CHAPTER XXII

THE INDUSTRIAL APPLICATIONS OF TITANIUM AND ITS COMPOUNDS

Though probably at least as plentiful in nature as most of the common metals, titanium has always, until quite recently, been regarded as one of the rare elements. Of its chemistry, very little indeed was known, and it is improbable, even now, that the pure element has been isolated. It had no technical value; indeed, its commonest ore, ilmenite or titaniferous iron ore, was sedulously avoided by manufacturers, who considered that even very small percentages of the element rendered an iron ore valueless because unsuitable for working in blast furnaces. Towards the end of the last century, one or two metallurgists had demonstrated that ilmenite, under the proper working conditions, would yield a pig iron of very good quality when smelted in the blast furnace, but it was left for the long and arduous researches of Kossi to show that the element is possessed of properties which render it very valuable for metallurgical purposes. Since the successful culmination of his work in the first few years of the present century, titanium has attained considerable importance in the treatment of special steels for rails, car wheels, crushing machinery, etc. At present, titaniferous iron ores are being worked on a large scale, and many titanium compounds are coming into use for technical purposes.

The titanium minerals of commercial importance are rutile and ilmenite (_vide_ Part I. pp. 57 and 77). The former, the pure titanium dioxide, is of fairly wide distribution, but ilmenite occurs in far greater quantities, forming deposits of enormous dimensions, especially in America, as, _e.g._ in New York Co. and Quebec. Owing to its high melting-point and relatively low specific gravity, metallic titanium can only be incorporated with molten steels with the greatest difficulty, and for this reason alloys of titanium and iron, known technically as ferro-titanium, are usually employed for the treatment of steels. For the preparation of ferro-titanium, ilmenite of good quality is as suitable as rutile, and, of course, far cheaper; hence the latter is only employed for the preparation of titanium salts for use in colouring and mordanting, and for titanium compounds for arc-lamp electrodes, etc.

Various processes are employed for the manufacture of ferro-titanium from ilmenite. In cases in which a considerable percentage of carbon is not undesirable, for instance, where the alloy is required for the treatment of cast iron or of high-carbon steel, the mineral is reduced directly with carbon in an electric furnace; the ferro-titanium so obtained usually contains from six to eight per cent. of carbon. For pure iron-titanium alloys, the process worked out by Rossi[609] is used in America almost entirely. Ilmenite is charged into a bath of molten aluminium, heated electrically; the mineral is at once attacked, with formation of iron, in which the titanium dissolves as reduction proceeds. This process may also be used for reduction of rutile, if scrap iron is added to the aluminium bath, to allow of the formation of the required alloy. In Germany, the Goldschmidt or ‘thermite’ reaction is largely employed; powdered ilmenite is intimately mixed with the calculated quantity of aluminium powder, reduction being started as usual by means of a fuse of magnesium ribbon imbedded in a small quantity of barium peroxide.

[609] _Elect. chem. Ind._ 1903, ~1~, 523.

Quite recently, the question of the separation of titanium compounds from ilmenite used for the manufacture of pig iron has attracted considerable attention. It has been already mentioned (_vide supra_) that titaniferous iron ores have been shown to be perfectly amenable to blast-furnace treatment, the old and deeply rooted idea that titanium-bearing slags are stiff and troublesome being entirely contrary to facts, when suitable conditions are observed;[610] moreover, it is shown that the pig iron obtained is of unusually good quality. Rossi has suggested[611] that if sufficient carbon be added to reduce all the silica and oxides of iron, with enough lime to slag off the titanium dioxide as calcium titanate, the latter can be used as a source of titanium compounds or alloys, whilst a ferro-silicon will be obtained as pig metal; the temperature must be carefully adjusted to ensure reduction of the silica without loss of titanium dioxide. Another patent[612] proposes the reduction of the ore in an electric furnace, and the treatment of the crude ferro-titanium in a converter with a blast of air or nitrogen; the titanium nitride formed is then driven out of the metal by a blast of superheated steam--any ammonia or cyanogen formed being collected--and removed, the iron remaining being ‘Bessemerised’ directly in the same converter; the titanium nitride can be used as a manure, or for the manufacture of ammonia or nitric acid (_vide infra_). The removal of iron as the volatile carbonyl has also been suggested,[613] the titanium being subsequently transformed into the nitride.

[610] _Vide_, _e.g._ _Iron Age_, 1909, ~84~, 1149 and 1223.

[611] _E._ 3582, 1901.

[612] Sinding-Larsen and Willumsen, _D. R. P._ 220544, April, 1910.

[613] Sinding-Larsen, _E._ 17632, 1910.

~Employment of the Element in Metallurgy.~--It has been already mentioned that titanium itself is quite unsuitable for direct incorporation with steel. Besides the relatively low specific gravity (5·2), which would render mixing very difficult, the very high melting-point (given by Weiss and Kayser[614] as 2350°) would prevent uniform dissemination. The element is therefore generally used in the form of a ferro-titanium of low titanium content, 10-15 per cent. being the proportion usually employed. The addition should be made at the end of the Bessemer process, and after the addition of the required quantities of manganese and silicon alloys; the calculated quantity of ferro-titanium is added as the steel runs from the converter into the ladle. A suitable proportion is said to be one-half per cent. of alloy, so that the actual proportion of titanium to steel is somewhere about 1·5-1·8 lb. per ton. Six or eight minutes should be allowed after the addition, for the titaniferous slag to come to the surface.

[614] _Zeitsch. anorg. Chem._ 1910, ~65~, 345.

Although low percentage ferro-titanium is usually employed, it has been stated that high-percentage alloys, and even the element itself, are immediately taken up by steel if aluminium be added at the same time. Thus Venator[615] states that if titanium and aluminium be added together to the bath, both elements are immediately taken up, the reaction being very rapid and complete; the effects produced by the titanium are in no way influenced by the presence of the aluminium. Goldschmidt[616] proposes the use of ferro-titanium containing 24-25 per cent. of the element, with 3 per cent. of aluminium; this dissolves very readily, is very effective, and moreover, can be very easily prepared by the alumino-thermic reaction.

