The solution of cellulose by Schweitzer’s reagent is undoubtedly a

chemical action. Cellulose is to be regarded as a polyhydric alcohol,

with one or several atoms of hydrogen of the hydroxyl groups replaceable

by metals. According to Piest (_loc. cit._) a ‘Cupramine base’ is formed

by the replacement of this hydrogen by copper and the amino-group, NH₂.

The action of sodium hydroxide on cellulose, however, is generally

regarded rather as an additive reaction, the product, ‘alkali

cellulose,’ being usually written C₆H₁₀O₅,NaOH. A careful chemical

investigation alone can reveal the actual nature of the compound formed;

such an investigation, apart from its scientific interest, might yield

results of considerable technical importance.

~The Viscose Process.~--Shortly after the introduction of the Chardonnet

process, patents were taken out which protected a very cheap and simple

method of dissolving cellulose,[529] which had been discovered by two

well-known English authorities. Cross and Bevan. They found that

mercerisation, _i.e._ the action of the sodium hydroxide on cellulose,

produces a swollen, transparent mass, which very readily takes up carbon

disulphide. When exposed to the action of this liquid for three or four

hours, at ordinary temperatures, the mass swells further, gelatinising

and becoming soluble in water. On treatment with water, a yellowish,

extremely slimy solution is obtained, from which cellulose is

precipitated on prolonged standing, by heating, or by oxidation. The

substance is apparently a cellulose xanthate, and may be written

NaS·CS·O·C₆H₉O₄,NaOH.[530] On account of the extremely viscous nature of

the aqueous solution, Cross and Bevan gave it the name Viscoid.

[529] _Vide_, _e.g._ Cross, Bevan, and Beadle, _D. R. P._ 70999,

granted September, 1893.

[530] _Vide_ Beltzer, _Zeitsch. angew. Chem._ 1908, ~21~, 1731.

During the last few years this method of dissolving cellulose has been

employed in the manufacture of artificial silk, under the name ‘Viscose

Process.’ The product obtained is very suitable for the manufacture of

incandescent mantles, and is considerably cheaper than either the

Chardonnet or Pauly silk.

~The Acetate Process.~--Quite recently numerous experiments have been

carried out with the object of finding methods for employing the

cellulose esters of organic acids in the preparation of fabrics. The

acetate, which is generally used, gives solutions from which fibres can

be obtained which are comparable to natural silk in strength, and which

have the further advantage of being non-inflammable, and far less

readily affected by water than artificial fabrics obtained by the above

methods. It is prepared by treating cellulose with dilute acid, by which

the so-called ‘hydrocellulose’ is obtained; this is treated with a

mixture of glacial acetic acid and acetyl chloride, and the whole, after

addition of a little concentrated sulphuric acid, warmed to 65°-70°C.

As early as 1894, Cross and Bevan[531] had patented a process for this

preparation by the action of acetyl chloride in the cold on an intimate

mixture of cellulose and zinc chloride.

[531] _E._ 9676, 1894.

From the solution obtained, the acetates are precipitated by water,

washed and dried. The mixture of esters dissolves in chloroform,

nitromethane, acetic acid, phenol, pyridine, etc., and is

re-precipitated by addition of alcohol, benzene, or ligroin (petroleum

ether). On account of its non-inflammable character, cellulose acetate,

as the product is called, is being used instead of the nitrate in the

manufacture of celluloid; it is also used for non-inflammable

cinematograph films. Fibres can be obtained by forcing the solutions

through jets, and removing the solvent, as in the above processes; these

are spun into threads which are coming into increasing use, on account

of their extremely low conducting power, for the insulation of very fine

electric leads. The product is at present too expensive, however, for

use in the textile industries, or for the manufacture of mantles.

A solvent which had at one time some technical importance is zinc

chloride.[532] The concentrated aqueous solution of the salt will take

up cellulose in considerable quantity; and the solution has been used in

the preparation of carbon filaments for glow lamps.

[532] Gulbrandsen, _Prog. Age_, 1912, ~30~, 77; Wynne and Powell, _E._

16805, December, 1884.

The fabrics prepared by the processes which have been mentioned above

are of great technical value. In lustre they far surpass natural silk,

and they take dyes very well, but owing to the ease with which they

tear, they cannot be woven alone for textiles, but are always used in

‘mixed’ materials. The acetate silk, which approaches the natural fibre

in strength, is not much less expensive. Whilst the price of natural

silk is roughly 35 francs per kilo. (approx. 13_s._ 3_d._ per lb.), the

costs of production of the artificial fabrics are--Chardonnet 15 frs.,

Pauly 12 frs., Viscose 7 frs. per kilo. (respectively 5_s._ 8_d._, 4_s._

6_d._, and 2_s._ 8_d._ per lb.). Artificial silk, however, has uses

distinct from the natural fibre, and is at present a competitor with it

in one or two small fields only. Thus the production of natural silk is

ten times that of artificial silk (50,000,000 kilos. per annum to

5,000,000 kilos.) in spite of the difference in price.

Artificial silk is very susceptible to the action of water, which

weakens it very considerably. Its resistance is said to be greatly

increased by the action of formaldehyde; the fabric is plunged into a

bath containing an aqueous solution of the aldehyde, to which a little

lactic acid has been added. The chemistry of the change is discussed at

length by Beltzer (_loc. cit._).

