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IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Chromium, Nickel and also Welding. Lyon (FR): Internationwide Agency for Research on Cancer; 1990. (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 49.)
Chromium and also chromium compounds were thought about by previous IARC Working Groups, in 1972, 1979, 1982 and 1987 (IARC, 1973, 1979, 1980a, 1982, 1987a). Since that time, new information have become easily accessible, and these are included in the current monograph and have actually been taken right into consideration in the evaluation.
1. Chemical and also Physical Data
The list of chromium alloys and compounds offered in Table 1 is not exhaustive, nor does it necessarily reflect the commercial importance of the assorted chromium-containing substances, however it is indicative of the range of chromium alloys and also compounds obtainable.
Synonyms (Chemical Abstracts Service names are given in bold), profession names and also atomic or molecular formulae of chromium and also schosen chromium compounds.
1.1. Synonyms, profession names and molecular formulae of chromium and also selected chromium-containing compounds
1.2. Chemical and physical properties of pure substances
Known physical properties of some of the chromium compounds taken into consideration in this monograph are provided in Table 2. Data on solubility refer to saturated solutions in water or other mentioned solvents. Hexavalent chromium compounds are customarily classed as soluble or insoluble in water; such a classification is valuable in market yet could not be relevant to determining the biological properties of a compound. Tbelow is for this reason no basic agreement on the definition of solubility: in practice, the aqueous solubility of Cr
Physical properties of chromium and chromium compounds.
(a) Chromite ore
Chromite ore consists of varying percenteras of chromium, iron, aluminium and magnesium oxides as the major components. It has been classified into 3 general grades linked through their use and chromic oxide content: metallurgical (greater than 46%), chemical (40–46%) and also refractory (much less than 40%) grades (Papp, 1985). Throughout the previous two decades, technological breakthroughs have actually enabled significant interchangecapability among the various grades, particularly the so-referred to as chemical grade which have the right to be made use of in all 3 sectors. An even more definitive classification is: (i) ‘high-chromium’ chromite (metallurgical-grade), containing a minimum of 46% chromic oxide and a chromium:iron proportion higher than 2:1; (ii) ‘high-iron’ chromite (chemical-grade), with 40–46% chromic oxide and also a chromium:iron proportion of 1.5:1 to 2:1; and (iii) ‘high-aluminium’ chromite (refractory-grade), containing even more than 20% aluminium oxide and also more than 60% aluminium oxide plus chromic oxide (Papplication, 1983).
Chromite from one US processor had the following typical analysis: chromium (as chromic oxide), 45.57%; iron (as ferric oxide), 29.80%; aluminium (as aluminium oxide), 13.80%; magnesium (as magnesium oxide), 9.28%; silicon (as silicon dioxide), 1.13%; and calcium (as calcium oxide), 0.40% (Cyprus Specialty Metals, 1988).
(b) Metallic chromium and chromium alloys
Chromium (pure) metal is a minor product of the metallurgical processing of chromium. It is obtainable as electrolytic chromium (98.7–99.5% Cr; Elkem Metals Co., 1986), aluminothermic chromium (98.3% Cr (Morning, 1975) and also 99.0–99.8% Cr (Delachaux, 1989)) and vacuum aluminothermic chromium (99.5–99.8% Cr; Delachaux, 1989). Electrolytic chromium and aluminothermic chromium typically contain traces of silicon, carbon, phosphorus, sulfur, iron, aluminium, nitrogen, oxygen and also hydrogen (Elkem Metals Co., 1986; Belmont Metals, 1989). Chromium metal quickly forms an oxide layer at the surface in air; such oxidation of carefully separated chromium powder deserve to bring about the convariation of a large fraction of the metal to steel oxide upon expanded storage (Sunderguy et al., 1974).
Ferrochromiums are the main intermediates in the metallurgical processing of chromium. There are three categories: high-carbon, low-carbon and also ferrochromium silicon. The compositions of typical ferrochromiums are provided in Table 3 (Morning, 1975).
