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3. CHEMICAL AND PHYSICAL INFORMATION
3.1 CHEMICAL IDENTITY
Information regarding the chemical identity of chromium is located in Table 3-1.
The synonyms, trade name, chemical formula, and identification numbers of chromium and selected salts
are reported in Table 3-1.
3.2 PHYSICAL AND CHEMICAL PROPERTIES
Information regarding the physical and chemical properties of chromium is located in Table 3-2.
Chromium is a metallic element with oxidation states ranging from chromium(-II) to chromium(+VI).
The important valence states of chromium are II, III, and VI. Elemental chromium, chromium(0), does
not occur naturally. The divalent state (II or chromous) is relatively unstable and is readily oxidized to
the trivalent (III or chromic) state. Chromium compounds are stable in the trivalent state and occur in
nature in this state in ores, such as ferrochromite (FeCr2O4). The hexavalent (VI or chromate) is the
second most stable state. However, hexavalent chromium rarely occurs naturally, but is produced from
anthropogenic sources (EPA 1984a). Chromium in the hexavalent state occurs naturally in the rare
mineral crocoite (PbCrO4) (Hurlburt 1971).
Trivalent chromium compounds, with the exception of acetate, hexahydrate of chloride, and nitrate salts,
are generally insoluble in water (Table 3-2). Some hexavalent compounds, such as chromium(VI) oxide
(or chromic acid), and the ammonium and alkali metal salts (e.g., sodium and potassium) of chromic acid
are readily soluble in water. The alkaline metal salts (e.g., calcium, strontium) of chromic acid are less
soluble in water. The zinc and lead salts of chromic acid are practically insoluble in cold water
(Table 3-2). The hexavalent chromium compounds are reduced to the trivalent form in the presence of
oxidizable organic matter. However, in natural waters where there is a low concentration of reducing
materials, hexavalent chromium compounds are more stable (EPA 1984a).
In humans and animals, chromium(III) is an essential nutrient that plays a role in glucose, fat, and protein
metabolism by potentiating action of insulin. Chromium picolinate, a trivalent form of chromium
complexed with picolinic acid, is used as a dietary supplement, because it is claimed to speed metabolism
CHROMIUM 260
3. CHEMICAL AND PHYSICAL INFORMATION
CH
3COO CrOOCH
3OOCH
3H
2O Cr O3NNO
3NO
3•9H
2O Cr ClCl
Cl
Table 3-1. Chemical Identity of Chromium and Compounds
Characteristic Chromium(0)
Chromium(III) acetate,
monohydrate
Chromium(III) nitrate,
nonahydrate Chromium(III) chloride
Synonym(s) Chrome; Chrom (German);
Chrome (French)
Acetic acid, chromium
salt, hydrate; chromic
acetate, hydrate
Nitric acid, chromium (III)
salt, nonahydrate;
chromium nitrate,
nonahydrate
Chromium trichloride
Registered trade name(s) Chrome No data No data C177295
Chemical formula Cr Cr(CH
3COO)3•H2O Cr(NO3)3•9H2O CrCl3Chemical structure Cr
Identification numbers:
CAS registry 7440-47-3 25013-82-5 7789-02-8 10025-73-7
NIOSH RTECS GB420000 AG3053333 GB6300000 GB5425000
EPA hazardous waste D007 No data No data No data
OHM/TADS 7216647 No data No data No data
DOT/UN/NA/IMCO
shipping
Not assigned No data No data No data
HSDB 910 No data No data No data
NCI Not assigned No data No data No data
CHROMIUM 261
2. HEALTH EFFECTS
Cr
O
P
O
O O
Table 3-1. Chemical Identity of Chromium and Compounds (
continued)Characteristic
Chromium(III) chloride