The threads of artificial silk far surpass in lightness those spun from

vegetable fibres. A thread of twenty strands weighing one pound

avoirdupois would be more than twenty miles long. At the same time the

filaments have not the irregular tubular structure of vegetable fibres,

but are solid cylinders. The fact that the filaments are continuous, so

that there is relatively little torsion in threads spun from them, gives

artificial silk its great advantage over the natural vegetable fibres

for the manufacture of mantles. For this purpose the Pauly or

Cuprammonium silk is most suitable, though Viscose silk is almost as

good; the fibre obtained by the Chardonnet process is not quite so

useful in this direction.

~The Manufacture of Mantles from Artificial Silk.~--Whilst the fabrics

made by the various processes outlined above are more expensive than the

cotton and ramie formerly exclusively used in the mantle industry, they

have the advantage, in addition to the fact that they produce better and

more lasting mantles, that they do not need the laborious and

troublesome process of washing which is so essential in the case of the

vegetable fibres. From the nature of the methods used in its

manufacture, artificial silk can contain no mineral residue; hence the

fabric is immediately ready for impregnation.

As early as the year 1892 Schlumberger and Sinibaldi proposed the use of

Chardonnet silk for the manufacture of mantles; but their patent, a

Belgian one,[533] attracted little attention, although they stated

clearly that the denitrated silk will readily take up the lighting

fluid. Ignorance of this fact deferred the successful application of

this fibre for ten years. In 1894 De Mare suggested the preparation of

mantles by addition of the necessary salts to the collodion solution

before squirting; in the following year Knöfler used the same process,

recommending in addition the use of ammonium sulphide to denitrate the

impregnated threads. These two attempts, which were found to be

unworkable, owing to the difficulty of obtaining a homogeneous product

before squirting, were merely efforts to compete against the Auer

monopoly, resting on Welsbach’s patents, which covered impregnation of

any natural fibre. In Knöfler’s process,[534] the salts were dissolved

in alcohol and added to the collodion solution, which was then forced

through jets into water, to which ammonia was added to prevent removal

of the nitrates in solution; the threads were then denitrated with

ammonium sulphide. The ammonia treatment of course converts the nitrates

into the insoluble hydroxides, a departure which was followed in most of

the numerous patents inspired by Knöfler’s process.

[533] _Vide_ Böhm, _Zeitsch. angew. Chem._ 1912, ~25~, 657. Apparently

this patent was not taken up; no account of it has been found in the

published patents of the Belgian Government.

[534] _E._ 11038, 1895, granted July, 1895.

The first indications of the method which ultimately led to success are

to be found in a patent taken out by Plaisetty, in 1901.[535] The

specification protects the addition of thorium and cerium hydroxides to

the cuprammonium solution of cellulose, but apparently without any

inkling of the results that were to follow, and more or less

incidentally, he includes in this patent the impregnation of the

finished fabric and the subsequent treatment with ammonia. In the

following year he applied for a German patent,[536] which was granted in

May, 1903, in which he definitely protects the impregnation of the

finished fabric, and the ammonia treatment, the fabric being then washed

and dried, and burnt off as usual.

[535] _E._ 20747, 1901.

[536] _D. R. P._ 141244.

~Impregnation.~--Since the filaments from which artificial silk is

obtained are solid and rod-like in form, as opposed to the tubular

structure of cotton and ramie filaments, it is rather surprising that

the fabric should take up the lighting fluid in the necessary quantity

(_vide_ p. 295). It is found that a 50 per cent. solution of nitrates

gives the best results, the impregnation requiring half an hour; a warm

bath is usually employed. It is usual to add to the bath a quantity of

thorium hydroxide, since the thorium nitrate of commerce generally

contains nitric acid, which has a bad effect on the fabric.[537] The

excess of solution is removed by means of a glass or porcelain

centrifuge, not, as with cotton or ramie mantles, by use of a wringer;

drying must be carried out very slowly. The fabric is not cut into

lengths before impregnation, as in the case of cotton or ramie, but is

immersed in the lighting fluid in long strips.

[537] _Vide_ Buhlmann, _D. R. P._ 188427, 1907; also _E._ 6828, 1907.

~‘Fixing.’~--If the dried fabric, impregnated with the necessary salts,

be finished and burnt off in the usual way, the oxide skeleton is

extremely fragile, and soon falls to powder. The reason for this lies

probably in the explosive decomposition of the nitrates, the weight of

organic matter relative to the salts being very much less than in the

case of ramie or cotton fabrics (_vide_ p. 295). The additional ammonia

bath advocated by Knöfler (_vide supra_) was therefore adopted by

Plaisetty, and the nitrates in the dried impregnated fabric are

converted into hydroxides by this treatment. For this process, to which

the name ‘Fixing’ has been given by Böhm, numberless alternative

proposals have been made. Plaisetty’s ammonia fixing gives a mantle

which, after burning off, is exceedingly elastic and strong, but it is

nevertheless open to serious objections. Thus the nitrates may be to

some extent dissolved out by the fixing bath before precipitation of the

hydroxides has occurred; to remedy this, the impregnated fabric must be

very thoroughly dried before fixing, and in this case, apart from the

trouble involved, the acid of the commercial nitrates will attack the

fabric unless addition of thorium hydroxide has been made to the

impregnating fluid. Again, the conversion into oxides is not complete,

the outer layer first formed preventing free diffusion of the alkaline

fluid. Finally, since ammonium nitrate is formed in the reaction, a very

thorough washing is necessary to remove this salt.

