supercooled water.
References
- ↑ Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL)
- ↑ O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 1649
- ↑ O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. 13th Edition, Whitehouse Station, NJ: Merck and Co., Inc., 2001., p. 852
- ↑ Wieczorek; Blaszczyk; Krol; Acta Crystallographica, Section C: Crystal Structure Communications; vol. 52; nb. Pt 5;(1996); p. 1193-1198
- ↑ Hoppe, Martin L.; Schlemper, E. O.; Murmann, R. K.; Acta Crystallographica, Section B: Structural Crystallography and Crystal Chemistry; vol. 38; (1982); p. 2237 - 2239
- ↑ Etard, A.; Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences; vol. 93; (1881); p. 725 - 727
- ↑ http://hydrogen.pnl.gov/hydrogen-data/hydrogen-density-different-temperatures-and-pressures
