Hello everyone. In this video, I would like to tell you about the properties of such a metal as cobalt, and also about why its compounds are added to a cat's litter tray. In the periodic table of chemical elements, cobalt is located in Group 9 (IX), between iron and nickel in the so-called "ferro-magnetic pyramid". The history of the use of cobalt dates back from thousands of years ago, because since the Bronze Age its compounds have been added to glass, which have a beautiful blue tint. Nowadays, cobalt is mostly extracted from cobalt containing minerals which are mined along with nickel and copper. And in this process, cobalt is a by-product. After being electrolytically refined, pure metallic cobalt looks like gray metal, the density of which is similar to that of copper. As I mentioned earlier, cobalt is a ferromagnetic —or in other words, it strongly attracts to magnets— and it can also get magnetized when placed in close vicinity to a strong magnetic field. I even managed to magnetize a piece of cobalt, which is why it began to get attracted
to other cobalt pieces. Because of this property, this metal is used to make a magnetic alloy with samarium. Cobalt-samarium (SmCo) magnets have much stronger magnetic properties than usual ferrite magnets, and also higher operating temperatures. Speaking of the chemical properties of cobalt, what really stands out
is this metal's resistance to oxidation. When pierced in air, a piece of cobalt oxidizes just a little, slightly fading as a result of reacting with oxygen. It is also worth of note how this metal's colour changes depending on its vicinity to a burner. First, when cobalt is exposed to air, it forms a complex cobalt oxide, which when heated up to 900 degrees Celsius, decomposes into cobalt monoxide. After cooling down, cobalt monoxide is then oxidised, causing the metal to fade again. Cobalt doesn't react with acids very actively. It almost doesn't react with hydrochloric acid at all, but when mixed with nitric acid, it reacts much better, producing a reddish cobalt nitrate solution. Actually, almost half of all cobalt compounds in normal conditions are red. For instance, as in the case with cobalt chloride or cobalt sulphate, a double salt ammonium cobalt sulphate can be used to produce such beautiful red crystals, which have beautiful symmetrical forms. However, there are other cobalt compounds, which we are going to synthesize now. For instance, if potassium thiocyanate is added to cobalt sulphate, there will be no reaction in water. But if acetone is added to the test tube the top layer of the solution will turn blue. It is so, because tetracyanocobaltate is not synthesized in water because of disruption of the chemical balance. But in the organic solution, which is devoid of water, blue pigment can form and remains stable. You can run this same reaction by grinding a mixture of two same reagents. At the same time, red content of the mortar turns bright blue forming the same cobalt complex. These reactions make it clear that cobalt compounds can also be blue, depending on the conditions and water content. Manufacturers producing silica-gel based cat litters employ this principle by adding such blue granules. Expensive cat litters' blue granules turn pink when soaked in water because they contain cobalt chloride, which also changes its color depending on moisture content. This colour change indicates that litter granules need to be changed. In cheaper litters, cobalt chloride is substituted by cheaper food dyes, such as indigo carmine or methylene blue. Since the early 2000s, cat litters containing cobalt chloride have been marked because this metal's compounds are not environmentally friendly and can even be toxic to pets. That is why if the label of your cat litter package doesn't mention cobalt, your cat is safe. Getting back to the chemical properties, besides blue and red, cobalt compounds can also be of other colours. For instance, if sodium hydroxide is added to cobalt chloride, the reaction will produce
green cobalt hydroxide sediment. Presence of Trilon-B will make
the green colour even more prominent. Also, if electric current is passed through a thin cobalt wire, the metal will heat up and melt, due to high metal resistance. And after that, you will see a green cobalt oxide, in the place where the wire broke. If this oxide is heated up with aluminium oxide to 1200 degrees centigrade, this reaction will produce a blue pigment— Cobalt blue—one of the first pigments used for painting porcelain in ancient China. It is still used to produce some dyes for artists. Speaking of more practical things, nowadays, cobalt has lots of practical applications. Pure cobalt is added to steel in order to improve its durability and hardness. Such steel is used to make very hard drills. Besides, cobalt is used in super-alloys which are mainly used to make heat-resistant elements of aircraft engines. Cobalt oxide is still used to dye glass a saturated blue colour. Such glass is rare, because it's quite expensive. Furthermore, the majority of extracted cobalt is used to produce lithium-ion batteries because lithium cobaltate is used as the anode in them. The battery of your mobile phone is likely to contain more than 10 grams of this chemical. Nowadays, because of the growing demand for cobalt, the extent of its mining is growing too, as well as this metal's price which has grown four times in the last two years. However, since most cobalt is mined in Africa —in Congo to be precise— there are lots of conflicts among the local gangs controlling mining of this metal. Cobalt, along with tantalum, can be considered the most conflict-causing metals, the mining of which, for
manufacturing smartphone batteries, costs hundreds of human lives. However, lets leave it at that. Cobalt also plays an important role in our body, because it is one of the B- group vitamins, Vitamin B12. Upon dissolving of tablets containing B-group vitamins, the solution turns pink because it contains cobalt complex. For instance, pure cyanocobalamine is red, and it has the most complex structure among all vitamins in our body. It serves as a cofactor in several enzyme reactions, which collectively play a very important role in the production of new blood cells. However, overdose of cobalt compounds is toxic, despite the fact that a small amount of it is vital to health. To sum up, such an unusual metal as cobalt has lots of applications, from cats' litters to smartphone batteries. If you would like to support the continuous production of science videos like this one, please support channel on Patreon. Link in the video description. Please like this video and subscribe to my channel to see many more new and interesting videos. ♪ ♪