hexahydrate
Ferrochromite
(Chromium(III)) Chromium(III) oxide
Chromium(III)
phosphate
Synonym(s) Hexaaquachromium (III)
chloride
Chromite Chromium sesquioxide;
dichromium trioxide
Chromumorthophosphate;
phosphoric acid,
chromium (III) salt
Registered trade name(s) No data No data No data Amaudon’s Green
Chemical formula Cr(Cl)
3•6H20 FeCr2O4 Cr2O3 CrPO4Chemical structure Cr[Cl
2(H2O)4]Cl•2H2O FeOCr2O3 O=Cr—O—Cr=OIdentification numbers:
CAS registry 10060-12-5 1308-31-2 1308-38-9 7789-04-0
NIOSH RTECS GB5450000 GB4000000 GB6475000 GB6840000
EPA hazardous waste No data D007 D007 No data
OHM/TADS No data No data Not assigned No data
DOT/UN/NA/IMCO
shipping
No data No data Not assigned No data
HSDB No data 2963 1619 No data
NCI No data No data Not assigned No data
Table 3-1. Chemical Identity of Chromium and Compounds (
continued)CHROMIUM 262
2. HEALTH EFFECTS
NH
4O Cr O Cr ONH4O
O
O
O
Characteristic Chromium(III) sulfate
Sodium chromite
(Chromium(III)) Chromium(IV) oxide
Ammonium dichromate
(Chromium(VI))
Synonym(s) Sulfuric acid, chromium (III)
salt
No data Chromium dioxide Chromic acid, diamonium
salt
Registered trade name(s) Chromitan B No data No data No data
Chemical formula Cr
2(SO4)3 NaCrO2 CrO2 (NH4)2Cr2O7Chemical structure SO
4=Cr–SO4–Cr=SO4 NaO–Cr=O O=Cr=OIdentification numbers:
CAS registry 10101-53-8 12314-42-0 12018-01-8 7789-09-5
NIOSH RTECS GB7200000 No data GB6400000 HX7650000
EPA hazardous waste D0007 No data D007 Not assigned
OHM/TADS 7800052 No data No data 7217321
DOT/UN/NA/IMCO
shipping
Not assigned No data No data UN1439; IM05.1
HSDB 2543 No data 1620 481
NCI Not assigned No data No data No data
Table 3-1. Chemical Identity of Chromium and Compounds (
continued)CHROMIUM 263
2. HEALTH EFFECTS
Ca
O
Cr
O
O
O
Cr
O
O
O
PbO
Cr
O
O
O
KO
Cr
KO
O
O
Characteristic
Calcium chromate
(Chromium(VI)) Chromium(VI) trioxide
Lead chromate
(Chromium(VI))
Potassium chromate
(Chromium(VI))
Synonym(s) Chromic acid, calcium salt Chromic acid, chromium
anhydride
Chromic acid, lead salt Chromic acid, dipotassium
salt
Registered trade name(s) Calcium Chrome Yellow No data Chrome Yellow G No data
Chemical formula CaCrO
4 CrO3 PbCrO4 K2CrO4Chemical structure
Identification numbers:
CAS registry 13765-19-0 1333-82-0 7758-97-6 7789-00-6
NIOSH RTECS GB2750000 GB6650000 GB2975000 GB2940000
EPA hazardous waste U032; D007 D007 D007; D008 No data
OHM/TADS 7800051 Not assigned Not assigned 7217277
DOT/UN/NA/IMCO
shipping
NA9096 YB1463/UNI5.1; IM05.1 Not assigned NA9142
HSDB 248 518; NA1463 1650 1249
NCI Not assigned UN1463 Not assigned Not assigned
Table 3-1. Chemical Identity of Chromium and Compounds (
continued)CHROMIUM 264
2. HEALTH EFFECTS
Cr
O
O
KO O Cr
O
OK
O
Cr
O
O
NaO
NaO
Cr
O O
O Cr
O
O NaO NaO
•2H
2OCharacteristic
Potassium dichromate
(Chromium(VI))
Sodium chromate
(Chromium(VI))
Sodium dichromate, dihydrate
(Chromium(VI))
Synonym(s) Chromic acid, dipotassium
salt
Chromic acid, disodium
salt
Chromic acid, disodium salt; dihydrate
Registered trade name(s) No data Caswell No. 757 No data
Chemical formula K
2Cr2O7 Na2CrO4 NaCr2O7•2H20Chemical structure
Identification numbers:
CAS registry 7778-50-9 7775-11-3 7789-12-0
NIOSH RTECS HX7680000 GB2955000 HX7750000
EPA hazardous waste No data D007 No data
OHM/TADS 7217278 7216891 No data
DOT/UN/NA/IMCO
shipping
NA1479; IM09.0 No data No data
HSDB 1238 2962 No data
NCI Not assigned Not assigned No data
Table 3-1. Chemical Identity of Chromium and Compounds (
