Nickel, properties of the atom, chemical and physical properties

Nickel sulfate in bags. Aqueous solutions of nickel(II) salts contain hexaaquanickel(II) ion [Ni(H2O)6]2+. When an ammonia solution is added to a solution containing these ions, nickel(II) hydroxide, a green, gelatinous substance, precipitates. This precipitate dissolves when excess ammonia is added due to the formation of hexaamine nickel(II) ions [Ni(NH3)6]2+.

Nickel forms complexes with tetrahedral and planar square structures. For example, the tetrachloronicickelate (II) [NiCl4]2− complex has a tetrahedral structure, and the tetracyanonickelate(II) complex [Ni(CN)4]2− has a planar square structure.

Qualitative and quantitative analysis uses an alkaline solution of butanedione dioxime, also known as dimethylglyoxime and Chugaev's reagent, to detect nickel(II) ions. The fact that this substance is a reagent for nickel was established in 1905 by L. A. Chugaev. When it reacts with nickel(II) ions, the red coordination compound bis(butanedionedioximato)nickel(II) is formed. It is a chelate compound and the butanedione dioximate ligand is bidentate.

General information:

Receipt

The total reserves of nickel in ores at the beginning of 1998 are estimated at 135 million tons, including reliable reserves of 49 million tons. The main nickel ores - nickel (kupfernickel) NiAs, millerite NiS, pentlandite (FeNi)9S8 - also contain arsenic, iron and sulfur; igneous pyrrhotite also contains pentlandite inclusions. Other ores from which Ni is also mined contain impurities of Co, Cu, Fe and Mg. Nickel is sometimes the main product of the refining process, but more often it is obtained as a by-product in other metal processes. Of the reliable reserves, according to various sources, from 40 to 66% of nickel is in “oxidized nickel ores” (ONR), 33% in sulfide ores, 0.7% in others. As of 1997, the share of nickel produced by OHP processing was about 40% of global production. In industrial conditions, OHP is divided into two types: magnesium and ferruginous.

Refractory magnesium ores, as a rule, are subjected to electric smelting using ferronickel (5-50% Ni + Co, depending on the composition of the raw material and technological features).

The most ferrous - laterite ores are processed by hydrometallurgical methods using ammonia-carbonate leaching or sulfuric acid autoclave leaching. Depending on the composition of the raw materials and the technological schemes used, the final products of these technologies are: nickel oxide (76-90% Ni), sinter (89% Ni), sulfide concentrates of various compositions, as well as metal electrolytic nickel, nickel powders and cobalt.

Less ferrous nontronite ores are smelted into matte. At full-cycle enterprises, the further processing scheme includes conversion, matte firing, and electric smelting of nickel oxide to produce metallic nickel. Along the way, the recovered cobalt is released in the form of metal and/or salts. Another source of nickel: in the coal ash of South Wales in England - up to 78 kg of nickel per ton. The increased nickel content in some coals, oils, and shale indicates the possibility of nickel concentration in fossil organic matter. The reasons for this phenomenon have not yet been clarified.

“Nickel for a long time could not be obtained in plastic form due to the fact that it always contains a small admixture of sulfur in the form of nickel sulfide, located in thin, brittle layers at the boundaries of the metal. Adding a small amount of magnesium to molten nickel converts the sulfur into the form of a compound with magnesium, which is released in the form of grains without affecting the ductility of the metal.”

The bulk of nickel is obtained from garnierite and magnetic pyrite.

1. Silicate ore is reduced with coal dust in rotary tube kilns to iron-nickel pellets (5-8% Ni), which are then cleaned of sulfur, calcined and treated with an ammonia solution. After acidifying the solution, metal is obtained from it electrolytically.
2. Carbonyl method (Mond method). First, copper-nickel matte is obtained from sulfide ore, over which CO is passed under high pressure. Highly volatile tetracarbonylnickel [Ni(CO)4] is formed, the thermal decomposition of which produces a particularly pure metal.
3. Aluminothermal method for the recovery of nickel from oxide ore: 3NiO + 2Al = 3Ni +Al2O3

Chemical properties of nickel:

Application

In 2015, 67% of nickel consumption came from stainless steel production, 17% from non-iron alloys, 7% from nickel plating and 9% from other applications such as batteries, powder metallurgy and chemical reagents.

Alloys

Nickel is the basis of most superalloys - heat-resistant materials used in the aerospace industry for power plant parts.