[615] _Stahl Eisen_, 1910, ~30~, 650.

[616] _D. R. P._ 235461, June, 1911.

In some cases, where it is desired to treat a steel both with silicon and with titanium, ferro-alloys containing both of these elements may be employed. By reduction of ilmenite or rutile with carbon in an electric furnace, in presence of silica, Becket[617] obtains alloys of high titanium and silicon content, which are said to dissolve very easily in molten steels and to produce improved effects. The Titanium Alloy Manufacturing Company have also patented[618] the preparation of titanium-silicon alloys, with or without addition of iron or copper, by the reduction of a mixture of rutile and quartz.

[617] _U. S. P._ 940665 and 941553 of November, 1909.

[618] _F._ 407858, January, 1910.

Recently the use of ferro-titanium in the manufacture of pig iron has attracted attention. For this purpose, alloys of very low titanium-content (0·1-1·0 per cent.) are employed. Addition of very small amounts of such alloys to the molten metal before casting is said to have a marked cleansing effect,[619] resulting in much better and stronger castings.

[619] _Vide_ Slocum, _Chem. Eng._ 1911, ~13~, 257.

Whilst it is very generally agreed that the addition of titanium results in the production of much stronger and more durable products, the question of the precise effect obtained is by no means definitely settled. The experimental work, whilst pointing on the whole to the superiority of titanium-treated steel, is by no means conclusive; in some cases, indeed, it is conflicting. Thus the micro-photographs obtained by von Maltitz[620] and Venator[621] show that the titanium-treated steel has a far cleaner fracture and far more homogeneous structure than steels not so treated; on the other hand, the micro-photographs of Treuheit[622] show practically no improvement in structure for the titanium steel. The exhaustive tests of the first two authors, again, and the experiments of numerous railways in the use of titanium steel rails,[623] demonstrate clearly that the treatment results in improvement in strength and durability of the product; but the work of Otto[624] proves equally clearly that his products did not differ markedly, whether titanium-treated or not, and he is of opinion that the rail tests were not sufficiently prolonged or searching to be considered conclusive. It is nevertheless to be considered certain that the use of titanium does cause a marked improvement in the quality of the steels obtained, and especially in the durability of rails. The negative results obtained by some authors may be explained, firstly, on the ground that no tests are conclusive unless carried out with steel from the one bath, one half of which has been treated with titanium, and the other half not so treated; secondly, that the ferro-titanium must be incorporated with the metal, and must not be suffered to be taken up by the slag, and so lost; and thirdly, that the bath must be allowed to remain for some minutes after treatment, in order that the reaction may be complete, and the titanium-bearing slag allowed to rise to the surface. When these conditions are carefully observed, experiment shows that marked improvement in the quality of the steels produced is effected.

[620] _Stahl Eisen_, 1910, ~29~, 1593.

[621] _Ibid._ 1910, ~30~, 650.

[622] _Ibid._ 1910, ~30~, 1192.

[623] _Vide_ Dudley, _J. Ind. Eng. Chem._ 1910, ~2~, 299; also _Cass. Mag._ 1911, ~40~, 483.

[624] _Vide_ abstract in _Stahl Eisen_, 1912, ~32~, 1497.

As to the actual nature of the effect produced, it is generally believed that titanium acts merely as a cleansing agent, freeing the metal from occluded or combined gases, and removing blow-holes, so producing a denser and more homogeneous structure, with consequent improvement in properties. The added titanium is usually found entirely in the slag, so that it appears certain that it does not alloy, but merely purifies. It certainly acts as a powerful and rapid deoxidiser, removing the last traces of the gas which have escaped the action of the manganese, silicon, etc., with which steels are now generally treated. Many authorities, on the ground of analyses, and of the known affinity of titanium for nitrogen, believe that it very largely reduces the nitrogen-content,[625] which is so harmful; this, however, is still an open question.[626] It is stated that if excess of titanium is used, so that small quantities--0·05-0·20 per cent.--remain in the finished steel, the toughness and durability are further increased;[627] but as a rule, manufacturers prefer to work with smaller quantities, so that no free titanium remains in the product.

[625] _Vide_ von Maltitz, _loc. cit._

[626] _Vide_ Venator, _loc. cit._

[627] _Vide_ _Bull. Imp. Inst._ 1911, ~9~, 134.

* * * * *

The preparation of alloys of titanium with almost all the commoner metals is protected by patent, but few of these are of technical importance. Small quantities of titanium are said to improve very considerably the properties of copper and its alloys, the brasses, bronzes, etc., especially in castings. The addition is usually made in the form of an appropriate titanium alloy, prepared by reduction of the mixed oxides with carbon in an electric furnace, or treatment of the mixed oxides, together with the alloying metal, with aluminium under similar conditions.[628] The titanium-silver alloys obtained in this way[629] are said to improve greatly the structure of silver, by preventing the familiar ‘spitting’ as the fused metal cools.

[628] _Vide_ Rossi, _U. S. P._ 986505, March, 1911; 935863, October, 1909, etc.

[629] Rossi, _U. S. P._ 1024476 and 1025426, August, 1912.

An interesting process, which has been patented by Rossi,[630] recalls the method of formation of cementation steels. He has found that if a metal be loosely covered with its alloy with titanium, in a finely powdered condition, and the whole heated, the titanium diffuses into the metal, to a depth and concentration which vary with the temperature and the time of heating. He suggests that in this way a metallic body may be toughened and strengthened at any desired point, _e.g._ steel for armour-plate at the surface. Whether the process will be of any technical value or not can only be shown by experiment.

[630] _U. S. P._ 986504, March, 1911.

