[1] The importance of the commerce between Ireland and Gaul in early
times, and in particular the trade in wine, has been insisted upon by
H. Zimmer in papers in the _Abh. d. Berl. Akad. d. Wissenschaften_
(1909).
[2] On the subject of Ptolemy's description of Ireland see articles
by G. H. Orpen in the _Journal of the Royal Society of Antiquaries of
Ireland_ (June 1894), and John MacNeill in the _New Ireland Review_
(September 1906).
[3] Scholars are only beginning to realize how close was the
connexion between Ireland and Wales from early times. Pedersen has
recently pointed out the large number of Brythonic and Welsh loan
words received into Irish from the time of the Roman occupation of
Britain to the beginning of the literary period. Welsh writers now
assume an Irish origin for much of the contents of the Mabinogion.
[4] It seems probable that the celebrated monastery of Whithorn in
Galloway played some part in the reform movement, at any rate in the
north of Ireland. Findian of Moville spent some years there.
[5] The O'Neills who played such an important part in later Irish
history do not take their name from Niall Noigiallach, though they
are descended from him. They take their name from Niall Glundub (d.
919).
[6] At this period it is extremely difficult to distinguish between
Norwegians and Danes on account of the close connexion between the
ruling families of both countries.
[7] This name survives in Fingall, the name of a district north of
Dublin city. Dubgall is contained in the proper names MacDougall,
MacDowell.
[8] In Anglo-Norman times the Scandinavians of Dublin and other
cities are always called Ostmen, i.e. Eastmen; hence the name
Ostmanstown, now Oxmanstown, a part of the city of Dublin.
[9] On the name see K. Meyer _Erin_, iv. pp. 71-73.
[10] Donaban, the son of this Ivar of Waterford, is the ancestor of
the O'Donavans, Donoban that of the O'Donovans.
[11] The term _rath_ was perhaps applied to the rampart, but both
_lis_ and _rath_ are used to denote the whole structure.
[12] See D'Arbois de Jubainville, _Revue celtique_, xxv. 1 ff., 181
ff.
[13] The whole question is discussed by Mr J. H. Round in his article
on "The Pope and the Conquest of Ireland" (_Commune of London_, 1899,
pp. 171-200), where further references will be found.
IRELAND, CHURCH OF. The ancient Church of Ireland (described in the
Irish Church Act 1869 by this its historic title) has a long and
chequered history, which it will be interesting to trace in outline. The
beginnings of Christianity in Ireland are difficult to trace, but there
is no doubt that the first Christian missionary whose labours were
crowned with any considerable success was Patrick (fl. c. 450), who has
always been reckoned the patron saint of the country. For six centuries
the Church of which he was the founder occupied a remarkable position in
Western Christendom. Ireland, in virtue at once of its geographical
situation and of the spirit of its people, was less affected than other
countries by the movements of European thought; and thus its
development, social and religious, was largely independent of foreign
influences, whether Roman or English. In full communion with the Latin
Church, the Irish long preserved many peculiarities, such as their
monastic system and the date at which Easter was kept, which
distinguished them in discipline, though not conspicuously in doctrine,
from the Christians of countries more immediately under papal control
(see IRELAND: _Early History_). The incessant incursions of the Danes,
who were the scourge of the land for a period of nearly three hundred
years, prevented the Church from redeeming the promise of her infancy;
and at the date of the English conquest of Ireland (1172) she had lost
much of her ancient zeal and of her independence. By this time she had
come more into line with the rest of Europe, and the Synod of Cashel put
the seal to a new policy by its acknowledgment of the papal jurisdiction
and by its decrees assimilating the Church, in ritual and usages, to
that of England. There was no thought of a breach of continuity, but the
distinctive features of Celtic Christianity gradually disappeared from
this time onwards. English influence was strong only in the region round
Dublin (known as the Pale); and beyond this district the Irish were not
disposed to view with favour any ecclesiastical reforms which had their
origin in the sister country. Thus from the days of Henry VIII. the
Reformation movement was hindered in Ireland by national prejudice, and
it never succeeded in gaining the allegiance of the Irish people as a
whole. The policy which directed its progress was blundering and stupid,
and reflects little credit on the English statesmen who were responsible
for it. No attempt was made to commend the principles of the Reformation
to the native Irish by conciliating national sentiment; and the policy
which forbade the translation of the Prayer Book into the Irish
language, and suggested that where English was not understood Latin
might be used as an alternative, was doomed to failure from the
beginning. And, in fact, the reformed church of Ireland is to this day
the church of a small section only of the population.
The Reformation period begins with the passing of the Irish Supremacy
Act 1537. As in England, the changes in religion of successive
sovereigns alternately checked and promoted the progress of the
movement, although in Ireland the mass of the people were less deeply
affected by the religious controversies of the times than in Great
Britain. At Mary's accession five bishops either abandoned, or were
deprived of, their sees; but the Anglo-Irish who remained faithful to
the Reformation were not subjected to persecution such as would have
been their fate on the other side of the Channel. Again, under
Elizabeth, while two bishops (William Walsh of Meath and Thomas Leverous
of Kildare) were deprived for open resistance to the new order of
things, and while stern measures were taken to suppress treasonable
plotting against the constitution, the uniform policy of the government
in ecclesiastical matters was one of toleration. James I. caused the
Supremacy Act to be rigorously enforced, but on political rather than on
religious grounds. In distant parts of Ireland, indeed, the unreformed
order of service was often used without interference from the secular
authority, although the bishops had openly accepted the Act of
Uniformity.
The episcopal succession, then, was unbroken at the Reformation. The
Marian prelates are admitted on all hands to have been the true bishops
of the Church, and in every case they were followed by a line of lawful
successors, leading down to the present occupants of the several sees.
The rival lines of Roman Catholic titulars are not in direct succession
to the Marian bishops, and cannot be regarded as continuous with the
medieval Church. The question of the continuity of the pre-Reformation
Church with the Church of the Celtic period before the Anglo-Norman
conquest of Ireland is more difficult. Ten out of eleven archbishops of
Armagh who held office between 1272 and 1439 were consecrated outside
Ireland, and there is no evidence forthcoming that any one of them
derived his apostolic succession through bishops of the Irish Church. It
may be stated with confidence that the present Church of Ireland is the
direct and legitimate successor of the Church of the 14th and 15th
centuries, but it cannot so clearly be demonstrated that any existing
organization is continuous with the Church of St Patrick. In the reign
of James I. the first Convocation of the clergy was summoned in Ireland,
of which assembly the most notable act was the adoption of the "Irish
Articles" (1615). These had been drawn up by Usher, and were more
decidedly Calvinistic in tone than the Thirty-nine Articles, which were
not adopted as standards in Ireland until 1634, when Strafford forced
them on Convocation. During the Commonwealth period the bishoprics which
became vacant were not filled; but on the accession of Charles II. the
Church was strengthened by the translation of John Bramhall (the most
learned and zealous of the prelates) from Derry to the primatial see of
Armagh, and the consecration of twelve other bishops, among whom was
Jeremy Taylor. The short period during which the policy of James II.
prevailed in Ireland was one of disaster to the Church; but under
William and Mary she regained her former position. She had now been
reformed for more than 100 years, but had made little progress; and the
tyrannical provisions of the Penal Code introduced by the English
government made her more unpopular than ever. The clergy, finding their
ministrations unacceptable to the great mass of the population, were
tempted to indolence and non-residence; and although bright exceptions
could be named, there was much that called for reform. To William King
(1650-1729), bishop of Derry, and subsequently archbishop of Dublin, it
was mainly due that the work of the Church was reorganized, and the
impulse which he gave it was felt all through the 18th century. His
ecclesiastical influence was exerted in direct opposition to Primate
Hugh Boulter and his school, who aimed at making the Established Church
the instrument for the promotion of English political opinions rather
than the spiritual home of the Irish people. In 1800 the Act of Union
was passed by the Legislature; and thenceforward, until
Disestablishment, there was but one "United Church of England and
Ireland."
Continuous agitation for the removal of Roman Catholic disabilities
brought about in 1833 the passing of the Church Temporalities Act, one
of the most important provisions of which was the reduction of the
number of Irish archbishoprics from four to two, and of bishoprics from
eighteen to ten, the funds thus released being administered by
commissioners. In 1838 the Tithe Rentcharge Act, which transferred the
payment of tithes from the occupiers to the owners of land, was passed,
and thus a substantial grievance was removed. It became increasingly
plain, however, as years passed, that all such measures of relief were
inadequate to allay the dissatisfaction felt by the majority of Irishmen
because of the continued existence of the Established Church. Her
position had been pledged to her by the Act of Union, and she was
undoubtedly the historical representative of the ancient Church of the
land; but such arguments proved unavailing in view of the visible fact
that she had not gained the affections of the people. The census of 1861
showed that out of a total population of 5,798,967 only 693,357 belonged
to the Established Church, 4,505,265 being Roman Catholics; and once
this had been made clear, the passing of the Act of Disestablishment was
only a question of time. Introduced by Mr Gladstone, and passed in 1869,
it became law on the 1st of January 1871.
The Church was thus suddenly thrown on her own resources, and called on
to reorganize her ecclesiastical system, as well as to make provision
for the maintenance of her future clergy. A convention of the bishops,
clergy, and laity was summoned in 1870, and its first act was to declare
the adherence of the Church of Ireland to the ancient standards, and her
determination to uphold the doctrine and discipline of the Catholic and
Apostolic Church, while reaffirming her witness, as Protestant and
Reformed, against the innovations of Rome. Under the constitution then
agreed on, the supreme governing body of the Church is the General
Synod, consisting of the bishops and of 208 clerical and 416 lay
representatives of the several dioceses, whose local affairs are managed
by subordinate Diocesan Synods. The bishops are elected as vacancies
arise, and, with certain restrictions, by the Diocesan Synods, the
Primate, whose see is Armagh, being chosen by the bishops out of their
own number. The patronage of benefices is vested in boards of
nomination, on which both the diocese and the parish are represented.
The Diocesan Courts, consisting of the bishop, his chancellor, and two
elected members, one clerical and the other lay, deal as courts of first
instance with legal questions; but there is an appeal to the Court of
the General Synod, composed of three bishops and four laymen who have
held judicial office. During the years 1871 to 1878 the revision of the
Prayer Book mainly occupied the attention of the General Synod; but
although many far-reaching resolutions were proposed by the then
predominant Evangelical party, few changes of moment were carried, and
none which affected the Church's doctrinal position. A two-thirds
majority of both the lay and clerical vote is necessary before any
change can be made in the formularies, and an ultimate veto rests, on
certain conditions, with the house of bishops.
The effects of Disestablishment have been partly good and partly evil.
On the one hand, the Church has now all the benefits of autonomy and is
free from the anomalies incidental to state control. Her laws are
definite, and the authority of her judicial courts is recognized by all
her members. The place given to the laity in her synods has quickened in
them the sense of responsibility so essential to the Church's progress.
And although there are few worldly inducements to men to take orders in
Ireland, the clergy are, for the most part, the equals of their
predecessors in social standing and in intellectual equipment, while the
standard of clerical activity is higher than in pre-Disestablishment
days. On the other hand, the vesting of patronage in large bodies like
synods, or (as is the case in some districts) in nominators with little
knowledge of the Church beyond the borders of their own parish, is not
an ideal system, although it is working better as the dangers of
parochialism and provinciality are becoming more generally recognized
than in the early years of Disestablishment.