continued)CHROMIUM 265
2. HEALTH EFFECTS
Sr
O
Cr
O
O
O
Zn
O
Cr
O
O
O
N
O
O
-N
O
-ON
O
O
-Cr
+3Characteristic
Strontium chromate
(Chromium(VI))
Zinc chromate
(Chromium(VI)) Chromium(III) picolinate
Synonym(s) Chromic acid, strontium salt Chromic acid, zinc salt CrPic; Chromium 2-pyridinecarboxylate; Chromium;
tris(picolinato)-; Picolinic acid; chromium salt
Registered trade name(s) No data CI Pigment Yellow No data
Chemical formula SrCrO
4 ZnCrO4 C18H12CrN3O6Chemical structure
Identification numbers:
CAS registry 7789-06-2 13530-65-9 14639-25-9
NIOSH RTECS GB3240000 GB3290000 No data
EPA hazardous waste D007 D007 No data
OHM/TADS 780058 7217401 No data
DOT/UN/NA/IMCO NA9149 Not assigned No data
HSDB 2546 6188 No data
NCI Not assigned Not assigned No data
Source: HSDB 1998; NIOSH 1997
CAS=Chemical Abstracts Services; DOT/UN/NA/IMCO=Department of Transportation/United Nations/North America/International Maritime Dangerous Goods
Code; EPA=Environmental Protection Agency; HSDB=Hazardous Substances Data Bank; NCI=National Cancer Institute; NIOSH = National Institute for
Occupational Safety and Health; OHM/TADS=Oil and Hazardous Materials/Technical Assistance Data System; RTECS=Registry of Toxic Effects of Chemical
Substances
CHROMIUM 266
3. CHEMICAL AND PHYSICAL INFORMATION
Table 3-2. Physical and Chemical Properties of Chromium and Compounds
aProperty Chromium(0)
Chromium(III)
acetate,
monohydrate
Chromium(III)
nitrate,
nonahydrate
Chromium(III)
chloride
Molecular weight 51.996 247.15 400.15 158.36
Color Steel-gray Gray-green or
bluish-green
Purple or violet Violet or purple
Physical state Solid Solid Solid Solid
Melting point 1,857
EC No data 60 EC .1,150 ECBoiling point 2,672
EC No data Decomposes at100
ECSublimes at
1,300
ECDensity, g/cm
3 7.20 (28 EC)b No data No data 2.76 (15 EC)bOdor No data No data No data No data
Odor threshold:
Water
Air
No data
No data
No data
No data
No data
No data
No data
No data
Solubility:
Water
Organicsolvent(
s)
Insoluble
Insoluble in
common organic
solvents
Soluble
Insoluble in ethanol
Soluble
Soluble in ethanol
and acetone
Slightly soluble in
hot water
Insoluble in
common organic
solvents
Partition
coefficients:
Log K
owLog K
ocNot applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Vapor pressure 1 mmHg at
1,616
ECNo data No data No data
Henry’s law
constant
Not applicable Not applicable Not applicable Not applicable
Autoignition
temperature
No data No data No data No data
Flashpoint No data No data No data No data
Flammability limits No data No data No data No data
Conversion factors No data No data No data No data
Explosive limits No data No data No data No data
CHROMIUM 267
3. CHEMICAL AND PHYSICAL INFORMATION
Table 3-2. Physical and Chemical Properties of Chromium and
Compounds (
continued)Property
Chromium(III)
chloride,
hexahydrate
Ferrochromite
(Chromium(III))
Chromium(III)
oxide
Chromium(III)
phosphate
Molecular weight 266.45 223.84 151.99 146.97
Color Violet Brown-black Green Gray-brown to black
dPhysical state Solid Solid Solid Solid
Melting point 83
EC No data 2,266 EC >1,800 ECBoiling point No data No data 4,000
EC No dataDensity g/cm
3 1.76c 4.97 (20 EC) 5.21c 2.94 (32.5 EC)b,dOdor No data No data No data No data
Odor threshold:
Water
Air
No data
No data
No data
No data
No data
No data
No data
No data
Solubility:
Water
Organic
solvent(s)
58.5 g/100 cc at
25
ECSoluble in ethanol
Insoluble
No data