~Application to Arc-lamp Electrodes.~--During the last fifteen years, innumerable efforts have been made to adapt titanium and its compounds to the manufacture of arc-lamp electrodes, or pencils.[631] The spark-spectrum of titanium is very rich in lines, and in respect of light efficiency, the element is very suitable for the purpose; the experimental difficulties, however, have been very great, and though electrodes containing titanium compounds have been on the market for some years, the problem cannot be said to have been satisfactorily solved. The best pencils contain titanium carbide, but successful attempts have been made to use the oxide. As early as 1904, Weedon[632] proposed an electrode prepared by heating 7 parts (1 mol.) of the dioxide with 1 part of carbon to 1500°-2000°C.; the ‘sub-oxide’ produced was powdered, worked up into a paste with a suitable binding material, and forced through a nozzle. The sticks so obtained, after drying and baking in the usual manner, were said to give satisfactory results, but consumption is very rapid, and troublesome deposits of the dioxide are formed at the end of the electrode. The dioxide, which alone is a very bad conductor, enters directly into the composition of the so-called ‘magnetite’ pencils, which are best made[633] by fusing together magnetite, rutile, and chromite, in suitable proportions, with a little potassium fluoride, powdering the brittle mass, and using this to form a paste from which the pencils may be obtained as usual. These electrodes are said to give a very efficient and fairly steady arc. They have the disadvantage that tiny glowing particles are thrown off, which soon render the globes opaque; the addition of sulphur[634] to the powder during manufacture is said greatly to diminish this inconvenience. Pencils made in a similar manner from powdered ferro-titanium[635] do not appear to have come into use.

[631] _Vide_, _e.g._ Ladoff, _J. Ind. Eng. Chem._ 1909, ~1~, 711.

[632] _E._ 26921, 1904.

[633] _E._ 2027, 1909.

[634] _E._ 18965, 1909.

[635] _U. S. P._ 840634, January, 1907.

The carbide alone is a good conductor, and gives a very satisfactory light,[636] but electrodes made from this compound without additions have several disadvantages. The life is short, and the arc soon becomes flickering and unsteady. A deposit of the badly conducting dioxide gradually accumulates on the anode, and once the current has been interrupted, this deposit renders it very difficult to strike the arc again. These disadvantages are largely overcome by a series of improvements recently patented in Germany by the Allgemeine Elektrizitäts Gesellschaft of Berlin. Addition of small quantities--4·5 per cent.--of chromium carbide increases the length of life;[637] the unsteadiness and flickering are greatly diminished by incorporation of powdered coke, cryolite and fluorspar,[638] or better, of the titanofluoride of calcium or cerium,[639] whilst the addition of finely divided sulphur (or selenium or tellurium)[640] greatly reduces the disadvantage due to the throwing off of incandescent particles. The British Thomson-Houston Company patents a similar electrode,[641] in which a carbon-mixture is used instead of coke, and the electrode is manufactured with a carbon shell. For this purpose, the paste prepared from the powdered mixture may be filled into a hollow carbon rod, or the lightly baked pencil may be coated with pitch and heated to a high temperature. The use of a mixture of cerium fluoride and tungstate, with carbon and cryolite, is also said to prevent flickering.[642]

[636] Weedon, _Trans. Amer. El. chem. Soc._ 1911, ~16~, 217.

[637] _D. R. P._ 231231, February, 1911.

[638] _Ibid._ 233125, March, 1911.

[639] _Ibid._ 251837, October, 1912.

[640] _Ibid._ 234466, May, 1911.

[641] _E._ 6500, 1912.

[642] Guay, _U. S. P._ 1039522, September, 1912.

In arc lamps in which pencils containing titanium compounds are used, the anode is generally made of copper, and is placed below the cathode, the reverse being the case where carbon electrodes are employed. The copper is inactive, and contributes nothing to the light; if the anode be of suitable dimensions, it wears away very slowly, whereas the cathode, containing the titanium compound, is rapidly consumed. In lamps in which carbon electrodes are used, the light is emitted chiefly from the extremities of the electrodes, the path of the arc being comparatively non-luminous; the light has the familiar reddish-yellow colour characteristic of the earlier forms of arc lamps. Where titanium pencils are employed, however, the light is emitted almost entirely from the arc itself, the electrodes contributing very little, and is of a pure white colour, very different from that of the carbon lamp.

Attempts have been made to employ titanium in the manufacture of metal filaments for glow lamps. The metal would be very suitable for this purpose, by reason of its high melting-point and low conductivity, but the difficulty of obtaining it in the pure state, and the remarkable susceptibility of the filament to traces of impurity, have so far proved insuperable. For the sake of illustration, a proposal put forward in 1908 may be briefly referred to.[643] Pure titanium dioxide is heated in a stream of ammonia; the nitride obtained is decomposed at 1200° _in vacuo_, and after cooling, the metal is powdered and made into a paste with a solution of albumen in ammonia. The threads obtained from this in the usual manner are heated to 1200° in an electric furnace; the carbon deposited from the albumen forms the cyanide by reaction with the trace of nitride which has escaped decomposition, or which has been formed by further action of ammonia. The cyanide is volatile, and can be removed at high temperatures _in vacuo_, leaving a sintered filament of the metal. So susceptible is the filament to impurity, that the trace of carbon deposited from the vapour of the oil of the pump which diffuses into the vacuum is sufficient to render it so fragile as to be useless.[644]

[643] Trenzen and Pope, _E._ 14852, 1908.

[644] _Vide_ _Bull. Imp. Inst._ 1911, ~9~, 134.

~Titanium Compounds in Dyeing and Colouring.~--The use of titanium compounds as mordants in the dyeing of leather and textile goods has been known for a considerable time.[645] As early as 1896, a patent was taken out by Barnes[646] for the treatment of prepared animal skins by immersion in a bath of a titanium salt. Subsequent boiling or steaming causes hydrolysis, with precipitation in the skin of hydrated titanium dioxide, which forms lasting dye-lakes when the fabric is immersed in the dye-bath. Whilst this treatment has been found satisfactory with some classes of leather goods,[647] more delicate kinds are liable to be injured by the mineral acid set free, and numerous patents protecting the preparation and employment of organic salts of the element have been taken out by Dreher.[648] The same investigator[649] has discovered that excellent results can be obtained in the cold by the addition of various ‘Hülfsalze,’ which are chiefly acetates or formates of the alkaline earth metals, chromium, or aluminium, or basic salts of the last two. Double decomposition of these with the titanium salt forms basic or highly hydrolysed salts of the latter, so that the hydrated oxide or a basic compound is formed on the fabric.

