ACGIH: TWA 0.0002 mg/m3; STEL 0.0005 mg/m3 (Skin)OSHA: Ceiling 0.1 mg/m3NIOSH: IDLH 15 mg/m3; TWA 0.0002 mg/m3
物理描述:
Calcium chromate is a yellow powder. It is slightly soluble in water. The primary hazard is the threat to the environment. Immediate steps should be taken to prevent its spread to the environment.
IDENTIFICATION AND USE: Calcium chromate (CaCrO4) is a bright yellow powder. It is used as a pigment, corrosion inhibitor, oxidizing agent, depolarizer for batteries, and coating for light metal alloys. HUMAN EXPOSURE AND TOXICITY: Calcium chromate is a suspected human carcinogen. It has been reported that eliminating the formation of calcium chromate, had resulted in a distinct reduction in bronchial carcinoma mortality among workers at chromate-producing factories exposed for the first time after the change-over. In vitro, human cells exhibited four times more DNA breaks than the hamster cells and two times more than mouse embryo fibroblast cells when the CaCrO4 exposure conditions were equivalent. Alkaline elution studies also demonstrated the formation of DNA-protein cross-links by CaCrO4 in all three cell lines. The level of cross-links was four times greater in the human cells compared to the mouse cells and was a factor of 2 greater in the hamster cells compared to the mouse cells. In other in vitro experiment, treatments with various concentrations of K2Cr2O7, CaCrO4, and CrO3 were given to human lymphocytes cultured in presence of BrdUrd for 2 replicative cycles. Sister-chromatid exchanges (SCEs) were visualized. In all cases, the higher the concentrations the higher the frequencies of SCEs per metaphase and per chromosome. On a concentration basis, the order of effectiveness in producing SCEs was: CaCrO4 much greater than CrO3 greater than K2Cr2O7. ANIMAL STUDIES: Calcium chromate produced bronchial carcinomas after implantation of an intrabronchial pellet in rats and injection-site sarcomas after intramuscular implantation in rats and mice and after intrapleural injection in rats. Calcium chromate was positive for the induction of sex linked recessive mutations in Drosophila melanogaster at dietary levels of 500 and 700 ppm. Calcium chromate was positive in the L5178Y TK+/TK- mouse lymphoma forward mutation assay. Chromosomal aberrations were studied in Chinese hamster ovary cells and in C3H10T1/2 cells following treatment with NiCl2, crystalline NiS, and CaCrO4. All three compounds caused an increase in chromosomal aberrations in a concentration- and time-dependent fashion. Alkaline elution studies demonstrated CaCrO4-induced DNA single strand breaks and DNA-protein crosslinks in Chinese hamster ovary cells. ECOTOXICITY STUDIES: Calcium chromate at 200 ppm inhibited plant growth by 50%.
WEIGHT OF EVIDENCE CHARACTERIZATION: Under the current guidelines (1986), Cr(VI) is classified as Group A - known human carcinogen by the inhalation route of exposure. Carcinogenicity by the oral route of exposure cannot be determined and is classified as Group D. Under the proposed guidelines (1996), Cr(VI) would be characterized as a known human carcinogen by the inhalation route of exposure on the following basis. Hexavalent chromium is known to be carcinogenic in humans by the inhalation route of exposure. Results of occupational epidemiological studies of chromium-exposed workers are consistent across investigators and study populations. Dose-response relationships have been established for chromium exposure and lung cancer. Chromium-exposed workers are exposed to both Cr(III) and Cr(VI) compounds. Because only Cr(VI) has been found to be carcinogenic in animal studies, however, it was concluded that only Cr(VI) should be classified as a human carcinogen. Animal data are consistent with the human carcinogenicity data on hexavalent chromium. Hexavalent chromium compounds are carcinogenic in animal bioassays, producing the following tumor types: intramuscular injection site tumors in rats and mice, intrapleural implant site tumors for various Cr(VI) compounds in rats, intrabronchial implantation site tumors for various Cr(VI) compounds in rats and subcutaneous injection site sarcomas in rats. In vitro data are suggestive of a potential mode of action for hexavalent chromium carcinogenesis. Hexavalent chromium carcinogenesis may result from the formation of mutagenic oxidatitive DNA lesions following intracellular reduction to the trivalent form. Cr(VI) readily passes through cell membranes and is rapidly reduced intracellularly to generate reactive Cr(V) and Cr(IV) intermediates and reactive oxygen species. A number of potentially mutagenic DNA lesions are formed during the reduction of Cr(VI). Hexavalent chromium is mutagenic in bacterial assays, yeasts and V79 cells, and Cr(VI) compounds decrease the fidelity of DNA synthesis in vitro and produce unscheduled DNA synthesis as a consequence of DNA damage. Chromate has been shown to transform both primary cells and cell lines. HUMAN CARCINOGENICITY DATA: Occupational exposure to chromium compounds has been studied in the chromate production, chromeplating and chrome pigment, ferrochromium production, gold mining, leather tanning and chrome alloy production industries. Workers in the chromate industry are exposed to both trivalent and hexavalent compounds of chromium. Epidemiological studies of chromate production plants in Japan, Great Britain, West Germany, and the United States have revealed a correlation between occupational exposure to chromium and lung cancer, but the specific form of chromium responsible for the induction of cancer was not identified ... Studies of chrome pigment workers have consistently demonstrated an association between occupational chromium exposure (primarily Cr(VI)) and lung cancer. Several studies of the chromeplating industry have demonstrated a positive relationship between cancer and exposure to chromium compounds. ANIMAL CARCINOGENICITY DATA: Animal data are consistent with the findings of human epidemiological studies of hexavalent chromium ... /Chromium (VI)/
Evaluation: There is sufficient evidence in humans for the carcinogenicity of chromium(VI) compounds. Chromium(VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium(IV) compounds and cancer of the nose and nasal sinuses. There is sufficient evidence in experimental animals for the carcinogenicity of chromium(VI) compounds. Chromium(VI) compounds are carcinogenic to humans (Group 1). /Chromium(VI) compounds/
Expansion of the photoresponse window of a BiVO<sub>4</sub> photocatalyst by doping with chromium(<scp>vi</scp>)
作者:Kazuya Okuno、Hideki Kato、Junie Jhon M. Vequizo、Akira Yamakata、Hisayoshi Kobayashi、Makoto Kobayashi、Masato Kakihana
DOI:10.1039/c8ra07830k
日期:——
Photocatalytic O2 evolution is induced by electrons/holes generated by excitation of a new absorption band formed by doping with Cr6+.