It would be impossible to mention all of the numberless proposals which

have been put forward for fixing; nor are the great majority worthy of

mention.[538] One of the most important was that of Albrecht,[539] by

which hydrogen peroxide is substituted for ammonia. This reagent, as is

well known, precipitates from solutions of thorium salts ‘peroxide’

compounds (_vide_ p. 255); from the fabric impregnated with the nitrate,

free nitric acid is liberated in the reaction. Since the peroxide is

soluble in nitric acid, two baths are used, the fabric being allowed to

remain for a short time only in the first, which becomes strongly acid,

and being then transferred to the second, in which the precipitation is

completed. The burning off of the product so treated proceeds quite

quietly, and leaves a very hard and elastic skeleton. The method,

however, has the grave disadvantage that cerium salts are not

precipitated under these conditions, but escape into the solution. To

remedy this, arbitrary additions of cerium nitrate are made to the

fixing bath, but the percentage of cerium, and therefore the lighting

power (_vide_ p. 293) of mantles fixed by this method is liable to

fluctuate. A modification has been introduced[540] in which various

salts are added to the hydrogen peroxide fixing baths to prevent the

withdrawal of the cerium salt; these are chiefly acetates of the alkali

metals and allied compounds. The fabric requires washing after this

treatment.

[538] A large number of patents are mentioned by Böhm, _J. Gasbel._

1909, ~52~, 855.

[539] _D. R. P._ 188427, September, 1907; _E._ 15295, 1907.

[540] _Vide_ _E._ 2240, 1908. Cerofirm Gesellschaft, by Brit. Cerofirm

Co.

A rather similar proposal[541] substitutes for ammonia an alkaline

solution of hydrogen peroxide, obtained by dissolving sodium peroxide in

water. After saturation for a minute or so, the fabric is wrung out and

dried, there being no necessity, according to the patent, for any

subsequent washing. The same company in an earlier patent[542] suggest a

fixing bath of ‘an alkali or amine with an acid which can form insoluble

basic double salts with the earth metals,’ the said salt to be

precipitated on the fibre, whilst an alkali or amine nitrate goes into

solution; acetic and benzoic acids and phenol are mentioned. Apparently

this process did not give satisfactory results. The same may be said of

the hypochlorite method of Visseaux.[543] Equally interesting, and

doubtless equally practical is the proposal[544] to treat the dried

impregnated mantle with ozone in a closed chamber, which possibly

inspired the even more original suggestion[545] that the fabric be first

washed in ozonised water, dried, then impregnated and dried, and finally

treated with ozone. According to yet another French patent,[546] the

impregnated and dried fabric is to be treated with an alcoholic solution

of hydrofluoric acid, which will give a viscous insoluble mixture of

thorium and cerium fluorides in the fabric, and at the same time will

remove any impurities. Another patent[547] proposes the use of hydrazine

and similar bases, cerium nitrate being added to the fixing solution.

[541] _D._ 247940, June, 1912; _F._ 430417, August, 1911.

[542] _F._ 403433, September, 1909, Bruno Co.

[543] _F._ 408807, February, 1910.

[544] _F._ 414700, June, 1910.

[545] _F._ 422643, January, 1911.

[546] _F._ 426156, April, 1911.

[547] _E._ 11904, 1909.

Innumerable suggestions have been made for fixing by means of ammonia

gas, or vapours of organic bases.[548] An English patent granted in

February 1910[549] protects ‘various improvements,’ which consist in

carrying out a preliminary treatment with steam, impregnation with the

solution of nitrates, conversion of nitrates into oxides either by steam

carrying ammonia, pyridine, etc., or by the action of these vapours

without steam in a vacuum, all in one chamber, which can be exhausted or

filled with various solutions or vapours as required.

[548] _Vide_, _e.g._ _D. R. P._ 199615 of June, 1908.

[549] _E._ 25549, 1908.

More recently, the use of organic salts of thorium and cerium for

impregnation has been proposed by Dr. F. W. Wirth;[550] in fixing the

impregnated fabric with hydrogen peroxide, the cerium is not removed in

solution, since the weak organic acid formed will not dissolve cerium

peroxide. The same author has also suggested[551] the addition to the

fixing bath of substances which absorb oxygen from the air--_e.g._

sodium hydrogen sulphite, resorcinol, tannin--to prevent removal of

cerium. He has also advocated impregnation with amorphous salts,[552]

which will obviate the necessity for any subsequent fixing treatment,

the hypophosphites and double compounds with ammonium oxalate being

specified. Attempts have been made to achieve the same end by other

methods. Thus Silbermann[553] has proposed a preliminary treatment with

alkalies (mercerisation); the fabric is treated with concentrated sodium

hydroxide solution in absence of air for half an hour, pressed through

rollers, and plunged into the impregnating solution. Two years

previously a patent was taken out by Drossbach[554] to protect the use

of colloidal solutions of the hydroxides. To a boiling suspension of

well-washed, freshly-precipitated thorium hydroxide, a solution of a

small quantity of the nitrate is gradually added; after half an hour a

colloidal solution is obtained, which, after the addition of the

required quantity of cerium nitrate, and dilution to a suitable extent,

is employed directly for impregnation. The patent states that this

solution is more readily absorbed than the ordinary nitrate solution,

but the statement has been questioned.

[550] _Chem. Zeitg._ 1911, ~35~, 752.

[551] _Zeitsch. angew. Chem._ 1912, ~25~, 922.