[645] A good account of some of the earlier work in this connection is given by Erban, _Chem. Zeitg._ 1906, ~30~, 145.

[646] _E._ 5712, 1896.

[647] _Vide_ Dreher, _D. R. P._ 142464, June, 1903.

[648] _Vide_ _E._ 22629 and 23188 of 1901, 14921 and 27597 of 1902, and 5211 of 1903.

[649] _Vide_ _D. R. P._ 139059 and 139060 of February, 1903, and 139838 of March, 1903.

The titanium salts specified in these patents are salts of the element in the tetravalent condition, prepared from rutile by the action of strong mineral acids. As early as 1902, the technical preparation of salts of trivalent titanium for reducing purposes was patented by Spence and Spence, of Manchester.[650] The process is an electrolytic one, and is effected in a cell divided into two compartments by a porous partition, one electrode being introduced into each compartment; an electromotive force of 3-4 volts is required. A 20-25 per cent. titanium tetrachloride solution is introduced into the cathode compartment, and dilute hydrochloric acid into the anode compartment; on electrolysing, chlorine is evolved at the anode, and may be utilised as usual in the preparation of bleaching powder, etc., whilst the tetrachloride in the cathode compartment is reduced to trichloride. The solution is then concentrated at 65°-70°C. under reduced pressure, and the crystalline trichloride separated. In the preparation of the corresponding sulphate, sodium sulphate must be present in the cathode compartment, and a double salt is obtained; the process is carried out in lead-lined cells, in presence of excess of sulphuric acid. The preparation of the sesquioxide, Ti₂O₃, free from compounds of aluminium and iron, was also suggested by Dreher[651] by reduction of the acid solution of the impure or mixed salts with zinc or sodium amalgam, and approximate neutralisation; the sesquioxide differs from the dioxide in that it separates while the solution is still somewhat acid, which the hydrated oxides of iron and aluminium will not do. Dreher suggested that the strong reducing properties of the sesquioxide and its salts should make these valuable for bleaching, colour-printing, and similar purposes.

[650] _E._ 16238 and 18108 of 1902.

[651] _E._ 1835, 1903.

More recently[652] the reduction of titanium salts by means of aluminium powder has been suggested; in the case of the sulphate, the aluminium salt formed may be partly eliminated as alum, in the ordinary way, if desired, but it is claimed that its effect is beneficial rather than harmful. The preparation of organic double basic salts of trivalent titanium,[653] which hydrolyse very readily, suggested the use of such compounds as mordants and for reducing purposes. These salts may be prepared fairly easily[654] by adding concentrated solutions of the appropriate potassium, sodium, or ammonium salts in excess to concentrated solutions of the trichloride, in absence of air. The double salts separate, and are washed and dried; in this condition they are fairly stable, but the solutions hydrolyse at once on merely warming, with separation of the hydrated sesquioxide. On this account, and also because of the strong reducing action, these compounds are likely to prove valuable as mordants, and for other purposes.

[652] Spence, Craig, and Spence, _E._ 13260, 1911.

[653] Stähler and Bachran, _Ber._ 1911, ~44~, 2912.

[654] Kunheim and Co. and Stähler, _D. R. P._ 284251, June, 1912.

Titanium compounds have frequently been suggested for the preparation of colouring-matters; the ferrocyanide has a fine green colour, and is used to some extent in place of arsenical pigments for the preparation of coloured wall-papers, whilst the dioxide is of some value for tinting artificial teeth, porcelain tiles, etc. Yellow and reddish-yellow pigments are produced from rutile and ilmenite by various methods. A fine covering paint is said to be obtained by a process[655] in which ilmenite is powdered and roasted to 500°C.; the cooled product is crushed with water, and after one or two washings to remove soluble compounds, yields a very finely divided orange-yellow suspension, the precise shade of which varies with the duration and temperature of the roasting. The product is at once thrown down from the suspension, by addition of a small quantity of a salt solution, and so can easily be obtained in the solid state. In another process,[656] the pulverised ilmenite is warmed with concentrated sulphuric acid, in which it dissolves with great development of heat; the excess of acid is removed by evaporation and the mass calcined to decompose the sulphates. It is stated that different shades may be obtained by carrying out the last operation in an atmosphere of sulphur dioxide or other gas.

[655] Farup, _E._ 3649, 1910; _F._ 412563, May, 1910.

[656] _E._ 10368, 1911.

In connection with the colouring properties of the oxides of titanium, it is interesting to note that the blue colour of sapphires is probably due to the presence of compounds of trivalent titanium; Verneuil[657] has succeeded in preparing artificial sapphires in all respects identical with the natural stones by fusing alumina with small quantities of titanium dioxide and ferric oxide in the flame of the oxyhydrogen blowpipe, which effects the reduction.

[657] _Compt. rend._ 1910, ~150~, 185.

~Other Uses of Titanium Compounds.~--Owing to the high price of the tin dioxide which is largely employed for the preparation of enamels and opaque glasses, innumerable suggestions have been made for the employment of the oxides of titanium and zirconium in this direction.[658] A critical examination of the question has been made by Grünwald;[659] he finds that the opacity consequent on addition of these compounds increases with the amount of clay used, within limits, and concludes that the effect is due to displacement of alumina by the oxides, with formation of silicates of titanium and zirconium, which dissolve in the melt. He states that the results obtained from the use of these oxides are not comparable with those given when stannic oxide is employed, and that therefore the former oxides are of little use for this purpose.

[658] _Vide_, _e.g._ _D. R. P._ 189364, 218316, 115016, 207001; _F._ 438908, etc.

[659] _Sprechsaal_, 1911, ~44~, 72.