The finances are controlled by the Representative Church Body, to which
the sum of L7,581,075, sufficient to provide life annuities for the
existing clergy (2043 in number), amounting to L596,913, was handed over
by the Church Temporalities Commissioners in 1870. So skilfully was this
fund administered, and so generous were the contributions of clergy and
laity, at and since Disestablishment, that while on 31st December 1906
only 136 annuitants were living, the total assets in the custody of the
Representative Church Body amounted at that date to L8,729,941. Of this
sum no less than L6,525,952 represented the free-will offerings of the
members of the Church for the thirty-seven years ending 31st December
1906. Out of the interest on capital, augmented by the annual parochial
assessments, which are administered by the central office, provision has
to be made for two archbishops at L2500 per annum, eleven bishops, who
receive about L1500 each, and over 1500 parochial clergy. Of the clergy
only 338 are curates, while 1161 are incumbents, the average annual
income of a benefice being about L240, with (in most cases) a house. The
large majority of the clergy receive their training in the Divinity
School of Trinity College, Dublin. At the census of 1901 the members of
the Church of Ireland numbered 579,385 out of a total population of
4,456,546.
See R. Mant, _History of the Church of Ireland_ (2 vols., London,
1840); _Essays on the Irish Church_, by various writers (Oxford,
1866); Maziere Brady, _The Alleged Conversion of the Irish Bishops_
(London, 1877); A. T. Lee, _The Irish Episcopal Succession_ (Dublin,
1867); G. T. Stokes, _Ireland and the Celtic Church_ (London, 1888),
_Ireland and the Anglo-Norman Church_ (London, 1892), _Some Worthies
of the Irish Church_ (London, 1900); T. Olden, _The Church of Ireland_
(London, 1892); J. T. Ball, _The Reformed Church of Ireland_ (London,
1890); H. C. Groves, _The Titular Archbishops of Ireland_ (Dublin,
1897); W. Lawlor, _The Reformation in Ireland_ (London, 1906);
_Reports of the Representative Church Body_ (Dublin, 1872-1905).
(J. H. Be.)
IRENAEUS, bishop of Lyons at the end of the 2nd century, was one of the
most distinguished theologians of the ante-Nicene Church. Very little is
known of his early history. His childhood was spent in Asia Minor,
probably at or near Smyrna; for he himself tells us (_Adv. haer._ iii.
3, 4, and Euseb. _Hist. Eccl._ v. 20) that as a child he heard the
preaching of Polycarp, the aged bishop of Smyrna (d. February 22, 156).
But we do not know when this was. He can hardly have been born very long
after 130, for later on he frequently mentions having met certain
Christian presbyters who had actually seen John, the disciple of our
Lord. The circumstances under which he came into the West are also
unknown to us; the only thing which is certain is that at the time of
the persecution of the Gallic Church under Marcus Aurelius (177) he was
a presbyter of the church at Lyons. In 177 or 178 he went to Rome on a
mission from this church, to make representations to Bishop Eleutherius
in favour of a more lenient treatment of the Montanists (see MONTANISM.;
Eus. v. 4. 2). On his return he was called upon to undertake the
direction of the church at Lyons in the place of Bishop Pothinus, who
had perished in the persecution (Eus. v. 5. 8). As bishop he carried on
a great and fruitful work. Though the statement of Gregory of Tours
(_Hist. Franc._ i. 29), that within a short time he succeeded in
converting all Lyons to Christianity, is probably exaggerated, from him
at any rate dates the wide spread of Christianity in Lyons and its
neighbourhood. He devoted particular attention to trying to reconcile
the numerous sects which menaced the existence of the church (see
below). In the dispute on the question of Easter, which for a long time
disturbed the Christian Church both in West and East, he endeavoured by
means of many letters to effect a compromise, and in particular to
exercise a moderating influence on Victor, the bishop of Rome, and his
unyielding attitude towards the dissentient churches of Africa, thus
justifying his name of "peace-maker" (Eirenaios) (Eus. _H. E._ v. 24.
28). The date of his death is unknown. His martyrdom under Septimius
Severus is related by Gregory of Tours, but by no earlier writer.
The chief work of Irenaeus, written about 180, is his "Refutation and
Overthrow of Gnosis, falsely so called" (usually indicated by the name
_Against the Heresies_). Of the Greek original of this work only
fragments survive; it only exists in full in an old Latin translation,
the slavish fidelity of which to a certain extent makes up for the loss
of the original text. The treatise is divided into five books: of these
the first two contain a minute and well-informed description and
criticism of the tenets of various heretical sects, especially the
Valentinians; the other three set forth the true doctrines of
Christianity, and it is from them that we find out the theological
opinions of the author. Irenaeus admits himself that he is not a good
writer. And indeed, as he worked, his materials assumed such
unmanageable proportions that he could not succeed in throwing them
into a satisfactory form. But however clumsily he may have handled his
material, he has produced a work which is even nowadays rightly valued
as the first systematic exposition of Catholic belief. The foundation
upon which Irenaeus bases his system consists in the episcopate, the
canon of the Old and New Testaments, and the rule of faith. With their
assistance he sets forth and upholds, in opposition to the gnostic
dualism, i.e. the severing of the natural and the supernatural, the
Catholic monism, i.e. the unity of the life of faith as willed by God.
The "grace of truth" (the _charisma_), which the apostles had called
down upon their first disciples by prayer and laying-on of hands, and
which was to be imparted anew by way of succession ([Greek: diadoche],
_successio_) to the bishops from generation to generation without a
break, makes those who receive it living witnesses of the salvation
offered to the faithful by written and spoken tradition. The Scriptures
of the Old and New Testaments, rightly expounded by the church alone,
give us an insight into God's plan of salvation for mankind, and explain
to us the covenant which He made on various occasions (Moses and Christ;
or Noah, Abraham, Moses and Christ). Finally, the "rule of faith"
(_regula fidei_), received at baptism, contains in itself all the riches
of Christian truth. To distribute these, i.e. to elucidate the rule of
faith as set forth in the creed, and further to point out its agreement
with the Scriptures, is the object of Irenaeus as a theologian. Hence he
lays the greatest stress on the conception of God's disposition of
salvation towards mankind (_oeconomia_), the object of which is that
mankind, who in Adam were sunk in sin and death, should in Christ,
comprised as it were in his person, be brought back to life. God, as the
head of the family, so to speak, disposes of all. The Son, the Word
(_Logos_) for ever dwelling with the Father, carries out His behests.
The Holy Ghost (_Pneuma_), however, as the Spirit of wisdom for ever
dwelling with the Father, controls what the Father has appointed and the
Son fulfilled, and this Spirit lives in the church. The climax of the
divine plan of salvation is found in the incarnation of the Word. God
was to become man, and in Christ he became man. Christ must be God; for
if not, the devil would have had a natural claim on him, and he would
have been no more exempt from death than the other children of Adam; he
must be _man_, if his blood were indeed to redeem us. On God incarnate
the power of the devil is broken, and in Him is accomplished the
reconciliation between God and man, who henceforth pursues his true
object, namely, to become like unto God. In the God-man God has drawn
men up to Himself. Into their human, fleshly and perishable nature
imperishable life is thereby engrafted; it has become deified, and death
has been changed into immortality. In the sacrament of the Lord's Supper
it is the heavenly body of the God-man which is actually partaken of in
the elements. This exposition by Irenaeus of the divine economy and the
incarnation was taken as a criterion by later theologians, especially in
the Greek Church (cf. Athanasius, Gregory of Nyssa, Cyril of Alexandria,
John of Damascus). He himself was especially influenced by St John and
St Paul. Before him the Fourth Gospel did not seem to exist for the
Church; Irenaeus made it a living force. His conception of the Logos is
not that of the philosophers and apologists; he looks upon the Logos not
as the "reason" of God, but as the "voice" with which the Father speaks
in the revelation to mankind, as did the writer of the Fourth Gospel.
And the Pauline epistles are adopted almost bodily by Irenaeus,
according to the ideas contained in them; his expositions often present
the appearance of a patchwork of St Paul's ideas. Certainly, it is only
one side of Paul's thought that he displays to us. The great conceptions
of justification and atonement are hardly ever touched by Irenaeus. In
Irenaeus is no longer heard the Jew, striving about and against the law,
who has had to break free from his early tradition of Pharisaism.
Till recent times whatever other writings and letters of Irenaeus are
mentioned by Eusebius appeared to be lost, with the exception of a
fragment here or there. Recently, however, two Armenian scholars,
Karapet Ter-Mekerttschian and Erwand Ter-Minassianz, have published
from an Armenian translation a German edition (Leipzig, 1907; minor
edition 1908) of the work "in proof of the apostolic teaching" mentioned
by Eusebius _(H. E._ v. 26). This work, which is in the form of a
dialogue with one Marcianus, otherwise unknown to us, contains a
statement of the fundamental truths of Christianity. It is the oldest
catechism extant, and an excellent example of how Bishop Irenaeus was
able not only to defend Christianity as a theologian and expound it
theoretically, but also to preach it to laymen.
BIBLIOGRAPHY.--The edition of the Benedictine R. Massuet (Paris, 1710
and 1734, reprinted in Migne, _Cursus patrologiae_, Series Graeca,
vol. v., Paris, 1857) long continued to be the standard one, till it
was superseded by the editions of Adolph Stieren (2 vols., Leipzig,
1848-1853) and of W. Wigan Harvey (2 vols., Cambridge, 1857), the
latter being the only edition which contains the Syriac fragments. For
an English translation see the _Ante-Nicene Library_. Of modern
monographs consult H. Ziegler, _Irenaeus, der Bischof von Lyon_
(Berlin, 1871); Friedrich Loofs, _Irenaeus-Handschriften_ (Leipzig,
1888); Johannes Werner, _Der Paulinismus des Irenaeus_ (Leipzig,
1889); Johannes Kunze, _Die Gotteslehre des Irenaeus_ (Leipzig, 1891);
Ernst Klebba, _Die Anthropologie des heiligen Irenaeus_ (Munster,
1894); Albert Dufourcq, _Saint Irenee_ (Paris, 1904); Franz Stoll,
_Die Lehre des Heil. Irenaeus von der Erlosung und Heiligung_ (Mainz,
1905); also the histories of dogma, especially Harnack, and
Bethune-Baker, _An Introduction to the Early History of Christian
Doctrine_ (London, 1903). (G. K.)
IRENE, the name of several Byzantine empresses.