Insoluble
Insoluble in ethanol
Insoluble
dNo data in ethanol
Partition coefficients:
Log K
owLog K
ocNo data
No data
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Vapor pressure No data No data No data No data
Henry’s law constant No data Not applicable Not applicable Not applicable
Autoignition
temperature
No data No data No data No data
Flashpoint No data No data No data No data
Flammability limits No data No data No data No data
Conversion factors No data No data No data No data
Explosive limits No data No data No data No data
CHROMIUM 268
3. CHEMICAL AND PHYSICAL INFORMATION
Table 3-2. Physical and Chemical Properties of Chromium and
Compounds (
continued)Property
Chromium(III)
sulfate
Sodium chromite
(Chromium(III))
Chromium(IV)
oxide
Ammonium
dichromate
(Chromium(VI))
Molecular weight 392.16 106.98 83.99 252.06
Color Violet or red No data Brown-black Orange
Physical state Solid No data Solid Solid
Melting point No data No data Decomposes at
300
ECDecomposes at
170
ECBoiling point No data No data Not applicable Not applicable
Density g/cm
3 3.012c No data No data 2.15 (25 EC)bOdor No data No data No data No data
Odor threshold:
Water
Air
No data
No data
No data
No data
No data
No data
No data
No data
Solubility:
Water
Organic
solvent(s)
Insoluble
Slightly soluble in
ethanol
No data
No data
Insoluble
No data
30.8 g/100 cc
at 15
ECSoluble in ethanol
Partition
coefficients:
Log K
owLog K
ocNot applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Vapor pressure No data No data No data No data
Henry’s law
constant
Not applicable Not applicable Not applicable Not applicable
Autoignition
temperature
No data No data No data No data
Flashpoint No data No data No data No data
Flammability limits No data No data No data No data
Conversion factors No data No data No data No data
Explosive limits No data No data No data No data
CHROMIUM 269
3. CHEMICAL AND PHYSICAL INFORMATION
Table 3-2. Physical and Chemical Properties of Chromium and
Compounds (
continued)Property
Calcium chromate
(ChromiumVI)
Chromium(VI)
trioxide
Lead chromate
(Chromium(VI))
Potassium
chromate
(Chromium(VI))
Molecular weight 156.01 99.99 323.18 194.20
Color Yellow Red Yellow Yellow
Physical state Solid Solid Solid Solid
Melting point No data 196
EC 844 EC 968 ECBoiling point No data Decomposes Decomposes No data
Density g/cm
3 2.89c 2.70 (25 EC) 6.12 (15 EC) 2.732 (18 EC)Odor No data No data No data No data
Odor threshold:
Water
Air
No data
No data
No data
No data
No data
No data
No data
No data
Solubility:
Water
Organic
solvent(s)
2.23 g/100 mL
cNo data
61.7 g/100 cc at
0
ECSoluble in ethanol
and ether
5.8 µg/100 mL
Insoluble in acetic
acid
62.9 g/100 at 20
ECInsoluble in ethanol
Partition
coefficients:
Log K
owLog K
ocNot applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Vapor pressure No data No data No data No data
Henry’s law
constant
Not applicable Not applicable Not applicable Not applicable
Autoignition
temperature
No data No data No data No data
Flashpoint No data No data No data No data
Flammability limits No data No data No data No data
Conversion factors No data No data No data No data
Explosive limits No data No data No data No data
CHROMIUM 270
3. CHEMICAL AND PHYSICAL INFORMATION
Table 3-2. Physical and Chemical Properties of Chromium and
Compounds (
continued)Property
Potassium dichromate
(Chromium(VI))
Sodium chromate
(Chromium(VI))
Sodium dichromate,
dihydrate
(Chromium(VI))