These two oxides find employment to a small extent in the manufacture of ‘Siloxide’ quartz glass.[660] Quantities up to 1·5 per cent., added to the molten silica, reduce the difficulty of working the material. Exhaustive tests carried out by Thomas[661] indicate that the vessels made from this material are, on the whole, to be preferred to ordinary quartz glass, resisting high temperature better, and showing less tendency to become crystalline and therefore brittle when maintained for considerable times at high temperature.

[660] Wolf-Burckhardt and Borchers, _F._ 432786, October, 1911.

[661] _Chem. Zeitg._ 1912, ~86~, 25.

* * * * *

Much work has been carried out during the last few years with the object of utilising titanium compounds for the ‘fixation’ of nitrogen.

The metal combines very vigorously with the gas at about 800°C. (_vide_ p. 224), forming the nitride. If the gas, or air, be passed over a heated mixture of the dioxide with powdered coke, formation of the cyanonitride occurs at comparatively low temperatures (1100°-1300°C.) if a small quantity of an alkali salt be present,[662] the action being apparently catalytic; if excess of carbon is used, considerable quantities of the cyanide may be formed. Numerous experiments carried out by the chemists of the Badische Anilin- und Soda-Fabrik have shown that at high temperatures, the action of water and a suitable oxidising agent, or in the presence of metallic compounds, the action of steam alone, will liberate considerable quantities of ammonia from both these derivatives,[663] whilst in the presence of platinum compounds, if air be pumped in, the higher oxides of nitrogen are formed. One or two examples may be given:

(1) Ti₂N₂ + 4NaOH + H₂O + 2CuO = 2NH₃ + Cu₂O + 2Na₂TiO₃--autoclave at 180°C.

(2) 2Ti₂N₂ + 2H₂SO₄ + 6H₂O + O₂ = 4TiO₂ + 2(NH₄)₂SO₄--autoclave at 120°-140°C.

(3) Ti₂N₂ + 3H₂O = Ti₂O₃ + 2NH₃--steam at 500°-600°C.

[662] _Vide_ Bosch, _U. S. P._ 957842, May, 1910.

[663] _Vide_, _e.g._ _D. R. P._ 202563 and 203748 of March, 1907; 204204 and 204475 of November, 1908; _E._ 2414, 1908; _F._ 387002 of June, 1908; _U. S. P._ 957843 of May, 1910, gives a résumé of all the processes.

In the second case, the oxygen is derived from air pumped into the apparatus, and ferrous sulphate is used as a catalyst. In the third case, a metallic salt, oxide, or hydroxide is required as a catalyst.

In view of the success of the cyanamide method for the fixation of atmospheric nitrogen, these processes, though of considerable theoretical interest, do not seem likely to become of practical importance.

* * * * *

One or two minor uses have been suggested for titanium dioxide. Small quantities are fused with bauxite, silica, and ferric oxide in the preparation of abrasives,[664] whilst a mixture with carbon is suggested as a refractory body for linings, crucibles, etc., surface heating of this forming a layer of highly resistant carbide.[665] An interesting American patent protects the use of the dioxide for the preparation of phosphorus pentoxide from bone-ash or natural calcium phosphate.[666] The pulverised mixture of the phosphate and oxide is introduced at the upper end of an inclined rotating furnace, by means of a hopper and screw feed; fuel is fed in at the lower end, and an outlet is provided for the periodic removal of the calcium titanate, etc., formed. The silica and alumina of the impure phosphate, together with the titanium dioxide introduced, displace the phosphorus pentoxide, which, being volatile, escapes continuously through a special pipe; there is left a mixture of silicate, aluminate and titanate of calcium, which may be used as a source of titanium compounds.

[664] Saunders, _U. S. P._ 954766, 954777, and 954778.

[665] Becket, _U. S. P._ 1038827, September, 1912.

[666] Peacock, _U. S. P._ 995897, June, 1911.

~Estimation of the Element.~--Owing to the difficulties of the separation from the acidic oxides, silica, zirconia, and the pentoxides of columbium and tantalum, and from the basic oxides, alumina and the oxides of iron and tin, the estimation of titanium in a mineral or a steel is usually a difficult and tedious process. Gravimetric as well as volumetric methods are employed. In the former, the element is isolated and weighed in the form of the dioxide; in the latter, standard solutions of suitable oxidising agents are employed, advantage being taken of the ease with which the element can be transformed from the trivalent to the tetravalent condition.

The mineral or steel in which the element is to be estimated is usually fused with sodium hydrogen sulphate, which forms the sulphate. If thorium, uranium or rare earths are present, treatment in the cold with hydrofluoric acid is often more suitable; the acidic oxides are taken into solution, leaving the more positive elements in the form of the insoluble fluorides. Trautmann finds that steels or ferro-titaniums of high silicon content are attacked only very slightly by fused sodium bisulphate; he recommends[667] ignition to the oxides, evaporation with hydrofluoric acid to remove silicon as the volatile tetrafluoride, and fusion of the residue with bisulphate.

[667] _Zeitsch. angew. Chem._ 1911, ~24~, 877.

The bisulphate melt, after cooling, is leached with water, and the whole boiled under a reflux condenser for several hours; this treatment should throw down the oxides of titanium, columbium and tantalum, leaving zirconium and aluminium in the form of the sulphates in the acid solution; the addition of ammonia may be necessary to effect complete hydrolysis. The acidic oxides may also be precipitated if the solution be diluted and treated with excess of acetic acid before boiling. In both cases, a considerable quantity of iron is thrown down. The precipitated oxides are dissolved in the cold by dilute sulphuric acid to which hydrogen peroxide has been added.

For volumetric estimation, separation from iron is not generally necessary. If gravimetric methods are to be employed, separation may be effected in several ways. Titanium dioxide may be precipitated in a fairly pure condition by reducing the solution with sulphur dioxide, and boiling until the titanium sulphate has been completely hydrolysed. According to Barneby and Isham,[668] this method gives low results; these authors prefer to remove iron completely from the solution, and then effect complete hydrolysis by addition of ammonium acetate and acetic acid to the boiling solution. For this purpose, they dissolve the mixed oxides in hydrochloric acid, and remove ferric chloride by ether extraction. Bornemann and Schirmeister[669] precipitate titanium dioxide completely by means of ammonia, holding iron in solution as ferrocyanide; for this purpose, iron is completely reduced to the ferrous state by means of sodium hydrogen sulphite, and solutions of potassium cyanide and ammonia are added together to the warm liquid, which is afterwards heated nearly to the boiling-point to effect the precipitation.

