See J. Cameron Lees,History of the County of Inverness(Edinburgh, 1897); C. Fraser-Mackintosh,Letters of Two Centuries(Inverness, 1890); Alexander Mackenzie,Histories of the Mackenzies, Camerons, &c. (Inverness, 1874-1896); A. Stewart,Nether Lochaber(Edinburgh, 1883); Alexander Carmichael, “Grazing and Agrestic Customs of the Outer Hebrides” (Crofters’ Commission Report, 1884).
See J. Cameron Lees,History of the County of Inverness(Edinburgh, 1897); C. Fraser-Mackintosh,Letters of Two Centuries(Inverness, 1890); Alexander Mackenzie,Histories of the Mackenzies, Camerons, &c. (Inverness, 1874-1896); A. Stewart,Nether Lochaber(Edinburgh, 1883); Alexander Carmichael, “Grazing and Agrestic Customs of the Outer Hebrides” (Crofters’ Commission Report, 1884).
INVERSION(Lat.invertere, to turn about), in chemistry, the name given to the hydrolysis of cane sugar into a mixture of glucose and fructose (invert sugar); it was chosen because the operation was attended by a change from dextro-rotation of polarized light to a laevo-rotation. In mathematics, inversion is a geometrical method, discovered jointly by Stubbs and Ingram of Dublin, and employed subsequently with conspicuous success by Lord Kelvin in his electrical researches. The notion may be explained thus: If R be a circle of centre O and radiusr, and P, Q be two points on a radius such that OP·OQ =r2, then P, Q are said to be inverse points for a circle of radiusr, and O is the centre of inversion. If one point, say P, traces a curve, the corresponding locus of Q is said to be the inverse of the path of P. The fundamental propositions are: (1) the inverse of a circle is a line or a circle according as the centre of inversion is on or off the circumference; (2) the angle at theintersection of two circles or of a line and a circle is unaltered by inversion. The method obviously affords a ready means for converting theorems involving lines and circles into other propositions involving the same, but differently placed, figures; in mathematical physics it is of special value in solving geometrically electrostatical and optical problems.
INVERURIE,a royal, municipal and police burgh of Aberdeenshire, Scotland, situated at the confluence of the rivers Don and Ury, 16¼ m. N.W. of Aberdeen by rail, on the Great North of Scotland railway. Pop. (1901) 3624. Paper-making, milling, and the making of mineral waters are the chief manufactures, but the town is an important centre of the cattle trade with London, markets being held at frequent intervals. It also contains the workshops of the Great North of Scotland railway. Inverurie belongs to the Elgin district group of parliamentary burghs. At Harlaw, about 3 m. to the N.W., was fought in 1411 the great battle between Donald, lord of the Isles, and the royal forces under the earl of Mar. Not far from the scene of this conflict stands Balquhain Castle, a seat of the Leslies, now a mere shell, which was occupied by Queen Mary in September 1562 before the fight at Corrichie between her forces, led by the earl of Moray, and those of the earl of Huntly. The granite block from which she is said to have viewed the combat is still called the Queen’s Chair or the Maiden Stone. Near Bennachie (1619 ft.) are stone circles and monoliths supposed to be of Druidical origin. There is a branch line from Inverurie to Old Meldrum, 5¾ m. to the N.E. by rail, a market town with a charter dating from 1672, where brewing and distilling are carried on.
INVESTITURE(Late Lat.investitura), the formal installation into an office or estate, which constituted in the middle ages one of the acts that betokened the feudal relation between suzerain and vassal. The suzerain, after receiving the vassal’s homage and oath of fealty, invested him with his land or office by presenting some symbol, such as a clod, a banner, a branch, or some other object according to the custom of the fief. Otto of Freising says: “It is customary when a kingdom is delivered over to any one that a sword be given to represent it, and when a province is transferred a standard is given.” As feudal customs grew more stereotyped, the sword and sceptre, emblematic respectively of service and military command and of judicial prerogatives, became the usual emblems of investiture of laymen. The word investiture (fromvestire, to put in possession) is later than the 9th century; the thing itself was an outcome of feudal society.