• Monel metal (65-67% Ni + 30-32% Cu + 1% Mn), heat-resistant up to 500 °C, very corrosion-resistant;
• white gold (for example, 585 standard contains 58.5% gold and an alloy (ligature) of silver and nickel (or palladium));
• nichrome, an alloy of nickel and chromium (60% Ni + 40% Cr);
• permalloy (76% Ni + 17% Fe + 5% Cu + 2% Cr), has high magnetic susceptibility with very low hysteresis losses;
• invar (65% Fe + 35% Ni), almost does not expand when heated;
• In addition, nickel alloys include nickel and chromium-nickel steels, nickel silver and various resistance alloys such as constantan, nickel and manganin.
• Nickel is present as a component of a number of stainless steels.

Nickel plating

Nickel plating is the creation of a nickel coating on the surface of another metal to protect it from corrosion. It is carried out by electroplating using electrolytes containing nickel(II) sulfate, sodium chloride, boron hydroxide, surfactants and gloss agents, and soluble nickel anodes. The thickness of the resulting nickel layer is 12–36 microns. The stability of the surface gloss can be ensured by subsequent chrome plating (chrome layer thickness - 0.3 microns).

Currentless nickel plating is carried out in a solution of a mixture of nickel(II) chloride and sodium hypophosphite in the presence of sodium citrate:

NiCl2 + NaH2PO2 + H2O → Ni + NaH2PO3 + 2HCl

The process is carried out at pH 4-6 and 95 °C.

Battery production

Production of iron-nickel, nickel-cadmium, nickel-zinc, nickel-hydrogen batteries.

Chemical Technology

In many chemical technological processes, Raney nickel is used as a catalyst.

Radiation technologies

The nuclide 63Ni, which emits β particles, has a half-life of 100.1 years and is used in krytrons, as well as electron capture detectors (ECDs) in gas chromatography.

Medicine

• Used in the manufacture of bracket systems (titanium nickelide).
• Prosthetics.

Coinage

Nickel is widely used in the production of coins in many countries. In the United States, the 5-cent coin is colloquially known as the nickel.

Music industry

Nickel is also used for winding strings of musical instruments.

Nickel prices

During 2012, nickel prices fluctuated between $15,500 and $17,600 per ton.

Physical properties of nickel:

Zinc

In general, the division of zinc into groups according to purpose (casting, deformable, antifriction, tread, solders) and chemical composition (zinc-copper, zinc-aluminum, zinc-magnesium systems) is quite arbitrary, since some alloys are also used for casting, extrusion and as an antifriction material, and also contain aluminum, copper and magnesium in composition.
Physical properties of zinc

Zinc is a bluish-silver shiny metal; in air it quickly oxidizes, becoming covered with a thin protective film that reduces its shine; has a low melting point. The volume of metal during melting increases in accordance with the decrease in density. With increasing temperature, the kinetic viscosity and electrical conductivity of zinc decrease and its electrical resistivity increases. The most common and important physical characteristics of zinc are presented below:

Position of zinc in the periodic table of elements

Currently, in almost all industrialized countries there is a large shortage of non-ferrous metals. Therefore, a scientifically based approach to the selection and rational use of metals, including zinc and its compounds, is necessary.

The most general idea of ​​the properties of zinc and possible changes in these properties is given by the fundamental law discovered by D.I. Mendeleev, which establishes the periodic change in the properties of chemical elements. According to this law, the properties of elements and metals in particular are determined by the electronic structure of atoms. It is the magnitude of the charge of the atomic nuclei that determines the place occupied by each metal in the periodic table.

The division of elements into metals and non-metals is conditional. However, it should be noted that metallic properties increase with increasing atomic mass and with increasing number of electron shells. According to the electronic structure (ls22s22p63s23p63d104s2), zinc is a typical metal, located in the secondary subgroup of the second group in the system of elements. It has an oxidation state of +2, i.e. in chemical compounds it is a divalent ion. This is due to the fact that greater energy is required to remove the third electron.

The constant valence of zinc, equal to two, is apparently due to the maximum filling of the d-layer and the high value of the ionization potential: Zn2+ - Zn3+.

According to modern concepts, the process of metal ionization occurs in stages: the rate of electron removal at each stage may not be the same. When zinc is dissolved in electrolytes (for example, during corrosion in aqueous solutions), if we take into account the above ionization energy values, we can expect the formation of first a monovalent zinc ion, then a divalent one. Experimentally, only Zn2+ can be determined. The properties shown, as well as the physical properties of zinc given below, allow us to classify it as a non-transition element.