[668] _J. Amer. Chem. Soc._ 1910, ~32~, 957.

[669] _Metallurgie_, 1910, ~7~, 723.

Iron may also be removed by the ordinary methods, if some reagent be previously added to hold titanium in solution. For this purpose, tartaric acid and its salts are commonly used; none of the ordinary precipitants will throw down the element if this reagent be present. After addition of ammonium tartrate, iron is removed by means of ammonium sulphide. After filtering, tartaric acid may be removed by means of potassium permanganate, the manganese dioxide formed being reduced with sulphur dioxide. According to Thornton,[670] evaporation with a mixture of sulphuric and nitric acids is a more convenient method of destroying the organic acid; titanium dioxide is then thrown down by diluting and boiling in the usual way.

[670] _Amer. J. Sci._ [iv.], 1912, ~34~, 214.

Bourion[671] describes a method of separating the oxides by the action of a mixture of hydrogen chloride and sulphur monochloride at a suitable temperature. The ferric chloride which is formed sublimes, leaving titanium dioxide unattacked.

[671] _Compt. rend._ 1912, ~154~, 1229.

For volumetric estimation of small quantities of titanium in solution, colorimetric methods are generally employed. Addition of hydrogen peroxide to such a solution gives an intense reddish-yellow colouration, which is compared with the colourations obtained with solutions containing known quantities of the element. Wells[672] finds that under suitable conditions, an accuracy of about 2 per cent. is to be expected with this method. Lehner and Crawford[673] find that in concentrated sulphuric acid solution, thymol gives a red colouration which is at least twenty-five times as intense as the colour given by hydrogen peroxide, and they accordingly propose thymol as a suitable reagent for the colorimetric estimation. Fenton[674] has shown that a very intense colouration is obtained when a solution of a titanium salt is treated with dihydroxymaleic acid; this reaction has been shown by Mellor[675] to be well adapted for the colorimetric estimation and for the estimation of titanium and vanadium together in a solution.

[672] _Zeitsch. anorg. Chem._ 1911, ~70~, 395.

[673] _J. Soc. Chem. Ind._ 1912, ~31~, 956.

[674] _Trans. Chem. Soc._ 1908, ~93~, 1064.

[675] _Abstr. Chem. Soc._ 1913, ~104~, ii. 627.

The volumetric methods for the estimation of larger quantities require complete reduction to the trivalent condition. This is best effected by means of zinc and hydrochloric acid, or, where potassium permanganate is to be used, by zinc and sulphuric acid. Precautions must be taken to ensure that reduction is complete; an apparatus suitable for rapid estimations has recently been described by Shimer and Shimer.[676] Where potassium permanganate is employed (Pisani’s method), the iron must be estimated separately by means of a standard solution of titanium trichloride. Knecht and Hibbert[677] titrate directly, after reduction, with a standard solution of a ferric salt, using potassium thiocyanate as indicator; here no correction has to be applied for iron originally present in the solution. The same advantage attaches also to the method of titration by means of methylene blue,[678] a dye reduced to the colourless leuco-base by salts of trivalent titanium, but not affected by ferrous salts.

[676] _J. Soc. Chem. Ind._ 1912, ~31~, 955.

[677] _Ber._ 1903, ~36~, 1549.

[678] See Hibbert, _J. Soc. Chem. Ind._ 1909, ~28~, 190.

INDEX

Absorption Spectra, ~148~

Acetate process, ~304~

Acetylacetone derivatives, ~135~

Actinium, 100

Aenigmatite, 8, 55

Aeschynite, 8, ~65~

Aldebaranium, 205

Allanite, 8, 36, ~39~, 91

Alshedite, 54

Alvite, 8, 59

Anatase, 8, ~78~

Ancylite, 8, 81

Anderbergite, 8, 49

Annerödite, 9, 61

Arc spectra, ~151~

Arfvedsonite, 9, 51

Arizonite, 9, 59

Arrhenite, 9, 70

Astrophyllite, 9, 55

Auer mantles, history of, ~270~

Auerbachite, 9, 31

Auerlite, 9, 51

Baddeleyite, 10, ~75~

Bagrationite, 10, 45

Bastnäsite, 10, 81

Beckelite, 10, 51

Benitoite, 10, 55

Beryl, 102

Blomstrandine, 10, ~68~

Blomstrandite, 10, 71

Bodenite, 11, 42, 45

Bragite, 63

Brasilite, 76

Britholite, 11, 51

Bröggerite, 11, 73

Brookite, 11, ~79~

Bucklandite, 42

Calciothorite, 11, 49

Calcite, 2, 38

Cappelenite, 11, 51

Carbides of rare earth group, ~120~

Carbonates of rare earth group, ~130~

Caryocerite, 12, 51

Cassiopeium, 205

Cassiterite, 3, 45, 46, 77

Castelnaudite, 12, 88

Cataplejite, 12, 51

Cathode luminescence, ~151~

Celtium, ~207~

Ceria, 111, 117, 118, ~161~

Ceric compounds, ~160~

Cerite, 1, ~30~

Cerium, atomic weight of, ~164~ compounds, applications of, ~317~ detection of, ~165~ estimation of, ~166~ group, history of, ~168~ separation of, ~169~ intermediate oxide of, 162 metallic, ~115~ nitrate, extraction from monazite of, ~284~ separation of, ~156~