Composition of typical ferrochromium and chromium steels.
Chromium-containing steels are usually stainmuch less steels and are iron-base alloys. Some representative analyses of miscellaneous grades are offered in Table 4.
Elemental analysis of representative qualities of stainmuch less steel.
Chromium alloys have the right to be categorized as nickel-chromium, cobalt-chromium and iron-nickel-chromium alloys. Some representative analyses are provided in Table 5.
Elemental analyses of representative chromium alloys (weight %).
An array of chromium-containing alloys is offered for surgical implants. Specifications of the Amerihave the right to Society for Testing and Materials for such alloys are provided in Table 6.
Complace specifications for 4 representative chromium-containing alloys offered in surgical implants (weight %).
Basic chromic sulfate is created by one company in the UK, as 67% basic chromic sulfate and also 25–37% sodium sulfate (British Chrome & Chemical Ltd, 1988).
Chromic acetate is accessible as a 50% green aqueous solution via the complying with typical analysis; chromium, 11.4%; sulfate, less than 0.2%; chloride, less than 0.1% (McGean-Rohco, 1984).
Chromic chloride hexahydrate is accessible as a 62% green aqueous solution, generally containing 12% chromium and also less than 0.2% sulfate (McGean-Rohco, 1984).
Chromic nitprice is easily accessible as a hydrate (Cr(NO3)3.7.5-9H2O) in granules; 12.5–13.5% chromium and also as the nonahydrate in liquid develop (6.5–10.9% chromium) (McGean-Rohco, 1984).
Chromic oxide is obtainable in several grades relying on its use in metallurgical and refractory sectors. A typical analysis of a metallurgical grade is 99.4% chromium (as chromic oxide) and less than 0.1% moisture. A typical evaluation of a refractory grade is 98.5–99.4% chromium (as chromic oxide), 0.1% alkali steels (as sodium oxide), 0.1% other metal oxides (mostly aluminium, iron and also magnesium), and average pwrite-up size, 0.5–3.5 μm (Amerihave the right to Chrome & Chemicals, undated a,b,c,d). Chromic oxide pigment (dark chromium oxide) commonly includes > 99.0% chromium as chromic oxide (Mineral Pigments Corp., undated a).
Chrome base spinels are part of the household of combined metal oxide organic coloured pigments. Two such pigments are (i) chromium iron nickel babsence spinel, the composition of which might include any type of one or a mix of cupric oxide, manganese oxide and manganese sesquioxide as modifiers, and (ii) chrome manganese zinc brvery own spinel, which may contain any one or a mix of aluminium oxide, nickel monoxide, silicon dioxide, stannous oxide and also titanium dioxide as modifiers (Dry Color Manufacturers" Association, 1982).
Chromic phosphate tetrahydprice is available with a purity of 99.9% (National Chemical Co., undated a).
Analytical reagent-grade chromium sulfate hydprice is accessible with the adhering to impurities: ammonium, 0.01% max; chloride, 0.002% max; insoluble issue, 0.01% max; and iron, 0.01% max. Analytical reagent-grade potassium chromic sulfate dodecahydprice is accessible at a purity higher than 98.0%. Potassium chromic sulfate with assorted degrees of hydration is available commercially as Chrome Alum Crystal (violet crystals) containing 10% chromium and also Chrome Alum 0% Basicity (green powder) containing 15.4% chromium (McGean-Rohco, 1984).
Ammonium dichromate is easily accessible as analytical reagent-grade crystals (99.5%) and also as purified-grade crystals and granules with the adhering to impurities: chloride, 0.005% max; addressed alkalis (as sulfate), 0.1–0.2% max; insoluble matter, 0.005% max; and also sulfate, 0.005% max.
Calcium chromate is obtainable at a purity of 96% min (Barium & Chemicals, 1988a). When supplied as a pigment for primer applications, it has the following typical analysis: chromium oxide, 45%; calcium oxide, 44%; chloride, less than 0.001%; sulfate, much less than 0.001%; and moisture, 0.01% (National Chemical Co., undated b).