1. IRENE (752-803), the wife of Leo IV., East Roman emperor. Originally
a poor but beautiful Athenian orphan, she speedily gained the love and
confidence of her feeble husband, and at his death in 780 was left by
him sole guardian of the empire and of their ten-year-old son
Constantine VI. Seizing the supreme power in the name of the latter,
Irene ruled the empire at her own discretion for ten years, displaying
great firmness and sagacity in her government. Her most notable act was
the restoration of the orthodox image-worship, a policy which she always
had secretly favoured, though compelled to abjure it in her husband's
lifetime. Having elected Tarasius, one of her partisans, to the
patriarchate (784), she summoned two church councils. The former of
these, held in 786 at Constantinople, was frustrated by the opposition
of the soldiers. The second, convened at Nicaea in 787, formally revived
the adoration of images and reunited the Eastern church with that of
Rome. As Constantine approached maturity he began to grow restive under
her autocratic sway. An attempt to free himself by force was met and
crushed by the empress, who demanded that the oath of fidelity should
thenceforward be taken in her name alone. The discontent which this
occasioned swelled in 790 into open resistance, and the soldiers, headed
by the Armenian guard, formally proclaimed Constantine VI. as the sole
ruler. A hollow semblance of friendship was maintained between
Constantine and Irene, whose title of empress was confirmed in 792; but
the rival factions remained, and Irene, by skilful intrigues with the
bishops and courtiers, organized a powerful conspiracy on her own
behalf. Constantine could only flee for aid to the provinces, but even
there he was surrounded by participants in the plot. Seized by his
attendants on the Asiatic shore of the Bosporus, the emperor was carried
back to the palace at Constantinople; and there, by the orders of his
mother, his eyes were stabbed out. An eclipse of the sun and a darkness
of seventeen days' duration were attributed by the common superstition
to the horror of heaven. Irene reigned in prosperity and splendour for
five years. She is said to have endeavoured to negotiate a marriage
between herself and Charlemagne; but according to Theophanes, who alone
mentions it, the scheme was frustrated by Aetius, one of her favourites.
A projected alliance between Constantine and Charlemagne's daughter,
Rothrude, was in turn broken off by Irene. In 802 the patricians, upon
whom she had lavished every honour and favour, conspired against her,
and placed on the throne Nicephorus, the minister of finance. The
haughty and unscrupulous princess, "who never lost sight of political
power in the height of her religious zeal," was exiled to Lesbos and
forced to support herself by spinning. She died the following year. Her
zeal in restoring images and monasteries has given her a place among
the saints of the Greek church.
See E. Gibbon, _The Decline and Fall of the Roman Empire_ (ed. J.
Bury, London, 1896), vol. v.; G. Finlay, _History of Greece_ (ed.
1877, Oxford,) vol. ii.; F. C. Schlosser, _Geschichte der
bildersturmenden Kaiser des ostromischen Reiches_ (Frankfort, 1812);
J. D. Phoropoulos, [Greek: Eirene he autokrateira Rhomaion] (Leipzig,
1887); J. B. Bury, _The Later Roman Empire_ (London, 1889), ii.
480-498; C. Diehl, _Figures byzantines_ (Paris, 1906), pp. 77-109.
(M. O. B. C.)
2. IRENE (c. 1066-c. 1120), the wife of Alexius I. The best-known fact
of her life is the unsuccessful intrigue by which she endeavoured to
divert the succession from her son John to Nicephorus Bryennius, the
husband of her daughter Anna. Having failed to persuade Alexius, or,
upon his death, to carry out a _coup d'etat_ with the help of the palace
guards, she retired to a monastery and ended her life in obscurity.
3. IRENE (d. 1161), the first wife of Manuel Comnenus. She was the
daughter of the count of Sulzbach, and sister-in-law of the Roman
emperor Conrad II., who arranged her betrothal. The marriage was
celebrated at Constantinople in 1146. The new empress, who had exchanged
her earlier name of Bertha for one more familiar to the Greeks, became a
devoted wife, and by the simplicity of her manner contrasted favourably
with most Byzantine queens of the age.
H. v. Kap-Herr, _Die abendlandische Politik des Kaisers Manuel_
(Strassburg, 1881).
IRETON, HENRY (1611-1651), English parliamentary general, eldest son of
German Ireton of Attenborough, Nottinghamshire, was baptized on the 3rd
of November 1611, became a gentleman commoner of Trinity College,
Oxford, in 1626, graduated B.A. in 1629, and entered the Middle Temple
the same year. On the outbreak of the Civil War he joined the
parliamentary army, fought at Edgehill and at Gainsborough in July 1643,
was made by Cromwell deputy-governor of the Isle of Ely, and next year
served under Manchester in the Yorkshire campaign and at the second
battle of Newbury, afterwards supporting Cromwell in his accusations of
incompetency against the general. On the night before the battle of
Naseby, in June 1645, he succeeded in surprising the Royalist army and
captured many prisoners, and next day, on the suggestion of Cromwell, he
was made commissary-general and appointed to the command of the left
wing, Cromwell himself commanding the right. The wing under Ireton was
completely broken by the impetuous charge of Rupert, and Ireton was
wounded and taken prisoner, but after the rout of the enemy which ensued
on the successful charge of Cromwell he regained his freedom. He was
present at the siege of Bristol in the September following, and took an
active part in the subsequent victorious campaign which resulted in the
overthrow of the royal cause. On the 30th of October 1645 Ireton entered
parliament as member for Appleby, and while occupied with the siege of
Oxford he was, on the 15th of June 1646, married to Bridget, daughter of
Oliver Cromwell. This union brought Ireton into still closer connexion
with Cromwell, with whose career he was now more completely identified.
But while Cromwell's policy was practically limited to making the best
of the present situation, and was generally inclined to compromise,
Ireton's attitude was based on well-grounded principles of
statesmanship. He was opposed to the destructive schemes of the extreme
party, disliked especially the abstract and unpractical theories of the
Republicans and the Levellers, and desired, while modifying their mutual
powers, to retain the constitution of King, Lords and Commons. He urged
these views in the negotiations of the army with the parliament, and in
the conferences with the king, being the person chiefly entrusted with
the drawing up of the army proposals, including the manifesto called
"The Heads of the Proposals." He endeavoured to prevent the breach
between the army and the parliament, but when the division became
inevitable took the side of the former. He persevered in supporting the
negotiations with the king till his action aroused great suspicion and
unpopularity. He became at length convinced of the hopelessness of
dealing with Charles, and after the king's flight to the Isle of Wight
treated his further proposals with coldness and urged the parliament to
establish an administration without him. Ireton served under Fairfax in
the second civil war in the campaigns in Kent and Essex, and was
responsible for the executions of Lucas and Lisle at Colchester. After
the rejection by the king of the last offers of the army, he showed
special zeal in bringing about his trial, was one of the chief promoters
of "Pride's Purge," attended the court regularly, and signed the
death-warrant. The regiment of Ireton having been chosen by lot to
accompany Cromwell in his Irish campaign, Ireton was appointed
major-general; and on the recall of his chief to take the command in
Scotland, he remained with the title and powers of lord-deputy to
complete Cromwell's work of reduction and replantation. This he
proceeded to do with his usual energy, and as much by the severity of
his methods of punishment as by his military skill was rapidly bringing
his task to a close, when he died on the 26th of November 1651 of fever
after the capture of Limerick. His loss "struck a great sadness into
Cromwell," and perhaps there was no one of the parliamentary leaders who
could have been less spared, for while he possessed very high abilities
as a soldier, and great political penetration and insight, he resembled
in stern unflinchingness of purpose the protector himself. By his wife,
Bridget Cromwell, who married afterwards General Charles Fleetwood,
Ireton left one son and three daughters.
BIBLIOGRAPHY.--Article by C. H Firth in _Dict. of Nat. Biog._ with
authorities there quoted; Wood's _Ath. Oxon._ iii. 298, and _Fasti_,
i. 451; Cornelius Brown's _Lives of Notts Worthies_, 181; _Clarke
Papers_ published by Camden Society; Gardiner's _History of the Civil
War and of the Commonwealth_.
IRIARTE (or YRIARTE) Y OROPESA, TOMAS DE (1750-1791), Spanish poet, was
born on the 18th of September 1750, at Orotava in the island of
Teneriffe, and received his literary education at Madrid under the care
of his uncle, Juan de Iriarte, librarian to the king of Spain. In his
eighteenth year the nephew began his literary career by translating
French plays for the royal theatre, and in 1770, under the anagram of
Tirso Imarete, he published an original comedy entitled _Hacer que
hacemos_. In the following year he became official translator at the
foreign office, and in 1776 keeper of the records in the war department.
In 1780 appeared a dull didactic poem in _silvas_ entitled _La Musica_,
which attracted some attention in Italy as well as at home. The _Fabulas
literarias_ (1781), with which his name is most intimately associated,
are composed in a great variety of metres, and show considerable
ingenuity in their humorous attacks on literary men and methods; but
their merits have been greatly exaggerated. During his later years,
partly in consequence of the _Fabulas_, Iriarte was absorbed in personal
controversies, and in 1786 was reported to the Inquisition for his
sympathies with the French philosophers. He died on the 17th of
September 1791.
He is the subject of an exhaustive monograph (1897) by Emilio Cotarelo
y Mori.
IRIDACEAE (the iris family), in botany, a natural order of flowering
plants belonging to the series Liliiflorae of the class Monocotyledons,
containing about 800 species in 57 genera, and widely distributed in
temperate and tropical regions. The members of this order are generally
perennial herbs growing from a corm as in _Crocus_ and _Gladiolus_, or a
rhizome as in _Iris_; more rarely, as in the Spanish iris, from a bulb.
A few South African representatives have a shrubby habit. The flowers
are hermaphrodite and regular as in _Iris_ (fig. 1) and _Crocus_ (fig.
3), or with a symmetry in the median plane as in _Gladiolus_. The
petaloid perianth consists of two series, each with three members, which
are joined below into a longer or shorter tube, followed by one whorl of
three stamens; the inferior ovary is three-celled and contains numerous
ovules on an axile placenta; the style is branched and the branches are
often petaloid. The fruit (fig. 2) is a capsule opening between the
partitions and containing generally a large number of roundish or
angular seeds. The arrangement of the parts in the flower resembles that
in the nearly allied order Amaryllidaceae (_Narcissus_, _Snowdrop_,
&c.), but differs in the absence of the inner whorl of stamens.
[Illustration: FIG. 1.--Yellow Iris, _Iris Pseudacorus_.
1. Flower, from which the outer petals and the stigmas have been
removed, leaving the inner petals (a) and stamens.
2. Pistil with petaloid stigmas.
3. Fruit cut across showing the three chambers containing seeds.
4. A seed. 1-4 about 1/2 nat. size.]
[Illustration: FIG. 2.--Seed-vessel (capsule) of the Flower-de-Luce
(_iris_), opening in a loculicidal manner. The three valves bear the
septa in the centre and the opening takes place through the back of the
chambers. Each valve is formed by the halves of contiguous carpels.]
[Illustration: FIG. 3.--1. Crocus in flower, reduced. 2. Flower
dissected. b, b', Upper and lower membranous spathe-like bracts; c, Tube
of perianth; d, Ovary; e, Style; f, Stigmas.]
The most important genera are _Crocus_ (q.v.), with about 70 species,
_Iris_ (q.v.), with about 100, and _Gladiolus_ (q.v.), with 150. _Ixia_,
_Freesia_ (q.v.) and _Tritonia_ (including _Montbretia_), all natives of
South Africa, are well known in cultivation. _Sisyrinchium_, blue-eyed
grass, is a new-world genus extending from arctic America to Patagonia
and the Falkland Isles. One species, _S. angustifolium_, an arctic and
temperate North American species, is also native in Galway and Kerry in
Ireland. Other British representatives of the order are: _Iris
Pseudacorus_, (yellow iris), common by river-banks and ditches, _I.
foetidissima (stinking iris), _Gladiolus communis_, a rare plant found
in the New Forest and the Isle of Wight, and _Romulea Columnae_, a small
plant with narrow recurved leaves a few inches long and a short scape
bearing one or more small regular funnel-shaped flowers, which occurs at
Dawlish in Devonshire.