使用Cr6+掺杂形成的新吸收带激发产生的电子/空穴诱导了光催化O2的产生。
Formation, thermal redox reaction and crystal structure of δ-CaCr2O4
作者:Jaegyeom Kim、Jinho Shin、Seung-Min Paek、Dae Sung Park、Seung-Joo Kim
DOI:10.1016/j.jssc.2021.122669
日期:2022.1
The thermal redox reactions of a Ca–Cr–O system under different atmospheric conditions were investigated by cyclic thermodiffractometry and thermogravimetry. In the first heating process under a reductive atmosphere, CaCrO4 decomposed into CaO and δ-CaCr2O4, a metastable form, with the liberation of free oxygen. In the second process under an oxidizing atmosphere, the CaO and δ-CaCr2O4 produced in
通过循环热衍射法和热重法研究了 Ca-Cr-O 体系在不同大气条件下的热氧化还原反应。在还原气氛下的第一次加热过程中,CaCrO 4分解为CaO和δ-CaCr 2 O 4,一种亚稳态形式,释放出游离氧。在氧化气氛下的第二个过程中,第一次还原过程中产生的CaO和δ-CaCr 2 O 4反应生成CaCrO 4,表明该氧化还原反应可以通过控制气氛可逆地进行。δ-CaCr 2 O 4的晶体结构首次根据高分辨率同步加速器粉末 X 射线衍射数据确定。δ-CaCr 2 O 4以单斜晶结构结晶,空间群为P 2 1 / m。该结构可以描述为由共享边缘的 CrO 6八面体组成的 CrO 2层的堆叠,钙离子就地驻留在层之间。钙离子由六个氧原子配位以在 CrO 2层之间形成三棱柱几何结构。δ-CaCr 2 O 4结构与低温β-CaCr 2 O 4 结构不同(扭曲的CaFe 2 O 4型)和高温α-CaCr 2 O
Molten calcium nitrate tetrahydrate: the reactions of six chromium(VI) compounds
作者:D.H. Kerridge、S.A. Tariq、A.M. Wei
DOI:10.1016/0040-6031(86)85147-4
日期:1986.9
tetrahydrate as a molten salt solvent has a working range of 50°C before significant evaporation takes place, which can be extended to 90°C by covering the melt surface with a film of immiscible organic liquid. Potassium di-, tri- and tetrachromates dissolved but did not react until the temperature range of anhydrous calcium nitrate, when Lux-Flood acid-base reaction occurred forming chromate. Potassium chromate
The Standard Gibbs energies of formation of ACrO4 (A = Ca, Sr or Ba) from EMF measurements
作者:A.M. Azad、R. Sudha、O.M. Sreedharan
DOI:10.1016/0040-6031(92)80011-k
日期:1992.1
electrolyte EMF method, there is no reliable thermodynamic information on SrCrO 4 . Hence the EMF of the galvanic cells Pt,O 2 (g)/ CaO,CaF 2 /CaF 2 /AF 2 ,ACrO 4 ,Cr 2 O 3 /Pt,O 2 (g) were studied under an atmosphere of pure oxygen at a pressure of 0.1 MPa over the ranges 788–1070, 851–1116 and 850–1168 K where A is Ca, Sr and Ba respectively. From the cell EMF data, the standard Gibbsenergies of formation
Synthesis and Structure of Novel CrV–CrVI Mixed Valence Compounds, Nd1−xCaxCrO4 (x=0.02–0.20)
作者:Y. Aoki、H. Konno
DOI:10.1006/jssc.2000.9008
日期:2001.2
method. The calculated densities of Nd1−xCaxCrO4 (x=0–0.20) were in good agreement with the ones measured by the picnometry. XPS and Raman spectra indicated that Nd1−xCaxCrO4 (x=0.02–0.20) are mixedvalence oxides containing two types of tetrahedra, CrVO3−4 and CrVIO2−4, having D2d symmetry in the structure, and this compensates the decrease of positive charges introduced by CaII ions. Though two types
单相的Nd 1- X的Ca X的CrO 4(X = 0-0.20)氧化物通过选自Nd制备前体的热解合成的III -Ca II -Cr VI混合溶液。的Nd 1- X的Ca X的CrO 4具有X ≥0.25没有作为单相获得。所有Nd 1- x Ca x CrO 4均为锆石类型(四方晶系,I 4 1 / amd),组成几乎是化学计量的,没有任何本质上的缺陷,这是通过化学分析确定的。晶格常数和原子位置通过X射线Rietveld方法精制。Nd 1- x Ca x CrO 4(x = 0-0.20)的计算密度与通过皮法测量的密度相吻合。XPS和拉曼光谱表明的Nd 1- X的Ca X的CrO 4(X = 0.02〜0.20)是含有两种类型的四面体,铬混合价氧化物V ø 3- 4和Cr VI ö 2- 4,具有结构中的D 2d对称,这补偿了由Ca II离子引入的正电荷的减少。尽管无法通过XRD区分两种类