The position of zinc in the periodic table of elements, initially determined by its atomic mass of 65.37, determines a number of properties inherent only to it - physical and chemical, which will be discussed below. Here it should only be noted that the observed differences in properties are sometimes due to the participation of zinc isotopes in the processes.

Table 1. Some isotopes of zinc

Consequently, the position of zinc in the periodic table, determined by its nature, makes it possible to predict the properties of its compounds, as well as interaction with the external environment.

Metallochemical properties of zinc

Zinc is characterized by the presence of two electrons in the 4s outer shell. The main difference between zinc and group II metals is that it has a 3d shell completely filled with ten electrons (alkaline earth metals do not have peripheral d shells). This electronic structure of zinc determines the peculiarities of its physicochemical and other properties, as well as its difference from metal groups.

In the zinc subgroup there are very original combinations of properties of transition and non-transition elements. On the one hand, since zinc does not exhibit variable valency and does not form compounds with an unfilled d-layer, it should be classified as a non-transition element. This is also evidenced by some physical properties of zinc (low melting point and hardness, high electropositivity compared to its closest “neighbors” in the transition series). On the other hand, zinc can also be classified as a transition element, given its tendency to complex formation reactions. The diffusive nature of the d-orbitals makes zinc easily deformable.

The metallochemical properties of zinc, which determine the nature of its interaction with other elements, are sharply different from the metallochemical properties of the alkaline earth group metals. Based on an assessment of the difference in the values ​​of atomic radii, ionization potentials (Fig. 1, b) and electronegativity (Fig. 1, c) of the elements of the periodic table and zinc, taking into account double phase diagrams (Fig. 2), the following conclusions were made:

1. Under normal conditions, zinc is a typical electronegative metal and forms chemical compounds with many electropositive metals, with the exception of those that have electronegativity values ​​close to zinc. The latter include, for example, Cd, Tl, Pb, In, Ca, Ge.

2. Under normal conditions, zinc does not form continuous solid solutions with any element of the periodic table.

3. Zinc is characterized by the formation of limited solid solutions, for example with Li, Mg, Cr, Mn, Fe, Co, Ni, Cu, Cd, Al, In, Tl, Sn, Pb. At the same time, the solubility of zinc in electropositive metals (Li, Mg, Tl, Mn, Cd) is significantly higher at appropriate temperatures than these metals in zinc.

4. Zinc under normal conditions does not interact with Mo, W, Re, B, C, Si, N. There is no information yet on the interaction of zinc with Pb, Cs, Y, Nb, Ta, Re, Os, Ru, Po, At.

Thermodynamic properties of zinc

Zinc, alloys and chemical compounds based on it are widely used in technology. To meet consumer requirements, they must have certain properties. Thus, zinc and zinc alloys, as a rule, must be stable when exposed to the environment. The production of chemical compounds is based on the instability of zinc under specific conditions, for example, in certain acids, alkalis, and salts. Consequently, depending on the formulation of the problem, zinc should be stable or subject to change. Thermodynamics provides a fundamental answer to these questions.

Currently, extensive reference material has been accumulated that allows one to determine the capabilities of a particular process without conducting special studies. Therefore, a prediction of the applicability of zinc for specific practical purposes can be made based on data on its thermodynamic properties.

Under the influence of internal and external factors, zinc can change from one state to another. Such a transition in the most general form can be expressed in terms of the energy of the system: GI = GII, where GI is the energy of the system in the initial state, for example, zinc, which does not change under these specific conditions; GII is the energy of a system in a new state, for example a chemical compound of zinc. Consequently, a measure of the stability of the system is the change in energy that serves as the driving force of the process: AG = GII - GI.

Currently, the thermodynamic laws of changes in the state of systems have been sufficiently studied and described. Within the framework of this book, it should only be noted that to describe the system, the so-called thermodynamic potentials are used: internal energy U = f(S, V, N, xi); enthalpy H = f(S, P, N, xi); Helmholtz energy A = f(V, T, N, xi); Gibbs energy G = f(P, T, N, xi), where S is entropy; V—volume; P—pressure; T-temperature; xi - other variable parameters of the function; N is the number of particles of the system.