IRIDIUM (symbol Ir.; atomic weight 193.1), one of the metals of the
platinum group, discovered in 1802 by Smithson Tennant during the
examination of the residue left when platinum ores are dissolved in
_aqua regia_; the element occurs in platinum ores in the form of alloys
of platinum and iridium, and of osmium and iridium. Many methods have
been devised for the separation of these metals (see PLATINUM), one of
the best being that of H. St. C Deville and H. J. Debray (_Comptes
rendus_, 1874, 78, p. 1502). In this process the osmiridium is fused
with zinc and the excess of zinc evaporated; the residue is then ignited
with barium nitrate, extracted with water and boiled with nitric acid.
The iridium is then precipitated from the solution (as oxide) by the
addition of baryta, dissolved in _aqua regia_, and precipitated as
iridium ammonium chloride by the addition of ammonium chloride. The
double chloride is fused with nitre, the melt extracted with water and
the residue fused with lead, the excess of lead being finally removed by
solution in nitric acid and _aqua regia_. It is a brittle metal of
specific gravity 22.4 (Deville and Debray), and is only fusible with
great difficulty. It may be obtained in the spongy form by igniting
iridium ammonium chloride, and this variety of the metal readily
oxidizes when heated in air.
Two oxides of iridium are known, namely the _sesquioxide_, Ir2O3, and
the _dioxide_, IrO2, corresponding to which there are two series of
salts, the sesqui-salts and the iridic salts; a third series of salts
is also known (the iridious salts) derived from an oxide IrO. _Iridium
sesquioxide_, Ir2O3, is obtained when potassium iridium chloride is
heated with sodium or potassium carbonates, in a stream of carbon
dioxide. It is a bluish-black powder which at high temperatures
decomposes into the metal, dioxide and oxygen. The hydroxide, Ir(OH)3,
may be obtained by the addition of caustic potash to iridium sodium
chloride, the mixture being then heated with alcohol. _Iridium
dioxide_, IrO2, may be obtained as small needles by heating the metal
to bright redness in a current of oxygen (G. Geisenheimer, _Comptes
rendus_, 1890, 110, p. 855). The corresponding hydroxide, Ir(OH)4, is
formed when potassium iridate is boiled with ammonium chloride, or
when the tetrachloride is boiled with caustic potash or sodium
carbonate. It is an indigo-blue powder, soluble in hydrochloric acid,
but insoluble in dilute nitric and sulphuric acids. On the oxides see
L. Wohler and W. Witzmann, _Zeit. anorg. Chem._ (1908), 57, p. 323.
_Iridium sesquichloride_, IrCl3, is obtained when one of the
corresponding double chlorides is heated with concentrated sulphuric
acid, the mixture being then thrown into water. It is thus obtained as
an olive green precipitate which is insoluble in acids and alkalis.
_Potassium iridium sesquichloride_, K3IrCl6.3H2O, is obtained by
passing sulphur dioxide into a suspension of potassium chloriridate in
water until all dissolves, and then adding potassium carbonate to the
solution (C. Claus, _Jour. prak. Chem._, 1847, 42, p. 351). It forms
green prisms which are readily soluble in water. Similar sodium and
ammonium compounds are known. _Iridium tetrachloride_, IrCl4, is
obtained by dissolving the finely divided metal in _aqua regia_; by
dissolving the hydroxide in hydrochloric acid; and by digesting the
hydrated sesquichloride with nitric acid. On evaporating the solution
(not above 40 deg. C.) a dark mass is obtained, which contains a little
sesquichloride. It forms double chlorides with the alkaline chlorides.
For a bromide see A. Gautbier and M. Riess, _Ber._, 1909, 42, p. 3905.
_Iridium sulphide_, IrS, is obtained when the metal is ignited in
sulphur vapour. The _sesquisulphide_, Ir2S3, is obtained as a brown
precipitate when sulphuretted hydrogen is passed into a solution of
one of the sesqui-salts. It is slightly soluble in potassium sulphide.
The _disulphide_, IrS2, is formed when powdered iridium is heated with
sulphur and an alkaline carbonate. It is a dark brown powder. Iridium
forms many ammine derivatives, which are analogous to the
corresponding platinum compounds (see M. Skoblikoff, _Jahresb._, 1852,
p. 428; W. Palmer, _Ber._, 1889, 22, p. 15; 1890, 23, p. 3810; 1891,
24, p. 2090; _Zeit. anorg. Chem._, 1896, 13, p. 211).
Iridium is always determined quantitatively by conversion into the
metallic state. The atomic weight of the element has been determined
in various ways, C. Seubert (_Ber._, 1878, 11, p. 1770), by the
analysis of potassium chloriridate obtaining the value 192.74, and A.
Joly (_Comptes rendus_, 1890, 110, p. 1131) from analyses of potassium
and ammonium chloriridites, the value 191.78 (O = 15.88).
IRIGA, a town of the province of Ambos Camarines, Luzon, Philippine
Islands, on the Bicol river, about 20 m. S.E. of Nueva Caceres and near
the S.W. base of Mt. Iriga, a volcanic peak reaching a height of 4092
ft. above the sea. Pop. (1903) 19,297. Iriga has a temperate climate.
The soil in its vicinity is rich, producing rice, Indian corn, sugar,
pepper, cacao, cotton, abaca, tobacco and copra. The neighbouring
forests furnish ebony, molave, tindalo and other very valuable
hardwoods. The language is Bicol.
IRIS, in Greek mythology, daughter of Thaumas and the Ocean nymph
Electra (according to Hesiod), the personification of the rainbow and
messenger of the gods. As the rainbow unites earth and heaven, Iris is
the messenger of the gods to men; in this capacity she is mentioned
frequently in the _Iliad_, but never in the _Odyssey_, where Hermes
takes her place. She is represented as a youthful virgin, with wings of
gold, who hurries with the swiftness of the wind from one end of the
world to the other, into the depths of the sea and the underworld. She
is especially the messenger of Zeus and Hera, and is associated with
Hermes, whose caduceus or staff she often holds. By command of Zeus she
carries in a ewer water from the Styx, with which she puts to sleep all
who perjure themselves. Her attributes are the caduceus and a vase.
IRIS, in botany. The iris flower belongs to the natural order Iridaceae
of the class Monocotyledons, which is characterized by a petaloid
six-parted perianth, an inferior ovary and only three stamens (the outer
series), being thus distinguished from the Amaryllidaceae family, which
has six stamens. They are handsome showy-flowered plants, the Greek name
having been applied on account of the hues of the flowers. The genus
contains about 170 species widely distributed throughout the north
temperate zone. Two of the species are British. _I. Pseudacorus_, the
yellow flag or iris, is common in Britain on river-banks, and in marshes
and ditches. It is called the "water-flag" or "bastard floure de-luce"
by Gerard, who remarks that "although it be a water plant of nature, yet
being planted in gardens it prospereth well." Its flowers appear in June
and July, and are of a golden-yellow colour. The leaves are from 2 to 4
ft. long, and half an inch to an inch broad. Towards the latter part of
the year they are eaten by cattle. The seeds are numerous and
pale-brown; they have been recommended when roasted as a substitute for
coffee, of which, however, they have not the properties. The astringent
rhizome has diuretic, purgative and emetic properties, and may, it is
said, be used for dyeing black, and in the place of galls for
ink-making. The other British species, _I. foetidissima_, the fetid
iris, gladdon or roast-beef plant, the _Xyris_ or stinking gladdon of
Gerard, is a native of England south of Durham, and also of Ireland,
southern Europe and North Africa. Its flowers are usually of a dull,
leaden-blue colour; the capsules, which remain attached to the plant
throughout the winter, are 2 to 3 in. long; and the seeds scarlet. When
bruised this species emits a peculiar and disagreeable odour.
_Iris florentina_, with white or pale-blue flowers, is a native of the
south of Europe, and is the source of the violet-scented orris root used
in perfumery. _Iris versicolor_, or blue flag, is indigenous to North
America, and yields "iridin," a powerful hepatic stimulant. _Iris
germanica_ of central Europe, "the most common purple Fleur de Luce" of
Ray, is the large common blue iris of gardens, the bearded iris or fleur
de luce and probably the Illyrian iris of the ancients. From the flowers
of _Iris florentina_ a pigment--the "verdelis," "vert d'iris," or
iris-green, formerly used by miniature painters--was prepared by
maceration, the fluid being left to putrefy, when chalk or alum was
added. The garden plants known as the Spanish iris and the English iris
are both of Spanish origin, and have very showy flowers. Along with some
other species, as _I. reticulata_ and _I. persica_, both of which are
fragrant, they form great favourites with florists. All these just
mentioned differ from those formerly named in the nature of the
underground stem, which forms a bulb and not a strict creeping rhizome
as in _I. Pseudacorus_, _germanica_, _florentina_, &c. Some botanists
separate these bulbous irises from the genus _Iris_, and place them
apart in the genus _Xiphium_, the Spanish iris, including about 30
species, all from the Mediterranean region and the East.
[Illustration: FIG. 1.--Gynoecium of Iris, consisting of an inferior
ovary o, and a style, with three petaloid segments s, bearing stigmas
st.]
[Illustration: FIG. 2.--Diagram of Trimerous Symmetrical Flower of Iris,
with two whorls of perianth, three stamens in one whorl and an ovary
formed of three carpels. The three dots indicate the position of an
inner whorl of stamens which is present in the allied families
Amaryllidaceae and Liliaceae but absent in Iridaceae.]
The iris flower is of special interest as an example of the relation
between the shape of the flower and the position of the pollen-receiving
and stigmatic surfaces on the one hand and the visits of insects on the
other. The large outer petals form a landing-stage for a flying insect
which in probing the perianth-tube for honey will first come in contact
with the stigmatic surface which is borne on the outer face of a
shelf-like transverse projection on the under side of the petaloid
style-arm. The anther, which opens towards the outside, is sheltered
beneath the over-arching style arm below the stigma, so that the insect
comes in contact with its pollen-covered surface only after passing the
stigma, while in backing out of the flower it will come in contact only
with the non-receptive lower face of the stigma. Thus an insect bearing
pollen from one flower will in entering a second deposit the pollen on
the stigma, while in backing out of a flower the pollen which it bears
will not be rubbed off on the stigma of the same flower.
The hardier bulbous irises, including the Spanish iris (_I. Xiphium_)
and the English iris (_I. xiphioides_, so called, which is also of
Spanish origin), require to be planted in thoroughly drained beds in
very light open soil, moderately enriched, and should have a rather
sheltered position. Both these present a long series of beautiful
varieties of the most diverse colours, flowering in May, June and
July, the smaller Spanish iris being the earlier of the two. There are
many other smaller species of bulbous iris. Being liable to perish
from excess of moisture, they should have a well-drained bed of good
but porous soil made up for them, in some sunny spot, and in winter
should be protected by a 6-in. covering of half-decayed leaves or
fresh coco-fibre refuse. To this set belong _I. persica_,
_reticulata_, _filifolia_, _Histrio_, _juncea_, _Danfordiae_
_Rosenbachiana_ and others which flower as early as February and
March.