[552] _Chem. Zeitg._ 1911, ~35~, 752.

[553] _Chem. Zeitg._ 1911, ~35~, 1037.

[554] _D. R. P._ 212842, August, 1909; _vide_ also Kreidl and Heller,

_E._ 17862, 1909, and _D. R. P._ 228203, 1910.

Artificial silk itself is of a colloidal nature, the solidification of

the filaments of cellulose during the manufacture being rather in the

nature of a coagulation than of a precipitation; it is to this fact that

the fibres owe their solid, rod-like structure, and it is probably this

circumstance also which determines the very intimate absorption of the

hydroxides or peroxides produced by fixing. It is well known that

colloidal substances under some circumstances possess the property of

clinging tenaciously to foreign bodies, exhibiting the so-called

phenomenon of adsorption. The strength and elasticity of the oxide

skeleton, obtained when the fixed and dried fabric is subjected to the

operation of burning off, are presumably to be referred to such a

relation between the cellulose of the fibres and the insoluble thorium

and cerium compounds, precipitated by one of the methods of fixing

described.

~The Final Stages.~--The treatment of the fabric after impregnation and

fixing differs only slightly from that used for the impregnated ramie

and cotton products. The dried strips are cut into suitable lengths, and

the head is drawn together with asbestos and threaded across. No tulle

or gauze is required, the end being simply turned down before threading.

After the ordinary strengthening process for the head (_vide_ p. 296)

the process of manufacture was, until recently, finished, the goods

being sent out in the unburnt condition, on account of the difficulties

of collodinisation. These have now been overcome, so that the mantles

are burnt off and collodinised as usual. Burning off and shaping are now

frequently effected in one operation by machine; the nature of the

methods by which the fibre is made produces a uniform fabric, and if the

earlier processes are carefully carried out, a uniform product is

obtained, which is therefore suitable for machine treatment.

CHAPTER XXI

OTHER TECHNOLOGICAL USES OF THE CERIUM AND YTTRIUM ELEMENTS, ZIRCONIUM

AND THORIUM

The technical uses of the members of this group of the elements we are

considering, apart from the employment in the manufacture of

incandescent mantles, are at present very restricted. Innumerable

proposals for the employment of the compounds of cerium and the allied

metals, which are obtained in such large quantities as by-products in

the thorium industry, have been put forward, but the actual extent to

which they are utilised is so small that only an insignificant fraction

of the available quantities is annually required. In the metallic form,

a limited application is found for various alloys, _e.g._ the so-called

pyrophoric alloys, misch metal, and the magnesium and aluminium alloys.

Various compounds of the elements, as well as some alloys, have been

suggested for use in arc-lamp electrodes, and the use of the metals

themselves, as well as of various salts, for the manufacture of

flashlight powders, is protected by several patents. Investigations have

been made to determine the value of the oxides and sulphates as

catalysts in the contact process for the manufacture of sulphuric acid,

and one patent states that the yield obtained is equal to that given by

platinised asbestos. Cerium salts have been proposed for tanning, and in

the preparation of enamels; cerium sodium sulphate is used in the

catalytic oxidation of aniline to aniline black. The oxalate has a very

slight use in medicine. The oxidising power of ceric salts is of some

use in photography; ceric sulphate in acid solution is also said to be

an efficient oxidising agent for aromatic hydrocarbons. On account of

the deep colour of the higher oxide of praseodymium, didymium salts

find a limited application for marking textiles.

Compounds of the yttrium group have at present no technical importance.

They were formerly used to some extent for the manufacture of filaments

for Nernst lamps, but with the introduction of metal filament lamps in

electric lighting, the demand for Nernst lamps and consequently for the

yttria oxides, has to a very great extent died away.

Zirconium and its compounds, on the other hand, promise to become of

some technical importance. The metal received considerable attention in

the earlier stages of experimental work on metallic filaments for

electric lighting, but it has been shown that its melting-point is not

sufficiently high to allow of extended use in this direction. The

carbide has been proposed for the same purpose, but is even less

suitable; this compound, however, on account of its great hardness, is

likely to find employment as an abrasive, and in glass-cutting. The

oxide, which occurs in nature in an impure form as the mineral

Baddeleyite (_q.v._), is employed in the manufacture of ‘Siloxide’ glass

and of enamels, as a pigment and polishing agent, and in various forms

of lamps, _e.g._ the Nernst and Bleriot lamps, the Drummond light, etc.

Far more important, however, is its use for fire-resistant crucibles,

furnace linings and supports, etc., for which its refractory nature

renders it particularly suitable. On account of its high specific

gravity and non-poisonous character, it has been proposed for use in the

Röntgen ray examination of the human body. Quite recently, metallic

zirconium has been employed in metallurgy; addition of small quantities,

in the form of suitable alloys, is said to secure sound castings, with

increased strength and resistance to acids.

THE CERIUM GROUP

~Pyrophoric Alloys.~--It has long been known that the metals of the

cerium group possess the property, when scratched or struck, of throwing

off glowing particles; this power of emitting sparks is not lost when

the metals are alloyed, so long as the percentage of foreign metal is

not allowed to become too high. In a patent[555] protecting the use of

various ‘pyrophoric alloys,’ as these spark-giving alloys are called,

Auer states that the pure metals do not show this property, which only

appears when foreign metals are present; he accordingly patents alloys

of the cerium metals with iron, specifying particularly the alloy with

30 per cent. of the latter element. Auer’s statement has been

contradicted,[556] and it seems to be generally accepted that

misch-metal[557] of ordinary technical purity has the property of

sparking when scratched. This alloy of the cerium metals, however, is

far too soft to be useful for the purpose, and the addition of some

foreign element is required to obtain the strength, hardness, and

brittleness necessary in the various forms of ‘lighters.’ Besides the

addition of iron, the use of tin, lead, zinc, cadmium, silicon, etc.,

has been patented.[558]

[555] _E._ 16853, 1903; _D. R. P._ 154807.

