Chromium

“ The principal chrome mineral is chromite, an oxide of chromium and iron. Chromite is a common minor constituent of basic igneous rocks of the peridotite and pyroxenite type. In these rocks it occurs both as disseminated grains, and as stringers, and large irregular masses which probably represent magmatic segregations. Alteration, and weathering of the parent rock, forming first serpentine and then residual clays, make the chromite bodies progressively richer and more available, by leaching out the soluble constituents of the rock leaving the chromite as residual concentrates. ”

“ Oxyhalogen derivatives of chromium are known, the oxychloride, CrO2Cl2, resulting on heating potassium bichromate and common salt with concentrated sulphuric acid. It distils over as a dark red liquid of boiling point 117° C., and is to be regarded as the acid chloride corresponding to chromic acid, CrO2 (OH) 2. It dissolves iodine and absorbs chlorine, and is decomposed by water with formation of chromic and hydrochloric acids; it takes fire in contact with sulphur, ammonia, alcohol, &c., and explodes in contact with phosphorus; it also acts as a powerful oxidizing agent. ”

“ 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. Chromic acid and its salts, the chromates and bichromates, can be detected by the violet coloration which they give on addition of hydrogen peroxide to their dilute acid solution, or by the fact that on distillation with concentrated sulphuric acid and an alkaline chloride, the red vapours of chromium oxychloride are produced. ”

“ The metallic chromium thus obtained has the appearance of a fine light-grey powder which is seen to be crystalline under the microscope; its sp. gr. at 16° is 6·7284. It fuses (with anhydrous borax) only at the highest temperatures, and after fusion presents a silver-white fracture. The strongest magnet has no action upon it.
Moissan (1893) obtained chromium by reducing the oxide Cr2O3 with carbon in the electrical furnace (Chapter VIII., Note 17) in 9–10 minutes with a current of 350 ampères and 50 volts. The mixture of oxide and carbon gives a bright ingot weighing 100–110 grams. ”

“ Chem., 1898, 25, p. 729; 1899, 30, p. 481; 1900, 34, p. 385) , namely active and inactive chromium; while W. Ostwald (ibid., 1900, 35, pp. 33, 204) has observed that on dissolving chromium in dilute acids, the rate of solution as measured by the evolution of gas is not continuous but periodic. It is largely made as ferro-chrome, an alloy containing about 60-70% of chromium, by reducing chromite in the electric furnace or by aluminium. ”

“ Manganese and chromium, while belonging to different families, have so many features in common in their chemical conduct that they may be studied together with advantage. They differ from most of the elements so far studied in that they can act either as acid-forming or base-forming elements. As base-forming elements each of the metals forms two series of salts. In the one series, designated by the suffix "ous," the metal is divalent ”

“ Bichromates.—The bichromates are usually of a red or reddish-brown colour, those of the alkali metals being readily soluble in water. 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. ”

“ Equal quantities of flowers of sulphur and bichromate of potash are thoroughly mixed, and heated to redness in a crucible, producing a mixture of oxide of chromium with sulphide and sulphate of potash. The latter are dissolved out by washing repeatedly with hot water, leaving the chromium oxide as a finely comminuted dense powder of an intense green colour. ”

“ When the copper is no longer coated, but remains clean and bright when immersed in the fluid, all the silver has been deposited, and the glass now contains a solution of copper.
Nearly all the colors used in the arts are produced by metals and their combinations; indeed, one is named chromium, from a Greek word signifying color, on account of the beautiful tints obtained from its various combinations with oxygen and the other metals. ”

“ It is especially useful in chemical apparatus that must withstand great extremes of temperature, because its experience has so tempered it that nothing less than a heat equal to that of the sun would give it much concern.
Another interesting thing about the slag from chromium thermit is that small rubies have been found in it. The scientific explanation is that they are nothing but crystallized alumina, coloured with chromium. The jewels usually are too small for any commercial purpose but serve as a very striking example of the intensity of the thermit fire. ”