The energies considered are determined using simple equations (Table 2). Using the indicated equations and reference data on the values ​​of the parameters, as well as knowing the conditions and modes of the planned process, it is possible to fundamentally determine whether it is possible, and if possible, its direction.

Table 2. Some equations for calculating thermodynamic parameters

For ease of use, the considered equations in Table. 3-6 presents the numerical values ​​of the system parameters

Table 3. Thermodynamic properties of zinc and its compounds

Table 4. Heat capacities of substances, J/(mol ⋅ K) CP = a + bT + c'T⁻²

Note: l - liquid, j - crystalline, g - gaseous.

Table 5. Change in Gibbs energy (J/mol) for some reactions

∆G⁰T = A + CT; ∆GT = A + BTlgT + CT

Table 6. Thermodynamic properties of inorganic substances in aqueous solution S⁰₂₉₈

As can be seen, based on their comparison, as well as calculation of properties for specific temperature conditions, it is possible to assess the preference of processes, their possibility or impossibility.

In the above tables: C0p298 = 36.8 J/ (mol • K); CP—heat capacity at constant pressure; ΔG°f298 is the Gibbs energy at 298.15 K; ΔН°f0 and ΔH°f298 are the enthalpy of formation of compounds at 0 and 298.15 K, respectively: S0298 is the standard entropy at 298.15 K.

5. Electrochemical and chemical properties

Most natural environments, solutions of acids, alkalis and salts are electrolytes. Therefore, the behavior of zinc in them (primarily corrosion) is determined by its electrochemical properties. A feature of electrochemical reactions is that they occur with the participation of free electrons and mainly with the spatial separation of oxidation and reduction processes (coupled reactions). An example is the corrosion reaction of zinc in an aqueous solution: Zn + 2H2O → Zn(OH)2 + H2, where Zn is 2e → Zn2+, 2H+ + 2e → H2. The processes of applying galvanic and chemical zinc coatings, as well as the dissolution of zinc during anodic polarization, are based on electrochemical reactions.

From the considered thermodynamic phenomena, it is obvious that any process can occur spontaneously only at ΔG < 0. For redox processes that occur when a metal is immersed in an electrolyte, the change in the Gibbs energy is determined from the expression: ΔG = -nφF, where n is the number of electrons participating in reaction; φ is the potential of the electrode process, determined by the Nernst equation.

To characterize metals, comparatively assess the possibility of the electrode process and the danger of contacts between metals, the so-called voltage series is often used: Li-K-Ba-Ca-Na-La-Nd-Mg-A1-Ti-Zr-Mn-V-Nb-Se -Cr-Te-Zn-Ga-Fe-Cd-Co-Ni-Mo-In-Sn-Pb-Ge-H2 (φ0= 0) -Bi-Cu-Hg-Ag-Pt-O2 (φ0 = 1.228) - Au.

From lithium to gold, the activity of the metal decreases and corrosion resistance increases. Consequently, when two metals come into contact, the one on the left will be susceptible to corrosion, and the farther the metals are from one another, the more dangerous their contact is (the stronger the contact corrosion). This is explained by the fact that the potential difference and, consequently, -ΔG, which is the driving force of the process, increases.

In the equations considered, the only variable parameter is the potential of the electrode process, and φo for the main electrode reactions is a reference value. Thus, without conducting any experiments, using it, you can determine ΔG0, i.e. possibility of electrode process.

Redox reactions of zinc in electrolytes, as a rule, involve two electrons. Its standard potential is 0.763 V; with an increase in temperature from 298 to 473 K, it increases to -0.750 V. Under these conditions, the Gibbs energy (ΔGfT) decreases from 147 to 145 kJ/mol. Obviously, the tendency of zinc to ionize decreases as the potential increases.

Under specific conditions, it is possible to determine L and calculate the value of φ.

The most complete relationship between the potential and the pH of water and the possible mechanism of the zinc dissolution process are established from the diagram shown in Fig. 3.

As can be seen in the figure, the potential of zinc depends on the pH value and ion activity, and under certain conditions there is an equilibrium between the liquid and solid phases. In general, the state of the system at the most characteristic points of the diagram is described by the equations given in Table. 7.

From the data presented above, one can judge the mechanism of redox processes when zinc is immersed in water.