[556] _Vide_ Böhm, _Chem. Zeitg._ 1910, ~34~, 361.

[557] The crude mixture of cerium, lanthanum, neodymium, praseodymium,

samarium, etc., with small quantities of iron and other metals,

obtained by reduction of the earth-compounds formed as by-products in

the thorium industry, is technically known as ‘misch-metal.’

[558] _F._ 439058, March, 1912.

Various forms of these lighting devices are manufactured;[559] in all of

these the sparks produced by scratching the pyrophoric alloy with

hardened steel, by means of some simple mechanical device, is caused to

ignite a fragment of tinder, or a wick supplied with a suitable liquid,

_e.g._ methyl alcohol, benzene, or petrol. In the numberless forms of

cigarette-lighters at present before a somewhat indifferent public, the

friction is obtained by means of a toothed wheel, actuated by a spring

which is released when the device is opened. Many forms of gas lighter

are also on the market, but the demand for them is very small. Many

attempts have been made to adapt the device to the ignition of the Davy

miners’ lamp, but none have been successful, since it is impossible to

prevent the sparks flying through the gauze. Much work has also been

spent in efforts to utilise the pyrophoric alloys for the automatic

ignition of incandescent gas-lamps, but these have been equally

unsuccessful, so that it may be said that important technical

applications of this interesting property have still to be made.

[559] _Vide_ Böhm, _Chem. Zeitg._ 1910, ~34~, 377; also Kellermann,

_Die Ceritmetalle und ihre pyrophoren Legierungen_, Wilhelm Knapp,

Halle, 1912, pp. 94 _et seq._

Auer prepared his alloys by addition of iron, or other heavy metal, to

the fused mixture of cerium metals obtained in the electrolytic

apparatus employed for the production of the latter. They can, however,

be prepared by fusing together the required quantities of foreign metal

and misch-metal, the latter being obtained by processes other than those

of electrolysis usually employed. The rare metals were obtained by the

earlier chemists in a very impure state by reduction of the halogen or

double halogen compounds with sodium or potassium. More recently[560]

much purer products have been obtained--especially in the case of

zirconium--by the action of metallic calcium, in the form of powder, on

the oxides. Another method,[561] which has been employed in the

preparation of metallic filaments for lamps, consists in heating the

oxides with powdered magnesium in an atmosphere of hydrogen or nitrogen;

by this means, hydrides or nitrides are obtained, which on heating

decompose into the gas and the metal.

[560] _Vide_ Kuzel and Wedekind, _E._ 23215, 1909.

[561] _Electrodon Gesellschaft_, _D. R. P._ 154691, September, 1904.

The ease with which misch-metal and its alloys with iron and other

elements throw off glowing particles when struck is due to the low

ignition temperature of cerium, and the energy with which it combines

with oxygen. When such alloys are scratched, small fragments are struck

off, which are raised to the ignition temperature by the heat of

friction. It is generally accepted, however, that this explanation is by

no means a complete one, and the existence of a pyrophoric suboxide was

suggested.[562] The theory was advanced that the pyrophoric properties

of the alloys were due primarily to the formation on the surface of a

film of this sub-oxide, and the partial oxidation of cerium alloys,

protected by patent (_loc. cit._), was said to cause a marked increase

in the ease with which sparks could be obtained. In this connection, an

experiment of Hirsch, who has thoroughly investigated the properties of

metallic cerium,[563] is of interest. He found that when the element is

warmed in a sealed glass bottle, a black powder forms on the surface,

which, when the bottle is opened, ignites spontaneously. It is probable

that this black sub-oxide plays an important part in the production of

sparks from the ordinary pyrophoric alloys.

[562] _Vide_ _F._ 407117, December, 1909.

[563] _Met. Chem. Eng._ 1911, ~9~, 543.

~Other Alloys.~--On account of the great affinity of the cerium metals

for oxygen, misch-metal has been suggested as a reducing agent,[564] as

have also the alloys of cerium and magnesium;[565] the formation of the

latter is endothermic, so that they act much more vigorously than either

metal separately. The alloys of cerium with tin and aluminium have been

thoroughly investigated from the stand-point of metallography, by

Vogel.[566] It has recently been claimed that the addition of very small

quantities of cerium to aluminium has a very marked effect, the rare

earth metal acting as a purifying agent,[567] and greatly improving the

properties of the aluminium. The cerium may be introduced as fluoride,

either to the electrolytic bath in which the aluminium is being

prepared, or to the latter metal, after preparation, in the fused state.

The most favourable effect is said to be produced by 0·2 per cent. of

cerium.

[564] _Vide_, _e.g._ Escales, _D. R. P._ 145820, October, 1903.

[565] Hirsch, _loc. cit._

[566] _Zeitsch. anorg. Chem._ 1911, ~72~, 319; 1912, ~75~, 41.

[567] Borchers and Barth, _D. R. P._ 246484, May, 1912.

