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Like iron, this silvery heavy metal can be forged relatively well, rolled into sheet metal or drawn into wire. Like iron and cobalt, it is ferromagnetic, but not quite as good. When heated above its Curie temperature of 627 Kelvin (+353.85 ° C), nickel loses its ferromagnetic properties. Iron-nickel alloys with a proportion of 29% nickel are not ferromagnetic, they are suitable for machines that must not be magnetizable. Iron-nickel alloys with a high nickel content of up to 80% have a high permeability, so they are excellent at shielding magnetic fields. Finely divided nickel absorbs large amounts of hydrogen at higher temperatures. Hydrogen can easily pass through hot nickel sheet.
Ferromagnetism in nickel

Nickel is attracted to a magnet.

In its chemical behavior, nickel is similar to cobalt and iron. In compact form, it is resistant to air, water, non-oxidizing acids such as hydrochloric acid, alkalis and most organic substances at room temperature. Dilute nitric acid attacks nickel with the formation of hydrogen and nickel nitrate, while with concentrated nitric acid passivation occurs because a thin oxide layer is formed. Finely divided nickel powder can have pyrophoric properties; it ignites by itself. A hot nickel wire burns in pure oxygen with sparks to form nickel (II) oxide. Hot nickel also reacts with the halogens, with phosphorus, sulfur, arsenic, boron and silicon. The resulting nickel salts are sometimes black, but mostly colored compounds with a green, yellow or blue color.

Detect nickel ions with dimethylglyoxime

After adding a 1% dimethylglyoxime solution in alcohol
a red complex is formed when a dilute nickel (II) sulfate solution is added.

The detection of nickel and its salts is carried out with the complexing agent dimethylglyoxime (Tschugaeff's reagent). This forms with Ni2+-Ions form a raspberry-red complex that is sparingly soluble in water. In professional chemical analyzes, iron ions that were previously troublesome are removed by boiling them in hydrogen peroxide. The analysis is carried out in ammoniacal solution. At school you can use a 1% dimethylglyoxime solution in 96% alcohol or denatured alcohol and do without pretreatment. If the reagent is dropped into a nickel (II) sulfate solution, the typical red precipitate is formed. If a cotton swab is moistened with the reagent, nickel can be detected in coins or in pieces of jewelry if these have been intensely wetted by skin sweat beforehand.

Detection of nickel in coins

If you rub cotton swabs soaked with dimethylglyoxime solution on coins containing nickel,
the sticks take on a slightly reddish color when the coins come into contact with sweat.