Chromium trioxide is available commercially at a purity of 99.9% (McGean-Rohco, 1984; Occidental Chemical Corp., 1987a; American Chrome & Chemicals, undated e). Two grades easily accessible from one firm in Europe contain maxima of 20 and 100 mg/kg metallic impurities.
Analytical reagent-grade potassium chromate (crystals) is obtainable at a purity of 99.0%. Potassium dichromate is easily accessible at a purity of 99.8% (Occidental Chemical Corp., 1987b).
Technical-grade anhydrous sodium chromate is easily accessible at a purity of 99.5% (Occidental Chemical Corp., 1987c). Sodium dichromate dihydprice is obtainable at a purity of 100.0% (Amerideserve to Chrome & Chemicals, undated f). Anhydrous sodium dichromate is accessible at a purity of 99.70% (Amerideserve to Chrome & Chemicals, undated g).
Barium chromate is accessible at a purity of 98.5–99% (Atomergic Chesteels Corp., 1980; Barium & Chemicals, 1988b; National Chemical Co., undated c).
The term ‘zinc chromate’ is a generic term for a series of commercial commodities through 3 kinds of molecular structure: (i) ‘zinc chromate’ form (prefer ZnCrO4); (ii) ‘basic zinc chromate’ form (favor zinc tetrahydroxychromate (ZnCrO4.4Zn(OH)2); and also (iii) ‘(basic) zinc potassium chromate’ form (like 3ZnCrO4.Zn(OH)2.K2CrO4. 2H2O). Several various commercial ‘zinc chromates’ are additionally described as ‘zinc yellow’.
Analytical reagent-grade lead chromate powder is available at a purity of > 98%. The commercial lead chromate pigments, Primclimbed Chrome Yellow, Light Chrome Yellow and Medium Chrome Yellow, contain 65–89% lead chromate (Mineral Pigments Corp., undated b,c; National Chemical Co., undated d).
Molybdenum ovariety is defined as a facility of lead molybday, lead chromate and lead sulfate (National Chemical Co., undated e). One complace comprises 65% lead, 12% chromium and also 3% molybdenum (Wayne Pigment Corp., 1985a,b).
Strontium chromate is available at a purity of 99% (National Chemical Co., undated f). A strontium chromate pigment is obtainable with a typical analysis of 41.4% strontium and also 46.7–47.3% chromium (Mineral Pigments Corp., undated d).
(a) Chromite ore
Although chromium is uncovered in assorted minerals, chromite is the single source of chromium used commercially (Stern, 1982). From 1797 till 1827, chromite from the Ural Mountains of Russia was the principal resource of human being supply, primarily for chemical usage. After chromite ore was discovered in the USA in 1827, that country came to be the major source for the restricted people demand; it no longer produces it. Large Turkish deposits were developed in 1860 to supply the people industry. Table 7 presents civilization production numbers by region in 1976, 1982 and also 1987.
(b) Metallic chromium and chromium alloys
Chromium metal is made commercially in the USA by 2 processes: (i) an electrolytic technique in which a chromium-containing electrolyte, ready by disresolving a high-carbon ferrochromium in a solution of sulfuric acid and also chromium potassium sulfate, is based on electrolysis; and (ii) an aluminothermic reduction approach in which chromic oxide is reduced through finely divided aluminium (Bacon, 1964; Papplication, 1983).
In 1970, US production of chromium steel and metal alloys, various other than ferrochromium alloys, was 14 thousand also tonnes (around 75% by the electrolytic method; IARC, 1980a); this had increased to 18 thousand tonnes by 1976 (Morning, 1978). Production included chromium briquets, exothermic chromium additives and also miscellaneous chromium alloys, in addition to chromium metal. By 1987, US manufacturing of chromium steel and also ferrochromium-silicon (consisting of exothermic chromium additives and also various other assorted chromium alloys) had dropped to 1900 tonnes (Papplication, 1988).