~Applications of the Cerium Compounds.~[568]--One of the earliest

investigations in which cerium compounds were examined with a view to

technical employment, was that of Kruis,[569] who made experiments on

the comparative value of the salts of different metals as catalysts in

the manufacture of aniline black. He showed that a solution of aniline

with an oxidising agent (potassium chlorate or chromate) develops no

colouration unless a salt of a heavy metal is present. In the case of

the fabric impregnated with the solution, the only metals of which

compounds were found suitable for producing a colour were copper, which

was then generally used for the purpose, and cerium, iron, and

manganese. Of these, cerium, used in the form of the double sulphate,

was found to be by far the most suitable, and moreover to have the

advantage that only small quantities are required; the price was at that

time too high to allow of its use, but it has since been employed.[570]

Cerium compounds have also been proposed as mordants for alizarin,[571]

but they do not appear ever to have come into general use.

[568] An account of the various suggestions for the technical

employment of the rare earth elements, by Dr. Max Speter, will be

found in Dammer, _Die Chemische Technologie der Neuzeit_, Stuttgart,

1910, vol. i. pp. 500-504.

[569] _Dingl. Polyt. J._ 1874, ~212~, 347.

[570] _Vide_ Buhrig, _Dingl. Polyt. J._ 1879, ~231~, 77; and _Abstr.

Chem. Soc._ 1879, ~36~, 683.

[571] _Vide_ Witt, _Chem. Ind._ 1896, ~19~, 156.

In photography, ceric sulphate has been employed for some time for the

purpose of ‘reducing,’ _i.e._ removing silver from over-developed

negatives.[572] It is said to act very evenly and rapidly, the small

quantity of free sulphuric acid required to hold the salt in solution

having no bad effect. More recently, cerium salts have been proposed for

use in colour photography.[573] An emulsion is obtained by adding salts

of iron, uranium, or cerium to a colloidal solution of albumen in

ammonia, borax solution, or sodium carbonate solution; this is spread on

the paper or negative, and is said to be readily sensitive to light.

[572] _Vide_ Lumière, _Bull. Soc. franc. Photog._ (2) 1900, ~16~, 103.

Also _E._ 470, 1900.

[573] Fateau, _E._ 20740, 1907.

The crude mixture of cerous sulphate with basic sulphates of other

elements of the cerium group, which has been patented for use as a

catalyst in the contact process for the manufacture of sulphuric

acid,[574] is prepared from the earth compounds obtained as by-products

in the treatment of monazite. These are converted into the sulphates,

and, after evaporation of the excess of sulphuric acid, heated for

several hours at a low red heat (300°-600°C.). The porous mass is then

broken, and is ready for use. It is stated that a nearly quantitative

yield of sulphur trioxide is obtained, and that the mixture acts more

efficiently than pure cerous sulphate. The reaction is said to depend on

the continuous formation and decomposition of the ceric salt, thus:

Ce₂(SO₄)₃ + SO₂ + O₂ = 2Ce(SO₄)₂

2Ce(SO₄)₂ = Ce₂(SO₄)₃ + SO₃ + O

[574] Hölbling, _D. R. P._ 142144 and _F._ 326321 of May, 1903.

This process does not appear to have come into general use.

A general patent had been taken out in 1901, protecting the use of

oxides of the rare earth elements for ‘high-temperature catalysis’ in

the manufacture of sulphuric acid,[575] but the oxides do not seem to be

very efficient.[576]

[575] Meister, Lucius and Brüning, _E._ 1385, 1901.

[576] _Vide_ Plüddemann, Dissertation, _Beitrag zur Aufklärung des

Schwefelsäurekontaktprozesses_, Berlin, 1907.

It has also been proposed to utilise the oxidising power of ceric salts

in acid solution[577] for the preparation of aldehydes, quinones, etc.,

from aromatic hydrocarbons, for which purpose they are claimed to be

more efficient than chromates. By the use of a crude cerium dioxide

(60-70 per cent. CeO₂) obtained by the ignition of the by-products of

the thorium industry, good yields were obtained of benzaldehyde,

naphthaquinone and anthraquinone from toluene, naphthalene and

anthracene respectively.

[577] Meister, Lucius and Brüning, _D. R. P._ 158609, March, 1905.

Garelli[578] has examined the action of cerium salts in tanning; he

states that with neutral solutions, effects very similar to those

produced by aluminium salts are obtained, but Eitner, who has also

examined the question,[579] is of opinion that the cost of isolating and

purifying the salts from the monazite residues renders their employment

for this purpose impossible.

[578] _J. Soc. Chem. Ind._ 1912, ~31~, 830.

[579] _Ibid._ 1911, ~30~, 1128.

The fluoride, silicofluoride, and dioxide have also been proposed for

the preparation of enamels,[580] but do not give satisfactory results.

[580] Rickmann and Rappe, _D. R. P._ 99165, September, 1898; also _D.

R. P._ 203773, October, 1908.

Several patents protect the use of rare earth compounds for flashlight

powders. For most of the mixtures covered, it is claimed that the usual

defects of fumes, slow firing, etc., are absent. The usual recipes[581]

are for magnesium or aluminium powder with chromates, nitrates, or

similar salts of thorium, cerium, etc.; in one case[582] the rare earth

metals, alloyed with barium, silicon, uranium, or titanium, are to be

used with ‘an oxidising agent which leaves a non-volatile residue.’ None

of these mixtures appears to have been successful.