Cerous compounds, ~158~

Chalcolamprite, 12, 70

Chardonnet process, ~302~

Chlorides of rare earth group, ~121~

Chromates of rare earth group, ~129~

Churchite, 12, 80

Clamond mantles, ~268~

Cleveite, 13, 73

Cordylite, 13, ~80~

Cossyrite, 13

Cryptolite, ~84~

Cuprammonium process, ~303~

Crytolite, 13, 49

Davidite, 13, 59

Delorenzite, 13, ~56~

Derbylite, 13, ~59~

Drummond light, ~267~

Dysanalyte, 14, 71

Dysprosium, ~199~ history of, 195 separation of, 196

Edwardsite, 84

Elpidite, 14, 45

Endeiolite, 14, 70

Equivalent weight determination, ~153~

Erbium, atomic weight of, ~202~ detection of, ~203~ group, 199 history of, 194, ~201~ salts of, ~202~ separation of, 196

Erdmannite, 14, 45

Eremite, 84

Erikite, 14, 51

Ethylsulphates of rare earth group, ~127~

Eucolyte, 14, ~50~

Eucolyte-Titanite, 54

Eucrasite, 15, 49

Eudialite, 15, ~50~

Europium, atomic weight of, 188 compounds of, ~188~ history of, 185

Euxenite, 15, 66, ~68~

Eytlandite, 60

Fahnehjelm mantles, ~269~

Fergusonite, 15, 38, ~63~, 90

Ferrocyanides of rare earth group, ~123~

Ferro-titanium, ~326~

Florencite, 15, 51

Fluocerite, 15, 89

Fluorides of rare earth group, ~120~

Fluorspar, 2, 89, 102

Formates of rare earth group, ~133~

Freyalite, 16, 49

Gadolinite, 1, 16, ~33~, 91

Gadolinium, atomic weight of, 190 compounds of, ~190~ detection of, 191 history of, 184, ~189~

Geikielite, 16, 59

Gorceixite, 16, 88

Greenovite, 54

Gröthite, 26, 54

Guarinite, 16, 51

Gummite, 73

Hainite, 16, 70

Halogen oxy-salts of rare earth group, ~123~

Harmatite, 10, 81

Helium ratio, 104, ~106~

Hellandite, 16, ~42~

Hiortdahlite, 17, ~51~

Hjelmite, 17, 64

Holmium, compounds of, ~201~ history of, ~195~ separation of, 196

Homilite, 17, 51

Hussakite, 17, 87

Hydrides of rare earth groups, ~116~

Hydrotitanite, 17, 59

Hydroxides of rare earth groups, ~116~

Illuminating power of gas, 266 of mantles, ~294~

Ilmenite, 17, ~57~, 90

Ilmenorutile, 17, 71

Johnstrupite, 17, 55

Kainosite, 18, 45

Karyocerite, 12

Kataplejite, 12, 51

Keilhauite, 18, ~52~

Kischtimite, 18, ~81~

Knopite, 18, 59

Kochelite, 18, 64

Koppite, 18, 64

Lanthanite, 18, ~79~

Lanthanum, atomic weight of, ~173~ compounds of, ~172~ detection of, 173 metallic, ~115~, 171 separation of, ~170~

Lavenite, 19, 51

Lead, 105, ~107~

Lederite, 54

Leucosphenite, 19, 55

Leucoxene, 55

Lewisite, 19, 59

Lighting devices, ~315~

Ligurite, 54

Loranskite, 19, 64

Lorenzenite, 19, 55

Lutecium, ~205~

Mackintoshite, 19, 79

Magnetic susceptibility, ~152~

Malacone, 19, 49

Mauzeliite, 20, 59

Melanocerite, 20, 51

Menaccannite, ~57~

Mengite, 84

Mesothorium, ~252~, 276

Metals of rare earth group, ~114~

Michaelsonite, ~14~

Microlite, 20, 64

Misch metal, ~115~, ~315~

Molengraafite, 20, 55

Monazite, 4, 20, ~82~ sands, 83, ~90~ technical treatment of, ~276~

Mosandrite, 20, 55

Muromontite, 20, 42, 45

Naegite, 31, 45, ~49~

Narsarsukite, 21, 55

Neodymium, atomic weight of, ~179~ detection of, ~180~ metallic, 115, 177 oxides, ~177~ salts, ~178~

Neoytterbium, 206

Neptunite, 21, 55

Nernst lamp, ~320~

Nitrates of rare earth group, ~128~

Nitrides of rare earth group, ~116~

Nivenite, 21, 73

Nohlite, 21, 64

Octahedrite, 8, ~78~

Oerstedite, 21, ~49~

Oisanite, 78

Orangite, 21, ~45~

Organic salts of rare earth group, ~133~

Orthite, 8, ~39~

Oxalates of rare earth group, ~131~

Oxides of rare earth group, 115, ~117~

Parisite, 21, ~80~

Pauly process, ~303~

Perovskite, 14, 22, 59

Peroxides of rare earth group, ~117~

Pertitanates, ~235~

Phosphates of rare earth group, ~129~

Phthalates of rare earth group, ~134~

Picroilmenite, 16, ~59~

Pictite, 54

Pilbarite, 22, ~49~

Pitchblende, 22, ~72~

Platinocyanides of rare earth group, ~123~

Platinum mantles, ~268~

Plumboniobite, 22, ~62~

Polonium, 99

Polycrase, 22, ~66~

Praseodymium-- atomic weight of, ~175~ compounds of, ~174~ detection of, 176 history of, 168 metallic, ~115~, 174 separation of, ~170~

Priorite, 22, ~66~

Pseudobrookite, 22, 59

Pyrochlore, 23, 71

Pyromorphite, 101

Pyrophanite, 23, 59

Pyrophoric alloys, ~314~

Radioactivity, ~99~

Radiothorium, 74, 99, ~253~

Ramie, mantles of, ~291~

Rare earth mixtures, examination of, ~147~

Rare earths-- extraction of, from minerals, ~147~ and periodic classification, ~135~

Retzian, 23, 88

Rhabdophane, 23, 88

Rhönite, 23, 55

Rinkite, 23, 55

Risörite, 23, 38, ~69~, 102

Rogersite, 24, 64

Rosenbuschite, 24, 55

Rowlandite, 24, 55

Rutile, 24, 45, ~77~, 90

Samarium, atomic weight of, 182 detection of, 183 history of, ~168~ metallic, ~115~, 181 salts of, ~182~ separation of, ~171~