The flag irises are for the most part of the easiest culture; they
grow in any good free garden soil, the smaller and more delicate
species only needing the aid of turfy ingredients, either peaty or
loamy, to keep it light and open in texture. The earliest to bloom are
the dwarf forms of _Iris pumila_, which blossom during March, April
and May; and during the latter month and the following one most of the
larger growing species, such as _I. germanica_, _florentina_,
_pallida_, _variegata_, _amoena_, _flavescens_, _sambucina_,
_neglecta_, _ruthenica_, &c., produce their gorgeous flowers. Of many
of the foregoing there are, besides the typical form, a considerable
number of named garden varieties. _Iris unguicularis_ (or _stylosa_)
is a remarkable winter flowering species from Algeria, with sky-blue
flowers blotched with yellow, produced at irregular intervals from
November to March, the bleakest period of the year.
The beautiful Japanese _Iris Kaempferi_ (or _I. laevigata_) is of
comparatively modern introduction, and though of a distinct type is
equally beautiful with the better-known species. The outer segments
are rather spreading than deflexed, forming an almost circular flower,
which becomes quite so in some of the very remarkable duplex
varieties, in which six of these broad segments are produced instead
of three. Of this too there are numberless varieties cultivated under
names. They require a sandy peat soil on a cool moist subsoil.
What are known as _Oncocyclus_, or cushion irises, constitute a
magnificent group of plants remarkable for their large, showy and
beautifully marked flowers. Compared with other irises the "cushion"
varieties are scantily furnished with narrow sickle-shaped leaves and
the blossoms are usually borne singly on the stalks. The best-known
kinds are _atrofusca_, _Barnumae_, _Bismarckiana_, _Gatesi_,
_Heylandiana_, _iberica_, _Lorteti_, _Haynei_, _lupina_, _Mariae_,
_meda_, _paradoxa_, _sari_, _sofarana_ and _susiana_--the last-named
being popularly called the "mourning" iris owing to the dark silvery
appearance of its huge flowers. All these cushion irises are somewhat
fastidious growers, and to be successful with them they must be
planted rather shallow in very gritty well-drained soil. They should
not be disturbed in the autumn, and after the leaves have withered the
roots should be protected from heavy rains until growth starts again
naturally.
A closely allied group to the cushion irises are those known as
_Regelia_, of which _Korolkowi_, _Leichtlini_ and _vaga_ are the best
known. Some magnificent hybrids have been raised between these two
groups, and a hardier and more easily grown race of garden irises has
been produced under the name of _Regelio-Cyclus_. They are best
planted in September or October in warm sunny positions, the rhizomes
being lifted the following July after the leaves have withered.
IRISH MOSS, or CARRAGEEN (Irish _carraigeen_, "moss of the rock"), a
sea-weed (_Chondrus crispus_) which grows abundantly along the rocky
parts of the Atlantic coast of Europe and North America. In its fresh
condition the plant is soft and cartilaginous, varying in colour from a
greenish-yellow to a dark purple or purplish-brown; but when washed and
sun-dried for preservation it has a yellowish translucent horn-like
aspect and consistency. The principal constituent of Irish moss is a
mucilaginous body, of which it contains about 55%; and with that it has
nearly 10% of albuminoids and about 15% of mineral matter rich in iodine
and sulphur. When softened in water it has a sea-like odour, and from
the abundance of its mucilage it will form a jelly on boiling with from
20 to 30 times its weight of water. The jelly of Irish moss is used as
an occasional article of food. It may also be used as a thickener in
calico-printing and for fining beer. Irish moss is frequently mixed with
_Gigartina mammillosa_, _G. acicularis_ and other sea-weeds with which
it is associated in growth.
IRKUTSK, a government of Asiatic Russia, in East Siberia, bounded on the
W. by the government of Yeniseisk, on the N. by Yakutsk, on the E. by
Lake Baikal and Transbaikalia and on the S. and S.W. by Mongolia; area,
287,061 sq. m. The most populous region is a belt of plains 1200 to 2000
ft. in altitude, which stretch north-west to south-east, having the
Sayan mountains on the south and the Baikal mountains on the north, and
narrowing as it approaches the town of Irkutsk. The high road, now the
Trans-Siberian railway, follows this belt. The south-western part of the
government is occupied by mountains of the Sayan system, whose exact
orography is as yet not well known. From the high plateau of Mongolia,
fringed by the Sayan mountains, of which the culminating point is the
snow-clad Munko-sardyk (11,150 ft.), a number of ranges, 7500 to 8500
ft. high, strike off in a north-east direction. Going from south to
north they are distinguished as the Tunka Alps, the Kitoi Alps (both
snow-clad nearly all the year round), the Ida mountains and the Kuitun
mountains. These are, however, by no means regular chains, but on the
contrary are a complex result of upheavals which took place at different
geological epochs, and of denudation on a colossal scale. A beautiful,
fertile valley, drained by the river Irkut, stretches between the Tunka
Alps and the Sayan, and another somewhat higher plain, but not so wide,
stretches along the river Kitoi. A succession of high plains, 2000 to
2500 ft. in altitude, formed of horizontal beds of Devonian (or Upper
Silurian) sandstone and limestone, extends to the north of the railway
along the Angara, or Verkhnyaya (i.e. upper) Tunguzka, and the upper
Lena, as far as Kirensk. The Bratskaya Steppe, west of the Angara, is a
prairie peopled by Buriats. A mountain region, usually described as the
Baikal range, but consisting in reality of several ranges running
north-eastwards, across Lake Baikal, and scooped out to form the
depression occupied by the lake, is fringed on its north-western slope
by horizontal beds of sandstone and limestone. Farther north-east the
space between the Lena and the Vitim is occupied by another mountain
region belonging to the Olekma and Vitim system, composed of several
parallel mountain chains running north-eastwards (across the lower
Vitim), and auriferous in the drainage area of the Mama (N.E. of Lake
Baikal). Lake Baikal separates Irkutsk from Transbaikalia. The principal
rivers of the government are the Angara, which flows from this lake
northwards, with numerous sharp windings, and receives from the left
several large tributaries. as the Irkut, Kitoi, Byelaya, Oka and Iya.
The Lena is the principal means of communication both with the
gold-mines on its own tributary, the lower Vitim, and with the province
of Yakutsk. The Nizhnyaya Tunguzka flows northwards, to join the Yenisei
in the far north, and the mountain streams tributary to the Vitim drain
the north-east.
The post-Tertiary formations are represented by glacial deposits in
the highlands and loess on their borders. Jurassic deposits are met
with in a zone running north-westwards from Lake Baikal to
Nizhne-udinsk. The remainder of this region is covered by vast series
of Carboniferous, Devonian and Silurian deposits--the first two but
slightly disturbed over wide areas. All the highlands are built up of
older, semi-crystalline Cambro-Silurian strata, which attain a
thickness of 2500 ft., and of crystalline slates and limestones of the
Laurentian system, with granites, syenites, diorites and diabases
protruding from beneath them. Very extensive beds of basaltic lavas
and other volcanic deposits are spread along the border ridge of the
high plateau, about Munko-sardyk, up the Irkut, and on the upper Oka,
where cones of extinct volcanoes are found (Jun-bulak). Earthquakes
are frequent in the neighbourhood of Lake Baikal and the surrounding
region. Gold is extracted in the Nizhne-udinsk district; graphite is
found on the Botu-gol and Alibert mountains (abandoned many years
since) and on the Olkhon island of Lake Baikal. Brown coal (Jurassic)
is found in many places, and coal on the Oka. The salt springs of
Usoliye (45 m. west of Irkutsk), as also those on the Ilim and of
Ust-Kutsk (on the Lena), yield annually about 7000 tons of salt.
Fireclay, grindstones, marble and mica, lapis-lazuli, granites and
various semi-precious stones occur on the Sludyanka (south-west corner
of the Baikal).
The climate is severe; the mean temperatures being at Irkutsk (1520
ft), for the year 31 deg. Fahr., for January -6 deg., for July 65
deg.; at Shimki (valley of the Irkut, 2620 ft.), for the year 24 deg.,
for January -17 deg., for July 63 deg. The average rainfall is 15 in.
a year. Virgin forests cover all the highlands up to 6500 ft.
The population which was 383,578 in 1879, was 515,132 in 1897, of whom
238,997 were women and 60,396 were urban; except about 109,000 Buriats
and 1700 Tunguses, they are Russians. The estimated population in 1906
was 552,700. Immigration contributes about 14,000 every year. Schools
are numerous at Irkutsk, but quite insufficient in the country
districts, and only 12% of the children receive education. The soil is
very fertile in certain parts, but meagre elsewhere, and less than a
million acres are under crops (rye, wheat, barley, oats, buckwheat,
potatoes). Grain has to be imported from West Siberia and cattle from
Transbaikalia. Fisheries on Lake Baikal supply every year about
2,400,000 Baikal herring (_omul_). Industry is only beginning to be
developed (iron-works, glass- and pottery-works and distilleries, and
all manufactured goods are imported from Russia). The government is
divided into five districts, the chief towns of which are Irkutsk
(q.v.), Balagansk (pop., 1313 in 1897), Kirensk (2253), Nizhne-udinsk
and Verkholensk. (P. A. K.; J. T. Be.)
IRKUTSK, the chief town of the above government, is the most important
place in Siberia, being not only the largest centre of population and
the principal commercial depot north of Tashkent, but a fortified
military post, an archbishopric of the Orthodox Greek Church and the
seat of several learned societies. It is situated in 52 deg. 17' N. and
104 deg. 16' E., 3792 m. by rail from St Petersburg. Pop. (1875) 32,512,
(1900) 49,106. The town proper lies on the right bank of the Angara, a
tributary of the Yenisei, 45 m. below its outflow from Lake Baikal, and
on the opposite bank is the Glaskovsk suburb. The river, which has a
breadth of 1900 ft., is crossed by a flying bridge. The Irkut, from
which the town takes its name, is a small river which joins the Angara
directly opposite the town, the main portion of which is separated from
the monastery, the castle, the port and the suburbs by another
confluent, the Ida or Ushakovka. Irkutsk has long been reputed a
remarkably fine city--its streets being straight, broad, well paved and
well lighted; but in 1879, on the 4th and 6th of July, the palace of the
(then) governor-general, the principal administrative and municipal
offices and many of the other public buildings were destroyed by fire;
and the government archives, the library and museum of the Siberian
section of the Russian Geographical Society were utterly ruined. A
cathedral (built of wood in 1693 and rebuilt of stone in 1718), the
governor's palace, a school of medicine, a museum, a military hospital,
and the crown factories are among the public institutions and
buildings. An important fair is held in December. Irkutsk grew out of
the winter-quarters established (1652) by Ivan Pokhabov for the
collection of the fur tax from the Buriats. Its existence as a town
dates from 1686.
IRMIN, or IRMINUS, in Teutonic mythology, a deified eponymic hero of the
Herminones. The chief seat of his worship was Irminsal, or Ermensul, in
Westphalia, destroyed in 772 by Charlemagne. Huge wooden posts (Irmin
pillars) were raised to his honour, and were regarded as sacred by the
Saxons.