It is in connexion with the Church that investiture has its greatest historical interest. The Church quite naturally shared in feudal land-holding; in addition to the tithes she possessed immense estates which had been given her by the faithful from early times, and for the defence of which she resorted to secular means. The bishops and abbots, by confiding their domains to laymen on condition of assistance with the sword in case of need, became temporal lords and suzerains with vassals to fight for them, with courts of justice, and in short with all the rights and privileges exercised by lay lords. On the other hand there were bishop-dukes, bishop-counts, &c., themselves vassals of other lords, and especially of the king, from whom they received the investiture of their temporalities. Many of the faithful founded abbeys and churches on condition that the right of patronage, that is the choice of beneficiaries, should be reserved to them and their heirs. Thus in various ways ecclesiastical benefices were gradually transformed into fiefs, and lay suzerains claimed the same rights over ecclesiastics as over other vassals from whom they received homage, and whom they invested with lands. This ecclesiastical investiture by lay princes dates at least from the time of Charlemagne. It did not seem fitting at first to confer ecclesiastical investiture by such military and worldly emblems as the sword and sceptre, nor to exact an oath of fealty. The emperor Henry I. invested bishops with a glove; Otto II. presented the pastoral staff; Conrad II., according to Wipo, went farther and required from the archbishop of Milan an oath of fealty. By the time of Henry III. investiture with ring and crozier had become the general practice: it probably had been customary in some places since Otto II.
Investiture of ecclesiastics by laymen had certain serious effects which were bound to bring on a conflict between the temporal and spiritual authorities. In the first place the lay authorities often rendered elections uncanonical by interfering in behalf of some favourite, thereby impairing the freedom of the electors. Again, benefices were kept vacant for long periods in order to ensure to the lord as long as possible the exercise of his regalian rights. And, finally, control by temporal princes of investiture, and indirectly of election, greatly increased simony. Otto II. is charged with having practised simony in this connexion, and under Conrad II. the abuse grew prevalent. At a synod at Reims in 1049, the bishops of Nevers and Coutances affirmed that they had bought their bishoprics, and the bishop of Nantes stated that his father had been a bishop and that on his decease he himself had purchased the see. At a synod at Toulouse in 1056, Berengar of Narbonne accused the bishop of having purchased his see for 100,000solidi, and of having plundered his church and sold relics and crucifixes to Spanish Jews in order to secure another 100,000solidiwith which to buy for his brother the bishopric of Urgel. Innumerable similar cases appear in acts of synods and in chronicles during the 11th century. Ecclesiastical investiture was further complicated by the considerable practice of concubinage. There was always the tendency for clerics in such cases to invest their sons with the temporalities of the Church; and the synod convened by Benedict VIII. at Pavia in 1018 (or 1022 according to some authorities) was mainly concerned with the issue of decrees against clerics who lived with wives or concubines and bestowed Church goods on their children. In time the Church came to perceive how closely lay investiture was bound up with simony. The sixth decree of the Lateran synod of 1059 forbade any cleric to accept Church office from a layman. In the following year this decree was reaffirmed by synods held at Vienne and Toulouse under the presidency of a legate of Nicholas II. The main investiture struggle with the empire did not take place, however, until Hildebrand became Pope Gregory VII. To Gregory it was intolerable that a layman, whether emperor, king or baron, should invest a churchman with the emblems of spiritual office; ecclesiastical investiture should come only from ecclesiastics. To the emperor Henry IV. it was highly undesirable that the advantages and revenues accruing from lay investiture should be surrendered; it was reasonable that ecclesiastics should receive investiture of temporalities from their temporal protectors and suzerains.
Although the full text of the decrees of the famous Lenten synod of 1075 has not been preserved, it is known that Gregory on that occasion denounced the marriage of the clergy, excommunicated five of Henry IV.’s councillors on the ground that they had gained church offices through simony, and forbade the emperor and all laymen to grant investiture of bishopric or inferior dignity. The pope immediately summoned Henry to appear at Rome in order to justify his private misconduct, and Henry replied by causing the partisan synod of Worms (1076) to pronounce Gregory’s deposition. The pope excommunicated the emperor and stirred up civil war against him in Saxony with such success that he brought about Henry’s bitter humiliation at Canossa in the following year. The papal prohibition of lay investiture was renewed at synods in 1078 and 1080, and although Gregory’s death in exile (1085) prevented him from realizing his aim in the matter, his policy was steadfastly maintained by his successors. Victor III. condemned lay investiture at the synod of Benevento in 1087, and Urban II. at that of Melfi in 1089. At the celebrated council of Clermont (1095), at which the first crusade was preached, Urban strengthened the former prohibitions by declaring that no one might accept any spiritual office from a layman, or take an oath of fealty to any layman. Urban’s immediate successor, Paschal II., stirred up the rebellion of the emperor’s son, but soon found Henry V. even more persistent in the claim ofinvestiture than Henry IV. had been. Several attempts at settlement failed. In February 1111 legates of Paschal II. met Henry V. at Sutri and declared that the pope was ready to surrender all the temporalities that had been bestowed on the clergy since the days of Charlemagne in return for freedom of election and the abolition of lay investiture. Henry, having agreed to the proposal, entered Rome to receive his crown. The bishops and clergy who were present at the coronation protested against this surrender, and a tumult arising, the ceremony had to be abandoned. The king then seized pope and curia and left the city. After two months of close confinement Paschal consented to an unqualified renunciation on his part of the right of investiture. In the following year, however, a Lateran council repudiated this compact as due to violence, and a synod held at Vienne with papal approval declared lay investiture to be heresy and placed Henry under the ban. The struggle was complicated throughout its course by political and other considerations; there were repeated rebellions of German nobles, constant strife between rival imperial and papal factions in the Lombard cities and at Rome, and creation of several anti-popes, of whom Guibert of Ravenna (Clement III.) and Gregory VIII. were the most important. Final settlement of the struggle was retarded, moreover, by the question of the succession to the lands of the great Countess Matilda, who had bequeathed all her property to the Holy See, Henry claiming the estates as suzerain of the fiefs and as heir of the allodial lands. The efforts of Gelasius II. to settle the strife by a general council were rendered fruitless by his death (1119).
