noun
definition
A chemical element (symbol Cr) with an atomic number of 24: a steely-grey, lustrous, hard and brittle transition metal.
Examples of chromium in a Sentence
Chromium has been discovered in Tasmania also.
Among the minerals are silver, platinum, copper, iron, lead, manganese, chromium, quicksilver, bismuth, arsenic and antimony, of which only iron and manganese have been regularly mined.
Uranium is chemically related to chromium, molybdenum and tungsten.
Sodium and potassium hydroxide solutions precipitate green chromium hydroxide from solutions of chromic salts; the precipitate is soluble in excess of the cold alkali, but is completely thrown down on boiling the solution.
Moissan (Comptes rendus, 1893, 116, p. 349; 1894, 119, p. 185) reduces the sesquioxide with carbon, in an electric furnace; the product so obtained (which contains carbon) is then strongly heated with lime, whereby most of the carbon is removed as calcium carbide, and the remainder by heating the purified product in a crucible lined with the double oxide of calcium and chromium.
Thechromites maybe looked upon as salts of chromium sesquioxide with other basic oxides, the most important being chromite (q.v.).
Oxyhalogen derivatives of chromium are known, the oxychloride, CrO 2 C1 21 resulting on heating potassium bichromate and common salt with concentrated sulphuric acid.
By the action of concentrated sulphuric acid it is transformed into chromium ammonium sulphate.
Chromium salts readily combine with ammonia to form complex salts in which the ammonia molecule is in direct combination with the chromium atom.
P. Pfeiffer (Berichte, 1904, 37, p. 4 2 55) has shown that chromium salts of the type [Cr{C2H4(NH2)2}2X2]X exist in two stereo-isomeric forms, namely, the cisand transforms, the dithiocyan-diethylenediamine-chromium salts being the transsalts.
These exhibit, in certain cases, marked crystallographical and other analogies with the corresponding salts of chromium and ferric iron.
For instance, following Krupp's formula, the side and barbette armour of war-vessels is now generally if not universally made of nickel steel containing about 3.25% of nickel, 0.40% of carbon, and 1.50% of chromium, deeply carburized on its impact face.
Chrome steel, which usually contains about 2% of chromium and o 80 to 2% of carbon, owes its value to combining, when in the " hardened " or suddenly cooled state, intense hardness with a high elastic limit, so that it is neither deformed permanently nor cracked by extremely violent shocks.
But the improvement may be due wholly to the considerable chromium content of these socalled vanadium steels.
Chrome-tungsten or High-speed Steel.-Steel with a large content of both chromium and tungsten has the very valuable property of " red-hardness," i.e.
This effect of chromium, tungsten and carbon jointly consists essentially in raising the " tempering temperature," i.e.
It unites with sulphuric acid giving an acid salt, T1HSO 4.3H 2 O, and with aluminium, chromium and iron sulphates to form an "alum."
They can be distinguished from the corresponding bromides and iodides by the fact that on distillation with a mixture of potassium bichromate and concentrated sulphuric acid they yield chromium oxychloride, whereas bromides and iodides by the same treatment give bromine and iodine respectively.
With potassium bichromate solution, which is yellow, the iron solution becomes green from the chromium chloride or sulphate formed, and the end of the reaction is determined by removing a drop of the solution on the stirring-rod and adding it to a drop of a dilute solution of potassium ferricyanide on a white tile.
Chromium trioxide dissolves readily in water, and the solution is supposed to contain chromic acid, H 2 CrO 4; the salts of this acid are known as the chromates.
In addition to these normal salts, others exist, namely bichromates, trichromates, &c., which may be regarded as combinations of one molecular proportion of the normal salt with one or more molecular proportions of chromium trioxide.
They may also be prepared by oxidizing chromium salts (in alkaline solution) with hydrogen peroxide, chlorine, bleaching powder, potassium permanganate and manganese dioxide.
They are easily reduced in acid solution by sulphuretted hydrogen, and also by sulphur dioxide to chromium salts.
When heated in a current of sulphuretted hydrogen, or carbon bisulphide, it yields a mixture of chromium sesquioxide and sulphide.
When heated with sulphur it yields chromium sesquioxide.
They are readily decomposed by heat, leaving a residue of the normal chromate and chromium sesquioxide, and liberating oxygen; ammonium bichromate, however, is completely decomposed into chromium sesquioxide, water and nitrogen.
Sulphuretted hydrogen and sulphur dioxide reduce them in acid solution to the condition of chromium salts.
Sodium bichromate, Na 2 Cr 2 0 7.2H 2 0, may be obtained by the addition of the requisite quantity of chromium trioxide to a solution of sodium chromate.
Among such substances are fireclay and firebricks, certain sandstones, silica in the form of ganister, and Dinas stone and bricks, ferric oxide and alumina, carbon (as coke and graphite), magnesia, lime and chromium oxide - their relative importance being indicated by their order, the last two or three indeed being only of limited use.
Oxide of chromium and chrome iron ore have been proposed as refractory crucible materials.
Composite coatings of electroless nickel containing silicon carbide exhibits superior abrasive wear resistance to hard chromium plate in some applications.
It was, therefore, decided to investigate the deposition of chromium carbide onto the tool in question.
It contains the essential mineral chromium to help regulate sugar cravings.
The foremost concern for persons with diabetes who use chromium is the development of kidney problems.
For example, leather gloves are required to have a chromium VI content less than the limit of detection.
Constant craving According to naturopathic doctor Joseph Mercola, some people find that chromium may also help control sugar and carbohydrate cravings.
No significant side effects were observed in people taking chromium.
Spray given off from vessels at which an electrolytic chromium process is carried on, except trivalent chromium.
To achieve this standards, small amounts of a reducing agent are added where necessary to control the quantity of soluble chromium.
Recommendations and guidelines are provided for dietary chromium in domestic animal species.
Is this because cast gold has a higher, or lower, modulus of elasticity compared to cobalt chromium?
With their high chromium concentration, they have excellent pitting and crevice corrosion resistance, and to chloride stress corrosion.
The Toda flywheel is marketed as ' ultra light ' and is manufactured from chromium molybdenum steel for the highest quality.
The very good chromium plating cost an additional DM 342.
In this paper the oxygen K edges from a variety of chromium spinels and magnesium aluminate are presented.
Cooking or preparing foods using stainless steel utensils may add significant amounts of chromium to the diet.
For example, at first he represented ferrous and ferric oxides by the formulae Fe02, Fe03, and by the analogy of zinc and other basic oxides he regarded these substances as constituted similarly to Fe02, and the acidic oxides alumina and chromium oxide as similar to FeO 3.
Goldschmidt has prepared the metal from the oxide by means of his "thermite" process (see Chromium).
Hydrochloric acid and its metallic salts can be recognized by the formation of insoluble silver chloride, on adding silver nitrate to their nitric acid solution, and also by the formation of chromium oxychloride (see above).
In his researches, Roscoe showed that the atomic weight of the metal as determined by Berzelius and the formulae given to the oxides were incorrect, and pointed out that the element falls into its natural place in group V of the periodic classification along with phosphorus and arsenic, and not in the chromium group where it had originally been placed.