[581] _Vide_, _e.g._ _E._ 14692, 1908; _D. R. P._ 158215.

[582] _F._ 403722, October, 1909.

Cerium compounds have also been proposed for use in arc-lamp electrodes;

it is claimed that they give a very intense light, one patent[583]

adding that the presence of cerium peroxide and a little fluorspar

causes the arc to burn evenly and quietly. In another, the use of a

mixture of tungstates or molybdates of the alkaline earths, with

fluorides of the rare earth elements is protected;[584] the use of

pyrophoric alloys, either entirely, or for the core of the electrode,

has also been suggested.[585]

[583] _E._ 414707, June, 1910.

[584] _F._ 431040, August, 1911; also _E._ 21374, 1909.

[585] _E._ 8150, 1909.

~The Nernst Lamp.~--The first efforts which were made for the employment

of electricity in illumination endeavoured to utilize the heat produced,

when a current traverses a very thin metallic filament, to raise the

conductor to incandescence. Numerous efforts were made to adapt platinum

to this purpose, but its melting-point was finally admitted to be too

low; at length it was found possible to produce carbon filaments, and

the well-known carbon lamps came into use. Numerous attempts were made

to effect improvements;[586] one plan was to coat the carbon filament,

after its production, with a skin of metallic conductor, and zirconium

and thorium were among the metals proposed in this connection.[587] The

first really important advance, however, was effected by Nernst, who

took up the study of ‘conductors of the second order,’ and within a few

months succeeded in adapting these to the purposes of illumination

(1897-1898). The Nernst lamps gave a very intense white light with

considerably less consumption of electricity than the carbon filament

lamps; they enjoyed a very considerable vogue for some years, but have

been almost entirely displaced by the cheaper metal filament lamps,

which were occupying the attention of Auer von Welsbach at the time

Nernst perfected his invention.[588]

[586] The reader is recommended to consult the _Jahresberichte über

die Leistungen der Chemischen Technologie_ of Fischer, Section

‘Beleuchtung,’ for the years 1898-1901 inclusive, from which some idea

may be obtained of the innumerable proposals and suggestions, usually

protected by patent, which were put forward at this time.

[587] _Vide_, _e.g._ _D. R. P._ 153959.

[588] _Vide_ _E._ 1535, 13116 and 17580, 1898.

In his first patent,[589] Nernst proposed the use of a rod of magnesia

or zirconia as filament; these oxides, which belong to his class of

conductors of the second order, are non-conductors at ordinary

temperatures, but their resistance decreases as the temperature rises,

so that at high temperatures they will conduct electricity at the

ordinary voltage. The preliminary heating was at first effected by means

of a Bunsen burner, but a later patent[590] of the same year protects a

method of heating by means of a platinum spiral in an auxiliary circuit,

which is automatically cut out when the current in the main circuit,

bearing the filament, attains its required strength. In the following

year[591] it was found that filaments composed of mixtures of oxides

were far more suitable than the earlier magnesia or zirconia rods;

yttria, thoria, and zirconia were the chief oxides used, small

quantities of ceria being occasionally introduced. With these filaments,

the increase of conductivity with temperature is far more rapid than

with the pure oxides; the preliminary heating required, therefore, is

less and the light obtained more intense. The filaments used were in the

form of rods or spirals obtained by compressing the powdered oxides.

[589] _E._ 19424, 1897.

[590] _E._ 23470, 1897.

[591] _E._ 6135, 1898.

The Nernst filaments differ markedly from those of the ordinary electric

glow lamp in that they are not conductors in the ordinary sense (or of

the first order, as Nernst puts it) but electrolytes, the passage of the

current being actually attended by an electro-chemical change in the

filament.[592] The oxide is ionised; the ions of the metals travel to

the cathode or negative pole, where the liberated atoms of metal

instantly recombine with the oxygen of the air, whilst oxygen ions

travel to the anode, from which the gas is liberated. There is thus a

gradual redistribution, resulting in accumulation of oxide at the

cathode with a corresponding loss at the anode, which is balanced, after

some time, by diffusion, so that equilibrium is attained. In consequence

of this redistribution the filament glows more brightly at the anode,

where it is thinnest, than at the cathode.

[592] _Vide_ Nernst, _Zeitsch. Elektrochem._ 1899, ~6~, 41.

INDUSTRIAL APPLICATIONS OF ZIRCONIUM

It has already been mentioned that zirconium received considerable

attention as a suitable substance for the preparation of metallic

filaments during the early stages of their development. Whilst at the

present time this element has been abandoned for the purpose,[593]

several zirconium lamps were at one time on the market, and a brief

mention of some of the work done in this direction may not be out of

place.

[593] _Vide_ Baumhauer, _Zeitsch. angew. Chem._ 1910, ~23~, 2065.

One of the general methods for the preparation of the metallic filaments

may be illustrated by a patent taken out in 1902 by Sander,[594] for the

preparation of filaments of zirconium, with or without addition of

zirconium carbide. The metal, or a compound which on heating will yield

the metal and a volatile substance which can be removed, is prepared in

a finely divided condition, and made into a paste with some organic

binding material; the paste is then forced through a tiny aperture, and

the resulting thread is shaped and heated to a high temperature _in

vacuo_ or in an inert atmosphere. If an organic substance be used to

form a paste with metallic zirconium, the final process of heating

results in the formation of the carbide; the same compound is also

obtained by another process protected by Sander (_loc. cit._) in which

the hydride of zirconium, prepared by the reduction of the oxide by

means of powdered magnesium in an atmosphere of hydrogen, is mixed with

a cellulose solution, and the liquid treated as in the manufacture of

artificial silk, the threads obtained being then heated to remove all

organic matter as far as possible.