At length in 1122 the struggle was brought to an end by the concordat of Worms, the provisions of which were incorporated in the eighth and ninth canons of the general Lateran council of 1123. The settlement was a compromise. The emperor, on the one hand, preserved feudal suzerainty over ecclesiastical benefices; but, on the other, he ceased to confer ring and crozier, and thereby not only lost the right of refusing the elect on the grounds of unworthiness, but also was deprived of an efficacious means of maintaining vacancies in ecclesiastical offices. Few efforts were made to undo the compromise. King Lothair the Saxon demanded of Innocent II. the renewal of lay investiture as reward for driving the antipope Anacletus from Rome, but the opposition of St Bernard and the German prelates was so potent that the king dropped his demand, and Innocent in 1133 confirmed the concordat. In fact, the imperial control over the election of bishops in Germany came later to be much curtailed in practice, partly by the tacitly changed relations between the empire and its feudatories, partly by explicit concessions wrung at various times from individual emperors, such as Otto IV. in 1209 and Frederick II. in 1213; but the principles of the concordat of Worms continued theoretically to regulate the tenure of bishoprics and abbacies until the dissolution of the empire on 1806.
In France the course of the struggle was somewhat different. As in the empire, the king and the nobles, each within his own sphere of influence, claimed the right of investing with ring and crozier and of exacting homage and oaths of fealty. The struggle, however, was less bitter chiefly because France was not a united country, and it was eventually terminated without formal treaty. The king voluntarily abandoned lay investiture and the claim to homage during the pontificate of Paschal II., but continued to interfere with elections, to appropriate the revenues of vacant benefices, and to exact an oath of fealty before admitting the elect to the enjoyment of his temporalities. Most of the great feudal lords followed the king’s example, but their concessions varied considerably, and in the south of France some of the bishops were still doing homage for their sees until the closing years of the 13th century; but long before then the right of investing with ring and crozier had disappeared from every part of France.
England was the scene of an investiture contest in which the chief actors were Henry I. and Anselm. The archbishop, in obedience to the decrees of Gregory VII. and Urban II., not only refused to perform homage to the king (1100), but also refused to consecrate newly-chosen bishops who had received investiture from Henry. The dispute was bitter, but was carried on without any of the violence which characterized the conflict between papacy and empire; and it ended in a compromise which closely foreshadowed the provisions of the concordat of Worms and received the confirmation of Paschal II. in 1106. Freedom of election, somewhat similar in form to that which still exists, was formally conceded under Stephen, and confirmed by John in Magna Carta.