To assess the comparative activity of zinc in aqueous solutions, the standard potentials of the electrode processes presented below are of interest, B:

Table 7 Main processes determining the thermodynamic state of zinc and its oxides in water

The above data reveal only the fundamental possibility of the process, not to mention its kinetics - speed. It should be noted that if the impossibility of a process is thermodynamically established, then practically it will not occur. However, even if the possibility of a process is established thermodynamically, it may also not proceed or proceed at an unequal rate, the value of which, as a rule, is determined experimentally. The difference between the theoretically determined and practically observed rates of the electrode process is due to the overvoltage n - the “resistance” of the reaction. Overvoltage is understood as a potential shift from the standard one during polarization of the metal, necessary for the occurrence of this particular electrode reaction, determined by the Tafel formula: n = a + b 1 gi, where a and b are constant coefficients; i is the polarization current density.

Experimentally, this dependence is determined very simply - by taking polarization curves (Fig. 4). As can be seen, at i = 1 A/cm2 n =a, i.e. characterizes the irreversibility of the electrode process. The value b (the tangent of the slope of the curve) characterizes the speed of the process. For some typical cases, for example, for the evolution of hydrogen on zinc in aqueous solutions of acids and alkalis, the values ​​of the coefficients a and b of the Tafel equation are presented below: for 1 n. H2SO4 a = 1.246V; b = 0.116 V; for 6 n. NaOH a = 1.23 V; b = 0.22 V.

Consequently, by setting the polarization current density, it is possible to determine the overvoltage of the electrode process. This in turn allows you to select polarization modes for the process.

The possibility of a chemical reaction is determined by the value of the Gibbs energy for the formation of compounds.

For most of the most important substances, the values ​​of the change in the Gibbs energy and the equilibrium constant under standard conditions (T = 298.15 K) are known and are reference values. This allows us to fundamentally evaluate the possibility of a reaction to form a chemical compound between any simple substances.

The chemical properties of zinc, like any other metal, mean its ability to interact with other substances by exchanging electrons, i.e. without the participation of free electrons. In this case, the product of a chemical reaction is a compound of interacting substances, for example 2Zn + O2 → 2ZnO.

The abilities discussed above, which determine the chemical properties of metals (zinc), also manifest themselves during their interaction with non-electrolytes (dry gases and organic substances).

At room temperature, zinc practically does not interact with most gaseous substances. Only when strongly heated does it begin to interact with atmospheric oxygen, chlorine gas, bromine, iodine, fluorine and many other gases. Zinc does not interact with nitrogen, hydrogen, or carbon. When heated, it reacts explosively with sulfur and phosphorus.

The generalized information discussed above about the electrochemical and chemical properties of zinc allows us to state their diversity and dependence on both the physical nature of the metal and external factors. Knowledge of the behavior of zinc under specific conditions, based on the general concepts presented, is of practical interest.

Mechanical and technological properties of zinc

The mechanical properties of zinc, especially tensile strength ( σв ), elongation ( δ ,%) and hardness (HB), depend significantly on the processing state of zinc. According to various studies, zinc in the cast state has the following mechanical properties: σв = 30-80 MPa, δ = 0.3-4.0%, НВ = 200-500 MPa.

At room temperature, zinc in the cast state has limited ductility and is difficult to roll, since deformation occurs only along the basal plane (001), i.e. parallel to the direction of crystal growth. In this regard, a sharp anisotropy in the properties of deformed zinc occurs. Moreover, zinc is much stronger across the rolling direction than along it.

Zinc in a deformed state is characterized by the following mechanical properties: σв = 140-250 MPa; δ = 15-50%; HB = 330-500 MPa.

The strength properties of zinc are highly dependent on temperature.

At temperatures below 0°C, zinc becomes embrittled, and as the temperature rises, ductility increases. Thus, at 100-150 °C, zinc becomes so plastic that it can be rolled into sheets with a thickness of hundredths of a millimeter. The ductility indicators of cast and deformed zinc at the same temperature are different. The maximum value of the relative elongation of deformed zinc is observed at 150 °C, and for cast zinc - within 200-300 °C, depending on the impurity content (Fig. 5).

Although zinc has high ductility when rolled in a wide temperature range, hot rolling of electrolytic zinc (grade Ts0) should be carried out at 150-200 °C, and printing zinc (grade TsZ) - at 180-220 °C. The purest zinc is easily forged and rolled in the temperature range of 150-200 °C. With increasing temperature, the hardness of cast zinc decreases (Fig. 6).