Samarskite, 24, 38, ~60~, 91

Scandium, atomic weight of, ~217~ chemical relations of, ~214~ compounds of, ~215~ detection of, ~218~ history of, 194, ~213~ occurrence of, ~3~ separation of, ~186~

Schorlomite, 24, 55

Scovillite, 23, 88

Selenates of rare earth group, ~128~

Selenites of rare earth group, ~128~

Semelene, 54

Senaite, 24, 59

Silicofluorides of rare earth group, ~121~

Sipylite, 24, 39, ~63~

Spark spectra, ~150~

Sphene, 26, ~52~, 90, 107

Steenstrupine, 25, 51

Strüverite, 25, 71

Sulphates of rare earth group, ~124~

Sulphides of rare earth group, ~119~

Sulphites of rare earth group, ~127~

Synchisite, ~81~

Tachyaphaltite, 25, 49

Tautolite, 42

Tengerite, 25, 81

Terbium, atomic weight of, ~192~ detection of, 193 group, chemical relations of, ~185~ history of, ~184~ separation of, ~186~ history of, ~184~, 191 salts of, 192

Thalénite, 25, ~43~, 102

Thiosulphates of rare earth group, ~127~

Thorianite, 25, ~73~, 107, 251

Thorite, 25, ~45~, 108, 251

Thorium, atomic weight of, ~262~ chemical relations of, ~251~ compounds of, ~254~ detection of, ~263~ estimation of, ~285~ extraction of, 251, ~275~, 283 group relations of, ~220~ metallic, ~253~ radiochemistry of, ~252~ separation of, ~277~ sulphate purification of, ~279~

Thorogummite, 26, 49

Thortveitite, 26, ~44~

Thulium, history of, ~194~, 203 individuality of, ~204~ salts of, ~204~ separation of, 196

Titanates, ~234~

Titaniferous ironstone, ~57~

Titanite, 26, ~52~, 90

Titanium, atomic weight of, ~236~ compounds for fixation of nitrogen, ~337~ compounds of, in dyeing, ~333~ compounds of divalent, ~225~ compounds of trivalent, ~226~ compounds of tetravalent, ~230~ cyanonitride, ~224~ detection of, ~236~ electrodes, ~331~ estimation of, ~338~ group relations of, ~219~ metallic, ~223~ occurrence and extraction of, ~222~ olivine, 26, 55 steels, ~329~ uses of, in metallurgy, ~327~, ~330~

Tritomite, 26, 51

Tscheffkinite, 26, 55

Tungsten, 1, 31

Turnerite, 83

Tyrite, 63

Tysonite, 26, 89

Uhligite, 27, 59

Uraninite, 29, ~52~

Uranosphærite, 73

Urano-tantalite, 60

Vasite, 42

Vietenghfiote, 27, 64

Viscose process, ~304~

Warwickite, 27, 59

Weibyite, 27, 81

Wiikite, 27, ~70~

Wöhlerite, 28, 70

Wolframite, 2, ~214~

Xenotime, 28, 45, ~86~, 90, 207

Ytterbia, 1, 206

Ytterbite, 1, 33

Ytterbium, atomic weight of, 206 detection of, 207 history of, ~194~, 205 salts of, ~206~ separation of, 196, ~205~

Yttria, 1, 35, ~111~, 209

Yttrialite, 28, ~34~, 45

Yttrium, atomic weight of, ~211~ detection of, ~212~ group, history of, ~194~ separation of, ~195~ history of, 194, ~208~ salts of, ~210~ separation of, ~196~, 205

Yttrocerite, 28, ~88~

Ythrocrasite, 28, 56

Ythrofluirite, 28, ~89~

Yttrofluorite, 28, ~89~

Yttrogarnet, 28, 45

Yttrogummite, 28, 49

Yttroilmenite, 60

Yttrotantalite, 29, 62

Yttrotitanite, 18, ~52~

Zircon, 29, 38, 45, ~47~, 90, 107

Zirconia, uses of, ~323~

Zirconium, atomic weight of, ~249~ compounds of, ~249~ detection of, ~242~ estimation of, ~250~ extraction of, ~239~ group, relations of, ~219~, 240 history of, ~238~ industrial applications of, ~321~

Zirkelite, 29, 79

PRINTED BY SPOTTISWOODE AND CO. LTD., COLCHESTER LONDON AND ETON

Transcriber’s Notes

Inconsistent and unusual spelling and hyphenation (including those of proper and geographical names) have been retained, except as mentioned below.

Depending on the hard- and software used and their settings, not all elements may display as intended.

Lists of elements were printed both with and without separating commas (for example, R´´ = Ca, Fe´´, Be and R´ = NH₄,K,Rb,Cs); these have not been standardised.

Pages 34, weighing 200 lb.: later (page 41) referred to as weighing 300 lb.

Some tables appear to use nm, others Å; this has not been standardised.

Page 181, table: 5923·35 may be an error; it is out of sequence.

Page 200, table: 379·5 may be an error; it is out of sequence.

Page 236, (NH₄)₂O₂,TiO₃,H₂O₂: as printed in the source document; the final O₂ is probably an error.

Changes:

Footnotes have been moved to under the paragraph in which they are referenced; illustrations have been moved out of text paragraphs.

Some obvious minor typographical and punctuation errors have been corrected silently.

Moh’s scale has been changed to Mohs’ scale, Guèrin and Guérin to Guérin. Where there was a space between the number and the percent sign, or between the degree sign and the C, this has been deleted for the sake of consistency.

Page vii: Blomstandine changed to Blomstrandine.

Page 20, Monazite: Yttr = 1 4; changed to Yttr = 1-4;

Page 26: Osterby changed to Österby.

Page 46: Struverite changed to Strüverite as elsewhere.

Page 87: Kraus and Heitinger changed to Kraus and Reitinger.

Page 155: Footnote anchor [194] was missing in the source document, and has been inserted at the end of the paragraph.