IRNERIUS (Hirnerius, Hyrnerius, Iernerius, Gernerius, Guarnerius,
Warnerius, Wernerius, Yrnerius), Italian jurist, sometimes referred to
as "lucerna juris." He taught the "free arts" at Bologna, his native
city, during the earlier decades of the 12th century. Of his personal
history nothing is known, except that it was at the instance of the
countess Matilda, Hildebrand's friend, who died in 1115, that he
directed his attention and that of his students to the _Institutes_ and
_Code_ of Justinian; that after 1116 he appears to have held some office
under the emperor Henry V.; and that he died, perhaps during the reign
of the emperor Lothair II., but certainly before 1140. He was the first
of the Glossators (see GLOSS), and according to ancient opinion (which,
however, has been much controverted) was the author of the epitome of
the _Novellae_ of Justinian, called the _Authentica_, arranged according
to the titles of the _Code_. His _Formularium tabellionum_ (a directory
for notaries) and _Quaestiones_ (a book of decisions) are no longer
extant. (See ROMAN LAW.)
See Savigny, _Gesch. d. rom. Rechts im Mittelalter_, iii. 83; Vecchio,
_Notizie di Irnerio e della sua scuola_ (Pisa, 1869); Ficker, _Forsch,
z. Reichs- u. Rechtsgesch. Italiens_, vol. iii. (Innsbruck, 1870); and
Fitting, _Die Anfange der Rechtsschule zu Bologna_ (Berlin, 1888).
IRON [symbol Fe, atomic weight 55.85 (O = 16)], a metallic chemical
element. Although iron occurs only sparingly in the free state, the
abundance of ores from which it may be readily obtained led to its
application in the arts at a very remote period. It is generally agreed,
however, that the Iron Age, the period of civilization during which this
metal played an all-important part, succeeded the ages of copper and
bronze, notwithstanding the fact that the extraction of these metals
required greater metallurgical skill. The Assyrians and Egyptians made
considerable use of the metal; and in Genesis iv. 22 mention is made of
Tubal-cain as the instructor of workers in iron and copper. The earlier
sources of the ores appear to have been in India; the Greeks, however,
obtained it from the Chalybes, who dwelt on the south coast of the Black
Sea; and the Romans, besides drawing from these deposits, also exploited
Spain, Elba and the province of Noricum. (See METAL-WORK.)
The chief occurrences of metallic iron are as minute spiculae
disseminated through basaltic rocks, as at Giant's Causeway and in the
Auvergne, and, more particularly, in meteorites (q.v.). In combination
it occurs, usually in small quantity, in most natural waters, in plants,
and as a necessary constituent of blood. The economic sources are
treated under IRON AND STEEL below; in the same place will be found
accounts of the manufacture, properties, and uses of the metal, the
present article being confined to its chemistry. The principal iron ores
are the oxides and carbonates, and these readily yield the metal by
smelting with carbon. The metal so obtained invariably contains a
certain amount of carbon, free or combined, and the proportion and
condition regulate the properties of the metal, giving origin to the
three important varieties: cast iron, steel, wrought iron. The perfectly
pure metal may be prepared by heating the oxide or oxalate in a current
of hydrogen; when obtained at a low temperature it is a black powder
which oxidizes in air with incandescence; produced at higher
temperatures the metal is not pyrophoric. Peligot obtained it as minute
tetragonal octahedra and cubes by reducing ferrous chloride in hydrogen.
It may be obtained electrolytically from solutions of ferrous and
magnesium sulphates and sodium bicarbonate, a wrought iron anode and a
rotating cathode of copper, thinly silvered and iodized, being employed
(S. Maximowitsch, _Zeit. Elektrochem._, 1905, 11, p. 52).
In bulk, the metal has a silvery white lustre and takes a high polish.
Its specific gravity is 7.84; and the average specific heat over the
range 15 deg.-100 deg. is 0.10983; this value increases with temperature
to 850 deg., and then begins to diminish. It is the most tenacious of
all the ductile metals at ordinary temperatures with the exception of
cobalt and nickel; it becomes brittle, however, at the temperature of
liquid air. It softens at a red heat, and may be readily welded at a
white heat; above this point it becomes brittle. It fuses at about 1550
deg.-1600 deg., and may be distilled in the electric furnace (H.
Moissan, _Compt. rend._, 1906, 142, p. 425). It is attracted by a magnet
and may be magnetized, but the magnetization is quickly lost. The
variation of physical properties which attends iron on heating has led
to the view that the metal exists in allotropic forms (see IRON AND
STEEL, below).
Iron is very reactive chemically. Exposed to atmospheric influences it
is more or less rapidly corroded, giving the familiar rust (q.v.). S.
Burnie (_Abst. J.C.S._, 1907, ii. p. 469) has shown that water is
decomposed at all temperatures from 0 deg. to 100 deg. by the finely
divided metal with liberation of hydrogen, the action being accelerated
when oxides are present. The decomposition of steam by passing it
through a red-hot gun-barrel, resulting in the liberation of hydrogen
and the production of magnetic iron oxide, Fe3O4, is a familiar
laboratory method for preparing hydrogen (q.v.). When strongly heated
iron inflames in oxygen and in sulphur vapour; it also combines directly
with the halogens. It dissolves in most dilute acids with liberation of
hydrogen; the reaction between sulphuric acid and iron turnings being
used for the commercial manufacture of this gas. It dissolves in dilute
cold nitric acid with the formation of ferrous and ammonium nitrates, no
gases being liberated; when heated or with stronger acid ferric nitrate
is formed with evolution of nitrogen oxides.
It was observed by James Keir (_Phil. Trans._, 1790, p. 359) that iron,
after having been immersed in strong nitric acid, is insoluble in acids,
neither does it precipitate metals from solutions. This "passivity" may
be brought about by immersion in other solutions, especially by those
containing such oxidizing anions as NO'3, ClO'3, less strongly by the
anions SO"4 CN', CNS', C2H3O'2, OH', while Cl', Br' practically inhibit
passivity; H' is the only cation which has any effect, and this tends to
exclude passivity. It is also occasioned by anodic polarization of iron
in sulphuric acid. Other metals may be rendered passive; for example,
zinc does not precipitate copper from solutions of the double cyanides
and sulphocyanides, nickel and cadmium from the nitrates, and iron from
the sulphate, but it immediately throws down nickel and cadmium from the
sulphates and chlorides, and lead and copper from the nitrates (see O.
Sackur, _Zeit. Elektrochem._, 1904, 10, p. 841). Anodic polarization in
potassium chloride solution renders molybdenum, niobium, ruthenium,
tungsten, and vanadium passive (W. Muthmann and F. Frauenberger, _Sitz.
Bayer. Akad. Wiss._, 1904, 34, p. 201), and also gold in commercial
potassium cyanide solution (A. Coehn and C. L. Jacobsen, _Abs. J.C.S._,
1907, ii. p. 926). Several hypotheses have been promoted to explain this
behaviour, and, although the question is not definitely settled, the
more probable view is that it is caused by the formation of a film of an
oxide, a suggestion made many years ago by Faraday (see P. Krassa,
_Zeit. Elektrochem._, 1909, 15, p. 490). Fredenhagen (_Zeit. physik.
Chem._, 1903, 43, p. 1), on the other hand, regarded it as due to
surface films of a gas; submitting that the difference between iron made
passive by nitric acid and by anodic polarization was explained by the
film being of nitrogen oxides in the first case and of oxygen in the
second case. H. L. Heathcote and others regard the passivity as
invariably due to electrolytic action (see papers in the _Zeit. physik.
Chem._, 1901 et seq.).
_Compounds of Iron._
_Oxides and Hydroxides._--Iron forms three oxides: ferrous oxide, FeO,
ferric oxide, Fe2O3, and ferroso-ferric oxide, Fe3O4. The first two give
origin to well-defined series of salts, the ferrous salts, wherein the
metal is divalent, and the ferric salts, wherein the metal is trivalent;
the former readily pass into the latter on oxidation, and the latter
into the former on reduction.
_Ferrous oxide_ is obtained when ferric oxide is reduced in hydrogen at
300 deg. as a black pyrophoric powder. Sabatier and Senderens (_Compt.
rend._, 1892, 114, p. 1429) obtained it by acting with nitrous oxide on
metallic iron at 200 deg., and Tissandier by heating the metal to 900
deg. in carbon dioxide; Donau (_Monats._, 1904, 25, p. 181), on the
other hand, obtained a magnetic and crystalline-ferroso-ferric oxide at
1200 deg. It may also be prepared as a black velvety powder which
readily takes up oxygen from the air by adding ferrous oxalate to
boiling caustic potash. Ferrous hydrate, Fe(OH)2, when prepared from a
pure ferrous salt and caustic soda or potash free from air, is a white
powder which may be preserved in an atmosphere of hydrogen. Usually,
however, it forms a greenish mass, owing to partial oxidation. It
oxidizes on exposure with considerable evolution of heat; it rapidly
absorbs carbon dioxide; and readily dissolves in acids to form ferrous
salts, which are usually white when anhydrous, but greenish when
hydrated.
_Ferric oxide_ or iron sesquioxide, Fe2O3, constitutes the valuable ores
red haematite and specular iron; the minerals brown haematite or
limonite, and gothite and also iron rust are hydrated forms. It is
obtained as a steel-grey crystalline powder by igniting the oxide or any
ferric salt containing a volatile acid. Small crystals are formed by
passing ferric chloride vapour over heated lime. When finely ground
these crystals yield a brownish red powder which dissolves slowly in
acids, the most effective solvent being a boiling mixture of 8 parts of
sulphuric acid and 3 of water. Ferric oxide is employed as a pigment, as
jeweller's rouge, and for polishing metals. It forms several hydrates,
the medicinal value of which was recognized in very remote times. Two
series of synthetic hydrates were recognized by Muck and Tommasi: the
"red" hydrates, obtained by precipitating ferric salts with alkalis, and
the "yellow" hydrates, obtained by oxidizing moist ferrous hydroxide or
carbonates. J. van Bemmelen has shown that the red hydrates are really
colloids, the amount of water retained being such that its vapour
pressure equals the pressure of the aqueous vapour in the superincumbent
atmosphere. By heating freshly prepared red ferric hydrate with water
under 5000 atmospheres pressure Ruff (_Ber._, 1901, 34, p. 3417)
obtained definite hydrates corresponding to the minerals limonite (30
deg.-42.5 deg.), gothite (42.5 deg.-62.5 deg.), and hydrohaematite
(above 62.5 deg.). Thomas Graham obtained a soluble hydrate by
dissolving the freshly prepared hydrate in ferric chloride and dialysing
the solution, the soluble hydrate being left in the dialyser. All the
chlorine, however, does not appear to be removed by this process, the
residue having the composition 82Fe(OH)3.FeCl3; but it may be by
electrolysing in a porous cell (Tribot and Chretien, _Compt. rend._,
1905, 140, p. 144). On standing, the solution usually gelatinizes, a
process accelerated by the addition of an electrolyte. It is employed in
medicine under the name _Liquor ferri dialysati_. The so-called soluble
meta-ferric hydroxide, FeO(OH)(?), discovered by Pean de St Gilles in
1856, may be obtained by several methods. By heating solutions of
certain iron salts for some time and then adding a little sulphuric acid
it is precipitated as a brown powder. Black scales, which dissolve in
water to form a red solution, are obtained by adding a trace of
hydrochloric acid to a solution of basic ferric nitrate which has been
heated to 100 deg. for three days. A similar compound, which, however,
dissolves in water to form an orange solution, results by adding salt to
a heated solution of ferric chloride. These compounds are insoluble in
concentrated, but dissolve readily in dilute acids.