Chromium metal has actually been produced in Japan since 1956, where it is manufactured by two carriers by electrolysis of an ammonium chromic sulfate solution. About 9000 tonnes were developed in 1977; there were no reported imports or exports (IARC, 1980a).
Ferrochromium is developed by treatment of chromite ore in electrical heating systems making use of coke as a reducing agent. Worldwide manufacturing figures for all qualities of ferrochromium are summarized in Table 8.
Chromium-containing steels (stainless steels and also others) are produced by melting cast iron and also adding ferrochromium and/or steel scraps in huge electric furnaces. The melt is transferred to a refining vessel to change the carbon content and impurity levels and is then actors right into ingots or repetitively into casting forms. Defects in the actors steel are repaired by cutting or scarfing or by chipping or grinding. The desired forms are developed generally by rolling, and also their surfaces are conditioned by a selection of operations, consisting of grinding, sprucing up and pickling (Warner, 1984).
Production figures are offered in Table 9.
Chromium alloys are created by innovation exceptionally equivalent to that used for steel manufacturing, except that the melting and decarburizing systems are generally smaller and higher use is made of vacuum melting and remelting (Warner, 1984). No data were available on manufacturing volumes of these alloys.
Cobalt-chromium alloys were first made in 1907 by fusion of cobalt with 10–60% chromium (Haynes, 1907). Commercial manufacturing began quickly thereafter, and also since 1920 more than 75% of the cobalt provided in the USA has been for the manufacture of alloys through chromium (Sibley, 1976).
Eight US service providers created chromium alloys in 1975, however separate information on the quantity of cobalt-chromium alloys created were not available (Morning, 1978). Stellite (normally 53% Co, 35% Cr and the remainder tungsten) has been developed by one firm in the UK (Roskill Information Services, 1974).
Solutions of chromic acetate are developed by dissolving freshly prepared hydrous chromic oxide in acetic acid (IARC, 1980a). Commercial mixtures of chromic acetate with sodium acetate have actually been ready by reduction of sodium dichromate with glucose or corn sugar in the existence of acetic acid (Copchild, 1956).
Chromic acetate was created by five carriers in the USA, yet no data on volumes were available (IARC, 1980a); it is now produced by one agency (Chemical Information Services Ltd, 1988). Annual production in Japan has actually been around 30 tonnes (IARC, 1980a). Chromic acetate is presently developed by 2 service providers each in Japan and the UK and one each in Australia, Canada and also Italy (Chemical Information Services Ltd, 1988).
Chromic chloride hexahydprice is prepared by dissolving freshly all set chromium hydroxide in hydrochloric acid. Anhydrous chromic chloride deserve to be developed by passing chlorine over a mixture of chromic oxide and carbon (Sax & Lewis, 1987). Chromic chloride has been created by two providers in the USA, however no data on volumes were accessible.
In Japan, chromic chloride has been developed from chromic sulfate by converting it to purified chromic carbonate, which is treated with hydrochloric acid. About 100 tonnes of chromic chloride were produced by one Japanese company in 1977; there were no reported imports or exports. Four service providers presently develop chromic chloride in Japan (Chemical Information Services Ltd, 1988).
Chromic chloride is additionally created by 3 companies in the UK, 2 in the Federal Republic of Germany and one each in Australia and also the Germale Democratic Republic (Chemical Information Services Ltd, 1988).
Chromic hydroxide is produced by adding a solution of ammonium hydroxide to the solution of a chromium salt (Sax & Lewis, 1987). It is developed by one firm each in Argentina, Brazil, France, Japan and Turessential, 2 each in Austria, Spain, the UK and also the USA and also 4 in India (Chemical Information Services Ltd, 1988).
Chromic nitprice may be developed by the action of nitric acid on chromium hydroxide (Sax & Lewis, 1987). It is produced by 3 companies each in Japan, the UK and the USA, two each in Italy and also Spain and also one in the Federal Republic of Germany type of (Chemical Indevelopment Services Ltd, 1988).