Impurities have a noticeable effect on the mechanical properties of zinc. Data on the influence of the main impurity elements on the hardness and impact strength of zinc are given in table. 8. The original zinc contained 0.019% Cd, 0.014% Pb, 0.001% Cu; the content of other controlled impurities was in the range of 0.001-0.008%. The effect of impurities was studied in the range from 0.1 to 3.0%.

From the table 8 it follows that magnesium has the strongest effect on the hardness of zinc in the direction of increase, and copper and iron have a somewhat lesser effect. Antimony and cadmium, up to 1%, slightly increase the hardness of zinc, but with an increase in the content of these elements in zinc above 1%, the hardness of zinc practically does not change. Lead and especially tin, within the considered limits, have virtually no effect on the hardness of the original zinc.

Table 8. Mechanical properties of zinc of various purities [according to Vol A.E.]

The greatest influence on the impact strength of zinc is exerted by iron and magnesium, as well as antimony, small amounts of which greatly reduce its values. Copper increases the impact strength of zinc, and tin, lowering it at first, gives a noticeable increase at a content of 3%. Cadmium and lead do not have a noticeable effect on the impact strength of zinc.

The structure of zinc also affects the mechanical properties of the cast metal. The mechanical properties of cast zinc containing 1.12% Pb, 0.11% Cd, 0.03% Fe and 0.002% Cu are given below:

σв = 74/27;δ = 1.6/0.1; an=3300/2300; HB = 470/440

The hardness of zinc varies from 200 to 500 MPa for coarse-grained and fine-grained structures, respectively. The columnar structure of cast zinc is characterized by anisotropy of properties. A study of the anisotropy of cast zinc on samples cut parallel and perpendicular to the direction of growth of columnar crystals showed the following: tensile strength was 540 and 160 MPa, and elongation was 4.5 and 1.5%, respectively. Therefore, the most favorable condition for plastic deformation of cast zinc will be the coincidence of the direction of the deforming force with the axis of the columnar crystals.

During the hot rolling process, the ductility of zinc after the first passes increases due to the transition of the cast structure to the deformed one. In this case, the number of crystals that are favorably oriented for deformation increases.

To transform the cast structure of high-purity electrolytic zinc into a deformed structure with complete recrystallization, a total reduction of 30-50% is sufficient, depending on the rolling temperature, and the transformation of the characteristic coarse-crystalline columnar structure of cast zinc into a deformed fine-grained structure occurs faster with increasing temperature.

Among the technological properties of zinc, special mention should be made of surface tension, wettability, viscosity, fluidity, and shrinkage.

The influence of individual elements on some technological properties of zinc is given in table. 9.

Zinc has good fluidity, which ensures good fillability of casting molds.

Table 9. Properties of zinc alloys containing various elements

Note. + improved properties; - deterioration of properties. *Depending on element concentration.

Remelting zinc, as a rule, worsens fluidity due to the enrichment of the melt with oxides. The surface tension of zinc also affects the fillability of the casting mold. Filling particularly thin casting elements (up to 3-5 mm thick) is associated with overcoming the surface tension of the metal, which for zinc decreases with increasing temperature and becomes equal to zero at a critical temperature. The dependence of surface tension and density of zinc on temperature (according to Benyakovsky M.A.) is expressed by the following relationships: o = 754-0.090 (t-419), y = 6.59-0.00097 (t-419), where t, °C

Impurities have a significant impact on the surface tension of zinc, therefore, by introducing small additives of some elements into the melt, the technological properties of zinc can be improved. These should be elements that lower the surface tension at the interface between a liquid-gas or two liquids: surface-active elements. In relation to the molten

Nickel crystal lattice:

Physiological action

Nickel and its compounds are toxic and carcinogenic.

Nickel is the main cause of allergies (contact dermatitis) to metals that come into contact with the skin (jewelry, watches, denim studs). In 2008, nickel was named Allergen of the Year by the Contact Dermatitis Society of America. The European Union limits the nickel content in products that come into contact with human skin.

In the 20th century, it was found that the pancreas is very rich in nickel. When nickel is administered after insulin, the action of insulin is prolonged and thus hypoglycemic activity increases. Nickel affects enzymatic processes, the oxidation of ascorbic acid, and accelerates the transition of sulfhydryl groups to disulfide groups. Nickel can inhibit the action of adrenaline and lower blood pressure. Excessive intake of nickel into the body causes vitiligo. Nickel is deposited in the pancreas and parathyroid glands.