Red ferric hydroxide dissolves in acids to form a well-defined series of
salts, the ferric salts, also obtained by oxidizing ferrous salts; they
are usually colourless when anhydrous, but yellow or brown when
hydrated. It has also feebly acidic properties, forming _ferrites_ with
strong bases.
_Magnetite_, Fe3O4, may be regarded as ferrous ferrite, FeO.Fe2O3. This
important ore of iron is most celebrated for its magnetic properties
(see MAGNETISM and COMPASS), but the mineral is not always magnetic,
although invariably attracted by a magnet. It may be obtained
artificially by passing steam over red-hot iron. It dissolves in acids
to form a mixture of a ferrous and ferric salt,[1] and if an alkali is
added to the solution a black precipitate is obtained which dries to a
dark brown mass of the composition Fe(OH)2.Fe2O3; this substance is
attracted by a magnet, and thus may be separated from the admixed ferric
oxide. Calcium ferrite, magnesium ferrite and zinc ferrite, RO.Fe2O3 (R
= Ca, Mg, Zn), are obtained by intensely heating mixtures of the oxides;
magnesium ferrite occurs in nature as the mineral magnoferrite, and zinc
ferrite as franklinite, both forming black octahedra.
_Ferric acid_, H2FeO4. By fusing iron with saltpetre and extracting the
melt with water, or by adding a solution of ferric nitrate in nitric
acid to strong potash, an amethyst or purple-red solution is obtained
which contains potassium ferrate. E. Fremy investigated this discovery,
made by Stahl in 1702, and showed that the same solution resulted when
chlorine is passed into strong potash solution containing ferric hydrate
in suspension. Haber and Pick (_Zeit. Elektrochem._, 1900, 7, p. 215)
have prepared potassium ferrate by electrolysing concentrated potash
solution, using an iron anode. A temperature of 70 deg., and a reversal
of the current (of low density) between two cast iron electrodes every
few minutes, are the best working conditions. When concentrated the
solution is nearly black, and on heating it yields a yellow solution of
potassium ferrite, oxygen being evolved. Barium ferrate, BaFeO4.H2O,
obtained as a dark red powder by adding barium chloride to a solution of
potassium ferrate, is fairly stable. It dissolves in acetic acid to form
a red solution, is not decomposed by cold sulphuric acid, but with
hydrochloric or nitric acid it yields barium and ferric salts, with
evolution of chlorine or oxygen (Baschieri, _Gazetta_, 1906, 36, ii. p.
282).
_Halogen Compounds._--Ferrous fluoride, FeF2, is obtained as
colourless prisms (with 8H2O) by dissolving iron in hydrofluoric acid,
or as anhydrous colourless rhombic prisms by heating iron or ferric
chloride in dry hydrofluoric acid gas. Ferric fluoride, FeF3, is
obtained as colourless crystals (with 4(1/2)H2O) by evaporating a
solution of the hydroxide in hydrofluoric acid. When heated in air it
yields ferric oxide. Ferrous chloride, FeCl2, is obtained as shining
scales by passing chlorine, or, better, hydrochloric acid gas, over
red-hot iron, or by reducing ferric chloride in a current of hydrogen.
It is very deliquescent, and freely dissolves in water and alcohol.
Heated in air it yields a mixture of ferric oxide and chloride, and in
steam magnetic oxide, hydrochloric acid, and hydrogen. It absorbs
ammonia gas, forming the compound FeCl2.6NH2, which on heating loses
ammonia, and, finally, yields ammonium chloride, nitrogen and iron
nitride. It fuses at a red-heat, and volatilizes at a yellow-heat; its
vapour density at 1300 deg.-1400 deg. corresponds to the formula
FeCl2. By evaporating in vacuo the solution obtained by dissolving
iron in hydrochloric acid, there results bluish, monoclinic crystals
of FeCl2.4H2O, which deliquesce, turning greenish, on exposure to air,
and effloresce in a desiccator. Other hydrates are known. By adding
ammonium chloride to the solution, evaporating in vacuo, and then
volatilizing the ammonium chloride, anhydrous ferrous chloride is
obtained. The solution, in common with those of most ferrous salts,
absorbs nitric oxide with the formation of a brownish solution.
Ferric chloride, FeCl3, known in its aqueous solution to Glauber as
_oleum martis_, may be obtained anhydrous by the action of dry
chlorine on the metal at a moderate red-heat, or by passing
hydrochloric acid gas over heated ferric oxide. It forms iron-black
plates or tablets which appear red by transmitted and a metallic green
by reflected light. It is very deliquescent, and readily dissolves in
water, forming a brown or yellow solution, from which several hydrates
may be separated (see SOLUTION). The solution is best prepared by
dissolving the hydrate in hydrochloric acid and removing the excess of
acid by evaporation, or by passing chlorine into the solution obtained
by dissolving the metal in hydrochloric acid and removing the excess
of chlorine by a current of carbon dioxide. It also dissolves in
alcohol and ether; boiling point determinations of the molecular
weight in these solutions point to the formula FeCl3. Vapour density
determinations at 448 deg. indicate a partial dissociation of the
double molecule Fe2Cl6; on stronger heating it splits into ferrous
chloride and chlorine. It forms red crystalline double salts with the
chlorides of the metals of the alkalis and of the magnesium group. An
aqueous solution of ferric chloride is used in pharmacy under the name
_Liquor ferri perchloridi_; and an alcoholic solution constitutes the
quack medicine known as "Lamotte's golden drops." Many oxychlorides
are known; soluble forms are obtained by dissolving precipitated
ferric hydrate in ferric chloride, whilst insoluble compounds result
when ferrous chloride is oxidized in air, or by boiling for some time
aqueous solutions of ferric chloride.
Ferrous bromide, FeBr2, is obtained as yellowish crystals by the union
of bromine and iron at a dull red-heat, or as bluish-green rhombic
tables of the composition FeBr2.6H2O by crystallizing a solution of
iron in hydrobromic acid. Ferric bromide, FeBr3, is obtained as dark
red crystals by heating iron in an excess of bromine vapour. It
closely resembles the chloride in being deliquescent, dissolving
ferric hydrate, and in yielding basic salts. Ferrous iodide, FeI2, is
obtained as a grey crystalline mass by the direct union of its
components. Ferric iodide does not appear to exist.
_Sulphur Compounds._--Ferrous sulphide, FeS, results from the direct
union of its elements, best by stirring molten sulphur with a
white-hot iron rod, when the sulphide drops to the bottom of the
crucible. It then forms a yellowish crystalline mass, which readily
dissolves in acids with the liberation of sulphuretted hydrogen.
Heated in air it at first partially oxidizes to ferrous sulphate, and
at higher temperatures it yields sulphur dioxide and ferric oxide. It
is unaltered by ignition in hydrogen. An amorphous form results when a
mixture of iron filings and sulphur are triturated with water. This
modification is rapidly oxidized by the air with such an elevation of
temperature that the mass may become incandescent. Another black
amorphous form results when ferrous salts are precipitated by ammonium
sulphide.
Ferric sulphide, Fe2S3, is obtained by gently heating a mixture of its
constituent elements, or by the action of sulphuretted hydrogen on
ferric oxide at temperatures below 100 deg. It is also prepared by
precipitating a ferric salt with ammonium sulphide; unless the alkali
be in excess a mixture of ferrous sulphide and sulphur is obtained. It
combines with other sulphides to form compounds of the type M'2Fe2S4.
Potassium ferric sulphide, K2Fe2S4, obtained by heating a mixture of
iron filings, sulphur and potassium carbonate, forms purple glistening
crystals, which burn when heated in air. Magnetic pyrites or
pyrrhotite has a composition varying between Fe7S8 and Fe8S9, i.e.
5FeS.Fe2S3 and 6FeS.Fe2S3. It has a somewhat brassy colour, and occurs
massive or as hexagonal plates; it is attracted by a magnet and is
sometimes itself magnetic. The mineral is abundant in Canada, where
the presence of about 5% of nickel makes it a valuable ore of this
metal. Iron disulphide, FeS2, constitutes the minerals pyrite and
marcasite (q.v.); copper pyrites is (Cu, Fe)S2. Pyrite may be prepared
artificially by gently heating ferrous sulphide with sulphur, or as
brassy octahedra and cubes by slowly heating an intimate mixture of
ferric oxide, sulphur and sal-ammoniac. It is insoluble in dilute
acids, but dissolves in nitric acid with separation of sulphur.
Ferrous sulphite, FeSO3. Iron dissolves in a solution of sulphur
dioxide in the absence of air to form ferrous sulphite and
thio-sulphate; the former, being less soluble than the latter,
separates out as colourless or greenish crystals on standing.
Ferrous sulphate, green vitriol or copperas, FeSO4.7H2O, was known to,
and used by, the alchemists; it is mentioned in the writings of
Agricola, and its preparation from iron and sulphuric acid occurs in
the _Tractatus chymico-philosophicus_ ascribed to Basil Valentine. It
occurs in nature as the mineral melanterite, either crystalline or
fibrous, but usually massive; it appears to have been formed by the
oxidation of pyrite or marcasite. It is manufactured by piling pyrites
in heaps and exposing to atmospheric oxidation, the ferrous sulphate
thus formed being dissolved in water, and the solution run into tanks,
where any sulphuric acid which may be formed is decomposed by adding
scrap iron. By evaporation the green vitriol is obtained as large
crystals. The chief impurities are copper and ferric sulphates; the
former may be removed by adding scrap iron, which precipitates the
copper; the latter is eliminated by recrystallization. Other
impurities such as zinc and manganese sulphates are more difficult to
remove, and hence to prepare the pure salt it is best to dissolve pure
iron wire in dilute sulphuric acid. Ferrous sulphate forms large green
crystals belonging to the monoclinic system; rhombic crystals,
isomorphous with zinc sulphate, are obtained by inoculating a solution
with a crystal of zinc sulphate, and triclinic crystals of the formula
FeSO4.5H2O by inoculating with copper sulphate. By evaporating a
solution containing free sulphuric acid in a vacuum, the
hepta-hydrated salt first separates, then the penta-, and then a
tetra-hydrate, FeSO4.4H2O, isomorphous with manganese sulphate. By
gently heating in a vacuum to 140 deg., the hepta-hydrate loses 6
molecules of water, and yields a white powder, which on heating in the
absence of air gives the anhydrous salt. The monohydrate also results
as a white precipitate when concentrated sulphuric acid is added to a
saturated solution of ferrous sulphate. Alcohol also throws down the
salt from aqueous solution, the composition of the precipitate varying
with the amount of salt and precipitant employed. The solution absorbs
nitric oxide to form a dark brown solution, which loses the gas on
heating or by placing in a vacuum. Ferrous sulphate forms double salts
with the alkaline sulphates. The most important is ferrous ammonium
sulphate, FeSO4.(NH4)2SO4.6H2O, obtained by dissolving equivalent
amounts of the two salts in water and crystallizing. It is very
stable and is much used in volumetric analysis.