Molecular weight 294.18 161.97 298.00
Color Red Yellow Red
Physical state Solid Solid Solid
Melting point 398
EC 792 EC 356.7 ECBoiling point Decomposes at
500
ECNo data Decomposes at
400
ECDensity g/cm
3 2.676 (25 EC) 2.710–2.736c 2.52 (13 EC)Odor No data No data No data
Odor threshold:
Water
Air
No data
No data
No data
No data
No data
No data
Solubility:
Water
Organic solvent(s)
4.9 g/100 cc at 0
ECInsoluble in ethanol and
acetone
87.3 g/100 cc
at 30
ECSoluble in methanol
230 g/100 cc at 0
ECInsoluble in ethanol
Partition coefficients:
Log K
owLog K
ocNot applicable
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
Vapor pressure No data No data No data
Henry’s law constant Not applicable Not applicable Not applicable
Autoignition temperature No data No data No data
Flashpoint No data No data No data
Flammability limits No data No data No data
Conversion factors No data No data No data
Explosive limits No data No data No data
CHROMIUM 271
3. CHEMICAL AND PHYSICAL INFORMATION
Table 3-2. Physical and Chemical Properties of Chromium and
Compounds (
continued)Property
Strontium chromate
(Chromium(VI))
Zinc chromate
(Chromium(VI))
Chromium(III)
picolinate
Molecular weight 203.61 181.97 418.3
eColor Yellow Lemon-yellow Ruby red
ePhysical state Solid Solid Crystal
eMelting Point No data No data No data
Boiling Point No data No data No data
Density g/cm
3 3.895 (15 EC) 3.40c No dataOdor No data Odorless No data
Odor threshold:
Water
Air
No data
No data
No data
No data
No data
No data
Solubility:
Water
Organic solvent(s)
0.12 g/100 cc
at 15
ECSoluble in acetyl acetone
Insoluble
Insoluble in acetone
1 ppm at 25
ECe>6 g/L (DMSO)
ePartition coefficients:
Log K
owLog K
ocNot applicable
Not applicable
Not applicable
Not applicable
1.753
fNo data
Vapor pressure No data No data No data
Henry’s law constant Not applicable Not applicable No data
Autoignition temperature No data No data No data
Flashpoint No data No data No data
Flammability limits No data No data No data
Conversion factors No data No data No data
Explosive limits No data No data No data
a
Hartford 1979; Weast 1985, except when notedb
Temperature at which the densities were measured has been given only when such data is availablec
Temperature at which density was measured was not specifiedd
Windholz 1983e
Broadhurst et al. 1997f
Chakov et al. 1999DMSO=dimethylsulfoxide
CHROMIUM 272
3. CHEMICAL AND PHYSICAL INFORMATION
and may have anti-diabetic effects (Broadhurst et al. 1997). It has also been shown to be absorbed more
readily than chromium obtained from food sources (Gargas et al. 1994). Unfortunately, the mechanism of
transport and absorption of chromium picolinate has not been determined. Recently, a spectroscopic
analysis of this compound has shown that chromium picolinate is a very stable complex in the body and
its absorption properties may be due to its ability to cross membranes readily (Chakov et al. 1999).
CHROMIUM 273
'see also:
Sec 7 - REGULATIONS
Toxicological Profile for Chromium - Agenct for Toxic SubstancesAgenct for Toxic Substances: Toxicological Profile for Chromium
Sec 1 - Public Health Statement
Toxicological Profile for Chromium - Agenct for Toxic SubstancesAgenct for Toxic Substances: Toxicological Profile for Chromium
Complete Toxicological Profile for Chromium
Toxicological Profile for Chromium - Agenct for Toxic SubstancesAgenct for Toxic Substances: Toxicological Profile for Chromium