“ If a sufficient quantity of sulphuric acid be present, the chromium sulphate and the potassium sulphate combine, forming chrome13 alum crystals, octahedron in form, similar to those of ordinary alum, but of a beautiful dark violet colour. The same are used in both the carbon and collotype processes. Bichromate of ammonium is easily decomposed by fire by heating it in a dry state. ”

“ Self-hardened steel is an alloy of iron, carbon, tungsten, and manganese, and some brands contain chromium in addition to these, and it is claimed, and probably truly, that the chromium improves the quality of the steel. ”

“ A dark green pigment prepared from oxide of chromium; mixed with Prussian blue and chrome yellow it is called Green Cinnabar.
Chrome Ochre. Oxide of chromium of a fine yellowish green.
Chrome Red. A chromate of lead; a durable pigment used in oil painting. (See Red Lead.)
Chrome Yellow. A chromate of lead, which makes a bad pigment for oil painting. It is very poisonous and not durable; when mixed with white lead it turns to a dirty grey. As a water-colour pigment it is less objectionable. ”

“ Bunsen obtained metallic chromium by decomposing a solution of chromic chloride, Cr2Cl6, by a galvanic current, as scales of a grey colour (sp. gr. 7·3) . Wöhler obtained crystalline chromium by igniting a mixture of the anhydrous chromic chloride Cr2Cl6 (see Note 7 bis) with finely-divided zinc, and sodium and potassium chlorides, at the boiling-point of zinc. When the resultant mass has cooled the zinc may [290] be dissolved in dilute nitric acid, and grey crystalline chromium (sp. gr. 6·81) is left behind. ”

“ It has the advantage of relative cheapness, and can be conveniently obtained and introduced into glass in the form of pure compounds whose colouring effect can be accurately anticipated; the colours191 produced by the aid of chromium have the further advantage of being very constant in character, being little affected by oxidising or reducing conditions, and only very slightly by the length or temperature of the melting process. The rate of cooling, in fact, appears to be the only factor that materially affects the colours produced by compounds of chromium. ”

“ Having studied the solubility of carbon in a certain number of metals in fusion—such as aluminum, iron, manganese, chromium, uranium, silver, and platinum—and in a metalloid, silicon, he succeeded in obtaining by fusion in one of these metals new varieties of graphite; but he was able to produce crystallized carbon, or diamond, only by performing his experiments under high pressure. When iron in fusion is saturated with carbon, different results are obtained according to the temperature to which the mass is raised. ”

“ All modern armour contains nickel in percentages varying from 3 to 5, and from 1·0 to 2·0% of chromium is also employed as a general rule. Nickel in the above quantities adds greatly to the toughness as well as to the hardness of steel, while chromium enables it to absorb carbon to a greater depth during cementation, and increases its susceptibility to tempering, besides conducing to a tough fibrous condition in the body of a plate. ”

“ An alloy of chromium with carbon steel has been before the public for many years, and greater claims have been made for it than experience seems to justify. Chrome steel is fine-grained and very hard in the hardened state, and it will do a large amount of work at the first dressing; upon redressing it deteriorates much more rapidly than carbon steel and becomes inferior; it is believed that this is due to a rapid oxidation of the chromium. ”

“ A green precipitate, perhaps CrPO4·3H2O, is obtained on adding an excess of sodium phosphate to chromic chloride solution.
Carbides of chromium are known; when the metal is heated in an electric furnace with excess of carbon, crystalline, C2Cr3, is formed; this scratches quartz and topaz, and the crystals are very resistant to the action of acids ”

“ Chromium and nickel plated finishes are of a perishable nature and will deteriorate if not properly cared for. These parts should be kept clean and free from dirt and foreign matter. To clean chromium plated parts, use clear water and a clean cloth. To protect the finish after the parts are cleaned, apply a coating of paste-type body wax. For further details on chrome plated parts, see the card placed in the package compartment. ”

“ Rowland's splendid photographs of the solar spectrum have contributed most effectively. About half of these elements, though not in order of certainty, are aluminum, cadmium, calcium, carbon, chromium, cobalt, copper, hydrogen, iron, magnesium, manganese, nickel, scandium, silicon, silver, sodium, titanium, vanadium, yttrium, zinc, and zirconium. Oxygen, too, is pretty surely indicated; but certain elements abundant on earth, as nitrogen and chlorine, together with gold, mercury, phosphorus, and sulphur, are not found in the sun. ”