[594] _D. R. P._ 133701, July, 1902.

The carbide is also probably obtained by the process of the British

Thomson-Houston Company, in which advantage is taken of the fact that

zirconium oxalate is a pasty gelatinous substance, which can be forced

through a die to form a thread without addition of any agglutinating

agent. The oxalate, precipitated by addition of ammonium oxalate to a

solution of a zirconium salt, is mixed with finely divided carbon, and

the threads obtained from the pasty mass heated to a very high

temperature in a furnace.[595] Zirconium oxalate is also proposed as a

binding material for powdered tungsten, in the preparation of filaments

from that metal.[596]

[595] _E._ 5415, 1908.

[596] _E._ 10590, 1908.

The compounds of zirconium and thorium with elements of group VB,

according to two German patents,[597] are suitable for the preparation

of metallic filaments in much the same way. Thorium, titanium, and

zirconium are also among the metals which, it is claimed, can be

obtained in the pure fused state by heating in an electric arc _in

vacuo_, so that filaments can be drawn directly.[598]

[597] _D. R. P._ 153958 and 154299, September, 1904.

[598] _Ibid._ 169928, April, 1906.

Metallic zirconium and its alloys have recently been employed in

metallurgy. The pure metal can be obtained by the calcium reduction of

Kuzel and Wedekind (_vide_ p. 316); zirconia is not reduced by powdered

aluminium (Goldschmidt’s process), but alloys of zirconium and iron can

be easily obtained by the reduction of mixtures of the two oxides by

this method. Alloys can be obtained containing up to 35 per cent. of

zirconium; this ferro-zircon, as it is called, has been used to some

extent recently in place of ferro-titanium (_vide infra_) for the

purification of steels.[599] Addition of small quantities of zirconium

to steels, brass, copper, etc., is said to secure sound castings, and to

increase considerably the strength and resistance to acids of the metal.

[599] _Vide_ Weiss, _E._ 29376, 1910, and Lesmüller, _D. R. P._

231002, February, 1911.

~The Technical Uses of Zirconia.~--Since the discovery of Baddeleyite,

the natural oxide of zirconium (_vide_ p. 75), which occurs in large

quantities in Brazil, many proposals have been brought forward for the

employment of this compound. Its application to the manufacture of

glasses and enamels will be referred to in the next chapter. Patents

have been taken out protecting its use for the preparation of white

pigments,[600] as a toilet-powder,[601] and as a polishing powder,[602]

for it is extremely stable towards chemical reagents, very voluminous,

and at the same time very hard. It has long been employed for coating

the lime and magnesia pencils used in the Drummond or ‘lime’ light; and

recently it has been employed for the headlights of automobiles, in the

Blériot lamp,[603] in which a rod of zirconia is heated in a blowpipe

flame fed with oil vapour and oxygen.

[600] _D. R. P._ 235495.

[601] _Ibid._ 237624.

[602] _Ibid._ 230757.

[603] _Ibid._ 174313, September, 1906.

By far the most important property of the oxide, from the technical

point of view, is the ease with which it resists high temperatures. The

natural oxide can be freed, to a very large extent, from the iron oxide

which it encloses, by the prolonged action of hydrochloric acid;

experiments were carried out on the material so obtained by

Simonis,[604] who showed that by prolonged heating at a high

temperature, the remaining impurities, chiefly ferric oxide and silica,

could be volatilised, leaving the zirconia unchanged. Riecke[605] showed

that whilst the oxide is very suitable for the manufacture of highly

resistant crucibles, its use is restricted by the fact that it is easily

reduced by carbon at high temperatures, forming the carbide.

[604] _Sprechsaal_, 1908, ~41~ (1), 210.

[605] _Ibid._ 214.

Weiss and Lehmann have carried out exhaustive experiments on the

preparation of crucibles of zirconia.[606] They worked first with

mixtures of zirconia and magnesia, with phosphoric acid as a binding

material; the best results were obtained with a mixture of 90 per cent.

zirconia and 10 per cent. magnesia, which gave extraordinarily resistant

crucibles. Prolonged heating at temperatures over 1900°C. eliminated

all the phosphoric acid by volatilisation; the crucibles could then be

heated in the blowpipe flame and plunged immediately into cold water

without cracking or breaking, and were not affected by fused sodium

hydroxide or potassium hydrogen sulphate. Crucibles were also made with

the addition of potassium and sodium salts, and were found to answer

very well; platinum could be melted in them to a mobile liquid. Similar

crucibles are already on the market.

[606] _Zeitsch. anorg. Chem._ 1910, ~65~, 218.

As early as 1904 the use of zirconia was suggested for coating

muffles, retorts, and tubes which are required to withstand high

temperatures.[607] In 1906 it was proposed[608] for the manufacture of

crucibles in which rock-crystal (quartz) is fused for the preparation of

quartz-glass, since zirconia is not attacked by molten silica. It

promises to be of the greatest use in all cases where a very refractory

material, stable towards the ordinary chemical reagents, is required.

[607] Pufahl, _D. R. P._ 156756.

[608] Heræus Co., _D. R. P._ 179570.

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.