Ferric sulphate, Fe2(SO4)3, is obtained by adding nitric acid to a hot
solution of ferrous sulphate containing sulphuric acid, colourless
crystals being deposited on evaporating the solution. The anhydrous
salt is obtained by heating, or by adding concentrated sulphuric acid
to a solution. It is sparingly soluble in water, and on heating it
yields ferric oxide and sulphur dioxide. The mineral coquimbite is
Fe2(SO4)3.9H2O. Many basic ferric sulphates are known, some of which
occur as minerals; carphosiderite is Fe(FeO)5(SO4)4.10H2O; amarantite
is Fe(FeO)(SO4)2.7H2O; utahite is 3(FeO)2SO4.4H2O; copiapite is
Fe3(FeO)(SO4)5.18H2O; castanite is Fe(FeO)(SO4)2.8H2O; romerite is
FeSO4.Fe2(SO4)3.12H2O. The iron alums are obtained by crystallizing
solutions of equivalent quantities of ferric and an alkaline sulphate.
Ferric potassium sulphate, the common iron alum,
K2SO4.Fe2(SO4)3.24H2O, forms bright violet octahedra.
_Nitrides, Nitrates, &c._--Several nitrides are known. Guntz (_Compt.
rend._, 1902, 135, p. 738) obtained ferrous nitride, Fe3N2, and ferric
nitride, FeN, as black powders by heating lithium nitride with ferrous
potassium chloride and ferric potassium chloride respectively. Fowler
(_Jour. Chem. Soc._, 1901, p. 285) obtained a nitride Fe2N by acting
upon anhydrous ferrous chloride or bromide, finely divided reduced
iron, or iron amalgam with ammonia at 420 deg.; and, also, in a compact
form, by the action of ammonia on red-hot iron wire. It oxidizes on
heating in air, and ignites in chlorine; on solution in mineral acids
it yields ferrous and ammonium salts, hydrogen being liberated. A
nitride appears to be formed when nitrogen is passed over heated iron,
since the metal is rendered brittle. Ferrous nitrate, Fe(NO3)2.6H2O,
is a very unstable salt, and is obtained by mixing solutions of
ferrous sulphate and barium nitrate, filtering, and crystallizing in a
vacuum over sulphuric acid. Ferric nitrate, Fe(NO3)3, is obtained by
dissolving iron in nitric acid (the cold dilute acid leads to the
formation of ferrous and ammonium nitrates) and crystallizing, when
cubes of Fe(NO3)3.6H2O or monoclinic crystals of Fe(NO3)3.9H2O are
obtained. It is used as a mordant.
Ferrous solutions absorb nitric oxide, forming dark green to black
solutions. The coloration is due to the production of unstable
compounds of the ferrous salt and nitric oxide, and it seems that in
neutral solutions the compound is made up of one molecule of salt to
one of gas; the reaction, however, is reversible, the composition
varying with temperature, concentration and nature of the salt.
Ferrous chloride dissolved in strong hydrochloric acid absorbs two
molecules of the gas (Kohlschutter and Kutscheroff, _Ber._, 1907, 40,
p. 873). Ferric chloride also absorbs the gas. Reddish brown amorphous
powders of the formulae 2FeCl3.NO and 4FeCl3.NO are obtained by
passing the gas over anhydrous ferric chloride. By passing the gas
into an ethereal solution of the salt, nitrosyl chloride is produced,
and on evaporating over sulphuric acid, black needles of FeCl2.NO.2H2O
are obtained, which at 60 deg. form the yellow FeCl2.NO. Complicated
compounds, discovered by Roussin in 1858, are obtained by the
interaction of ferrous sulphate and alkaline nitrites and sulphides.
Two classes may be distinguished:--(1) the ferrodinitroso salts, e.g.
K[Fe(NO)2S], potassium ferrodinitrososulphide, and (2) the
ferroheptanitroso salts, e.g. K[Fe4(NO)7S8], potassium
ferroheptanitrososulphide. These salts yield the corresponding acids
with sulphuric acid. The dinitroso acid slowly decomposes into
sulphuretted hydrogen, nitrogen, nitrous oxide, and the heptanitroso
acid. The heptanitroso acid is precipitated as a brown amorphous mass
by dilute sulphuric acid, but if the salt be heated with strong acid
it yields nitrogen, nitric oxide, sulphur, sulphuretted hydrogen, and
ferric, ammonium and potassium sulphates.
_Phosphides, Phosphates._--H. Le Chatelier and S. Wologdine (_Compt.
rend._, 1909, 149, p. 709) have obtained Fe3P, Fe2P, FeP, Fe2P3, but
failed to prepare five other phosphides previously described. Fe3P
occurs as crystals in the product of fusing iron with phosphorus; it
dissolves in strong hydrochloric acid. Fe2P forms crystalline needles
insoluble in acids except aqua regia; it is obtained by fusing copper
phosphide with iron. FeP is obtained by passing phosphorus vapour over
Fe2P at a red-heat. Fe2P3 is prepared by the action of phosphorus
iodide vapour on reduced iron. Ferrous phosphate, Fe3(PO4)2.8H2O,
occurs in nature as the mineral vivianite. It may be obtained
artificially as a white precipitate, which rapidly turns blue or green
on exposure, by mixing solutions of ferrous sulphate and sodium
phosphate. It is employed in medicine. Normal ferric phosphate,
FePO4.2H2O, occurs as the mineral strengite, and is obtained as a
yellowish-white precipitate by mixing solutions of ferric chloride and
sodium phosphate. It is insoluble in dilute acetic acid, but dissolves
in mineral acids. The acid salts Fe(H2PO4)3 and 2FeH3(PO4)2.5H2O have
been described. Basic salts have been prepared, and several occur in
the mineral kingdom; dufrenite is Fe2(OH)3PO4.
_Arsenides, Arsenites, &c._--Several iron arsenides occur as minerals;
lolingite, FeAs2, forms silvery rhombic prisms; mispickel or arsenical
pyrites, Fe2AsS2, is an important commercial source of arsenic. A
basic ferric arsenite, 4Fe2O3.As2O3.5H2O, is obtained as a flocculent
brown precipitate by adding an arsenite to ferric acetate, or by
shaking freshly prepared ferric hydrate with a solution of arsenious
oxide. The last reaction is the basis of the application of ferric
hydrate as an antidote in arsenical poisoning. Normal ferric
arsenate, FeAsO4.2H2O, constitutes the mineral scorodite;
pharmacosiderite is the basic arsenate 2FeAsO4.Fe(OK)3.5H2O. An acid
arsenate, 2Fe2(HAsO4)3.9H2O, is obtained as a white precipitate by
mixing solutions of ferric chloride and ordinary sodium phosphate. It
readily dissolves in hydrochloric acid.
_Carbides, Carbonates._--The carbides of iron play an important part
in determining the properties of the different modifications of the
commercial metal, and are discussed under IRON AND STEEL.
Ferrous carbonate, FeCO3, or spathic iron ore, may be obtained as
microscopic rhombohedra by adding sodium bicarbonate to ferrous
sulphate and heating to 150 deg. for 36 hours. Ferrous sulphate and
sodium carbonate in the cold give a flocculent precipitate, at first
white but rapidly turning green owing to oxidation. A soluble
carbonate and a ferric salt give a precipitate which loses carbon
dioxide on drying. Of great interest are the carbonyl compounds.
Ferropentacarbonyl, Fe(CO)5, obtained by L. Mond, Quincke and Langer
(_Jour. Chem. Soc._, 1891; see also ibid. 1910, p. 798) by treating
iron from ferrous oxalate with carbon monoxide, and heating at 150
deg., is a pale yellow liquid which freezes at about -20 deg., and
boils at 102.5 deg. Air and moisture decompose it. The halogens give
ferrous and ferric haloids and carbon monoxide; hydrochloric and
hydrobromic acids have no action, but hydriodic decomposes it. By
exposure to sunlight, either alone or dissolved in ether or ligroin,
it gives lustrous orange plates of diferrononacarbonyl, Fe2(CO)9. If
this substance be heated in ethereal solution to 50 deg., it deposits
lustrous dark-green tablets of ferrotetracarbonyl, Fe(CO)4, very
stable at ordinary temperatures, but decomposing at 140 deg.-150 deg.
into iron and carbon monoxide (J. Dewar and H. O. Jones, _Abst.
J.C.S._, 1907, ii. 266). For the cyanides see PRUSSIC ACID.
Ferrous salts give a greenish precipitate with an alkali, whilst
ferric give a characteristic red one. Ferrous salts also give a bluish
white precipitate with ferrocyanide, which on exposure turns to a dark
blue; ferric salts are characterized by the intense purple coloration
with a thiocyanate. (See also CHEMISTRY, S _Analytical_). For the
quantitative estimation see ASSAYING.
A recent atomic weight determination by Richards and Baxter (_Zeit.
anorg. Chem._, 1900, 23, p. 245; 1904, 38, p. 232), who found the
amount of silver bromide given by ferrous bromide, gave the value
55.44 [O = 16].
_Pharmacology._
All the official salts and preparations of iron are made directly or
indirectly from the metal. The pharmacopoeial forms of iron are as
follow:--
1. _Ferrum_, annealed iron wire No. 35 or wrought iron nails free from
oxide; from which we have the preparation _Vinum ferri_, iron wine,
iron digested in sherry wine for thirty days. (Strength, 1 in 20.)
2. _Ferrum redactum_, reduced iron, a powder containing at least 75%
of metallic iron and a variable amount of oxide. A preparation of it
is _Trochiscus ferri redacti_ (strength, 1 grain of reduced iron in
each).
3. _Ferri sulphas_, ferrous sulphate, from which is prepared _Mistura
ferri composita_, "Griffiths' mixture," containing ferrous sulphate 25
gr., potassium carbonate 30 gr., myrrh 60 gr., sugar 60 gr., spirit of
nutmeg 50 m., rose water 10 fl. oz.
4. _Ferri sulphas exsiccatus_, which has two subpreparations: (a)
_Pilula ferri_, "Blaud's pill" (exsiccated ferrous sulphate 150,
exsiccated sodium carbonate 95, gum acacia 50, tragacanth 15, glycerin
10, syrup 150, water 20, each to contain about 1 grain of ferrous
carbonate); (b) _Pilula aloes et ferri_ (Barbadoes aloes 2, exsiccated
ferrous sulphate 1, compound powder of cinnamon 3, syrup of glucose
3).
5. _Ferri carbonas saccharatus_, saccharated iron carbonate. The
carbonate forms about one-third and is mixed with sugar into a greyish
powder.
6. _Ferri arsenas_, iron arsenate, ferrous and ferric arsenates with
some iron oxides, a greenish powder.
7. _Ferri phosphas_, a slate-blue powder of ferrous and ferric
phosphates with some oxide. Its preparations are: (a) _Syrupus ferri
phosphatis_ (strength, 1 gr. of ferrous phosphate in each fluid
drachm); (b) _Syrupus ferri phosphatis cum quinina et strychnina_,
"Easton's syrup" (iron wire 75 grs., concentrated phosphoric acid 10
fl. dr., powdered strychnine 5 gr., quinine sulphate 130 gr., syrup 14
fl. oz., water to make 20 fl. oz.), in which each fluid drachm
represents 1 gr. of ferrous phosphate, 4/5 gr. of quinine sulphate,
and 1/32 gr. of strychnine.
8. _Syrupus ferri iodidi_, iron wire, iodine, water and syrup
(strength, 5.5 gr. of ferrous iodide in one fl. dr.).
9. _Liquor ferri perchloridi fortis_, strong solution of ferric
chloride (strength, 22.5% of iron); its preparations only are
prescribed, viz. _Liquor ferri perchloridi_ and _Tinctura ferri
perchloridi_.