Anhydrous chromic oxide is developed commercially by heating chromic hydroxide, by heating dry ammonium dichromate, or by heating sodium dichromate via sulfur and washing out the sodium sulfate (Sax & Lewis, 1987). The hydrated product is made commercially by calcining sodium dichromate via boric acid and hydrolysing chromic boprice (IARC, 1980a).
Chromic oxide was produced by 6 carriers in the USA in 1977. US production of the a lot of crucial form of chromic oxide, chromic oxide green, was reported to be about 6000 tonnes in 1971 (IARC, 1980a), about 3700 tonnes in 1976 and 2700 tonnes in 1977 (Hartford, 1979). It is now developed by one company in the USA (Chemical Indevelopment Services Ltd, 1988). Chromic oxide has been produced in Japan by two service providers, either by heating hydrous chromic oxide or chromium trioxide or by reducing sodium dichromate via carbon. An estimated 2700 tonnes were developed in 1977 (IARC, 1980a). It is likewise developed by 2 suppliers each in the Federal Republic of Germany type of and also the UK and one each in France, India, Italy, Spain and also Switzerland also (Chemical Indevelopment Services Ltd, 1988).
A violet hexahydprice create of chromic phosphate is created by mixing cold solutions of potassium chromium sulfate (chrome alum) with disodium phosphate. A green crystalline dihydprice is derived by boiling the violet hexahydrate via acetic anhydride or by heating it in dry air (Udy, 1956).
Chromic phosphate is developed by two companies in the USA and also one each in Australia, Austria, the Federal Republic of Germany type of, India, Japan and the UK (Chemical Indevelopment Services Ltd, 1988).
Solutions of mixed hydrated chromic sulfates are obtained by disaddressing chromic oxide in focused sulfuric acid and allowing it to stand till crystals of the hydrated chromic sulfate separate. The anhydrous create is developed by heating any kind of of the hydprices to 400°C in air or to 280°C in a stream of carbon dioxide (IARC, 1980a). Mixtures of fundamental chromic sulfates (containing mostly Cr(OH)SO4) with sodium sulfate are developed commercially by the organic reduction (with such substances as molasses) of a solution of sodium dichromate in the visibility of sulfuric acid or by reduction of dichromate remedies through sulfur dioxide (Copkid, 1956).
Two suppliers in the USA create chromium sulfate and one produces basic chromic sulfate, yet no data on volumes were accessible (Chemical Information Services Ltd, 1988).
Both chromium sulfate and fundamental chromic sulfate have actually been produced in Japan considering that about 1950, by reduction of sodium dichromate via glucose. The linked manufacturing of the two producers in 1977 (which are still operating) was about 2000 tonnes fundamental chromic sulfate and also about 120 tonnes chromium sulfate (IARC, 1980a).
Chromium sulfate is likewise produced by one company each in Brazil, France, India and also New Zealand, two each in the Federal Republic of Germany and also Spain and three in the UK. Basic chromic sulfate is also developed by one firm each in Australia, Brazil, Colombia, Italy, Mexico, Pakistan, Turessential and the USSR, two each in China and also India and 3 in the UK (Chemical Information Services Ltd, 1988).
Potassium chromic sulfate dodecahydprice (potassium chrome alum) is created commercially by the reduction of potassium dichromate via sulfur dioxide (Copchild, 1956). One agency in the USA presently produces potassium chromic sulfate, yet no information on quantities were available (Chemical Information Services Ltd, 1988). It was created commercially in Japan before 1940. Production reached around 20–30 tonnes in 1970; subsequently, the annual quantity produced reduced quickly, and only about one tonne was developed in 1977 (IARC, 1980a).
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Potassium chromic sulfate is likewise developed by one firm in Brazil and one firm in Czechoslovakia (Chemical Indevelopment Services Ltd, 1988).