“ Chromium trioxide, CrO3, is obtained by adding concentrated sulphuric acid to a cold saturated solution of potassium bichromate, when it separates in long red needles; the mother liquor is drained off and the crystals are washed with concentrated nitric acid, the excess of which is removed by means of a current of dry air. ”

“ Oxide of chromium and aluminium powder are intimately mixed together in a refractory crucible, and the mixture is ignited at the upper part. The aluminium and chromium oxide react with evolution of so much heat that the reduced chromium is melted. Such is the intensity of the reaction that the resulting alumina is also completely fused, floating as a liquid on the molten chromium. Sometimes the alumina takes tip the right amount of chromium to enable it to assume the ruby colour. ”

“ Chrōmatop′sia, coloured vision; Chrō′matrope, an arrangement in a magic-lantern by which effects like those of the kaleidoscope are produced; Chrō′matype, Chrō′motype, a photographic process by which a coloured impression of a picture is obtained.—adj. relating to the chromatype.—ns. Chrōme, Chrō′mium, a metal remarkable for the beautiful colours of its compounds.—adj. Chrōm′ic.—ns. Chrō′mite, a mineral consisting of oxide of chromium and iron; Chrō′mo-lith′ograph, or merely Chrō′mo, a lithograph printed in colours ”

“ Chromium Oxide, Viridian, Emerald Green.
Chromium Oxide is, as its name implies, an oxide of chromium; this is an opaque variety. Viridian is also an oxide of chromium, but is transparent. Both these are quite permanent.
Emerald Green is aceto-arsenite of copper, and a somewhat dangerous colour to use; it is darkened by impure air, but this is not so serious as are its effects upon other colours when mixed with them. If used at all, it should be used quite by itself, as if it is mixed with129 other colours it is sure to have a bad effect on them. It turns some colours black very quickly. ”

“ The assay of the chrome ore, alluded to above, may be made by reducing 100 gr. of it to powder, mixing it with twice its weight of powdered nitre, and a little hydrate of calcium, and subjecting the mixture to a strong red heat for 3 or 4 hours; the calcined mass may then be exhausted with boiling water, and the resulting solution, after precipitation with dilute sulphuric acid, in slight excess, and filtration, may be treated with rectified spirit, when its chromium may be thrown down by the addition of ammonia. ”

“ When heated with phosphorus trichloride in a sealed tube to 160° C., potassium chlorochromate, phosphorus oxychloride, potassium chloride, and a complex chromium oxide (possibly Cr3O6) are produced (A. Michaelis, Jour. prak. Chem., 1871, ii. 4, p. 452) . Potassium bichromate finds application in photography, in calico-printing and in the preparation of bichromate cells. Sodium bichromate, Na2Cr2O7·2H2O, may be obtained by the addition of the requisite quantity of chromium trioxide to a solution of sodium chromate. ”

“ The spectra of a large number of terrestrial substances have been examined in comparison with the solar spectrum, and thus it has been established that many of the elements known on the earth are present in the sun. We may mention calcium, iron, hydrogen, sodium, carbon, nickel, magnesium, cobalt, aluminium, chromium, strontium, manganese, copper, zinc, cadmium, silver, tin, lead, potassium. Some of the elements which are of the greatest importance [Pg 51] on the earth would appear to be missing from the sun. ”

“ The chrome discharge is produced by padding the goods in chromium bisulphite; then drying them, and printing-on citric acid, or chlorate of soda and yellow prussiate of potash. They are then steamed, passed through chalk and water, well washed and dyed up in any mordant dye.
(d) Turkey red may be discharged in both white and coloured patterns by either oxidizing agents or caustic alkalis. (1) The dyed cloth is printed with strong citric acid, or arsenic acid, at 180° Tw.. and then run through bleaching powder solution, whereby the printed parts are completely decolonized. ”