Many documents relating to the investiture struggle have been edited by E. Dümmler inMonumenta Germaniae historica, Libelli de lite imperatorum et pontificum saeculis xi. et xii.(3 vols., 1891-1897), See Ducange,Glossarium,s.v.“Investitura.”On investiture in the empire consult C. Mirbt,Die Publizistik im Zeitalter Gregors VII.(Leipzig, 1894); E. Bernheim,Das Wormser Konkordat(Breslau, 1906); R. Boerger,Die Belehnungen der deutschen geistlichen Fürsten(Leipzig, 1901); K. E. Benz,Die Stellung der Bischöfe von Meissen, Merseburg und Naumburg im Investiturstreite unter Heinrich IV. und Heinrich V.(Dresden, 1899); W. Martens,Gregor VII., sein Leben und Wirken(2 vols., Leipzig, 1894); P. Fisher,The Medieval Empire, c. 10 (London, 1898). For France, see P. Imbart de la Tour,Les Élections épiscopales dans l’église de France du XIeau XIIesiècle(Paris, 1891); A. Luchaire,Histoire des institutions monarchiques de la France sous les premiers Capétiens 987-1180(2nd ed., Paris, 1891); P. Viollet,Histoire des institutions politiques et administratives de la France(Paris, 1898); Ibach,Der Kampf zwischen Papsttum und Königtum von Gregor VII. bis Calixto II.(Frankfort, 1884). For England, see J. F. Böhmer,Kirche und Staat in England und in der Normandie in XI. und XII. Jahrhundert(Leipzig, 1899); E. A. Freeman,The Reign of William II. Rufus and the Accession of Henry I.(London, 1882); H. W. C. Davis,England under the Normans and Angevins(London, 1905).
Many documents relating to the investiture struggle have been edited by E. Dümmler inMonumenta Germaniae historica, Libelli de lite imperatorum et pontificum saeculis xi. et xii.(3 vols., 1891-1897), See Ducange,Glossarium,s.v.“Investitura.”
On investiture in the empire consult C. Mirbt,Die Publizistik im Zeitalter Gregors VII.(Leipzig, 1894); E. Bernheim,Das Wormser Konkordat(Breslau, 1906); R. Boerger,Die Belehnungen der deutschen geistlichen Fürsten(Leipzig, 1901); K. E. Benz,Die Stellung der Bischöfe von Meissen, Merseburg und Naumburg im Investiturstreite unter Heinrich IV. und Heinrich V.(Dresden, 1899); W. Martens,Gregor VII., sein Leben und Wirken(2 vols., Leipzig, 1894); P. Fisher,The Medieval Empire, c. 10 (London, 1898). For France, see P. Imbart de la Tour,Les Élections épiscopales dans l’église de France du XIeau XIIesiècle(Paris, 1891); A. Luchaire,Histoire des institutions monarchiques de la France sous les premiers Capétiens 987-1180(2nd ed., Paris, 1891); P. Viollet,Histoire des institutions politiques et administratives de la France(Paris, 1898); Ibach,Der Kampf zwischen Papsttum und Königtum von Gregor VII. bis Calixto II.(Frankfort, 1884). For England, see J. F. Böhmer,Kirche und Staat in England und in der Normandie in XI. und XII. Jahrhundert(Leipzig, 1899); E. A. Freeman,The Reign of William II. Rufus and the Accession of Henry I.(London, 1882); H. W. C. Davis,England under the Normans and Angevins(London, 1905).
INVOICE(originally a plural,InvoyesorInvoys, ofInvoy, a variant of “envoy,” from the Frenchenvoyer, to send), a statement giving full particulars of goods sent or shipped by a trader to a customer, with the quantity, quality and prices, and the charges upon them. Consular invoices,i.e.invoices signed at the port of shipment by a consul of the country to which the goods are being consigned, are generally demanded by those countries which imposead valoremduties.
INVOLUTION(Lat.involvere, to roll up), a rolling up or complication. In arithmetic, involution is the operation of raising a quantity to any power; it is the converse of evolution, which is the operation of extracting any root of a quantity (seeArithmetic;Algebra). In geometry, an involution is a one-to-one correspondence between two ranges of points or between two pencils (seeGeometry:Projective). The “involute” of a curve may be regarded as the locus of the extremity of a string when it is unwrapped from the curve (seeInfinitesimal Calculus).
IO,in Greek mythology, daughter of Inachus, the river-god of Argos and its first king. As associated with the oldest worship of Hera she is called the daughter of Peiren, who made the first image of that goddess out of a pear-tree at Tiryns; and under the name of Callithyia Io was regarded as the first priestess of Hera. Zeus fell in love with her, and, to protect her from the wrath of Hera, changed her into a white heifer (Apollodorus ii. 1; Hyginus,Fab.145; Ovid,Metam.i. 568-733); according to Aeschylus (Supplices, 299) the metamorphosis was the work of Hera herself. Hera, having persuaded Zeus to give her the heifer, set Argus Panoptes to watch her. Zeus thereupon sent Hermes, who lulled Argus to sleep and cut off his head with the sword with which Perseus afterwards slew the Gorgon. In another account Argus is killed by a stone thrown by Hermes. But the wrath of Hera still pursued Io. Maddened by a gadfly sent by the goddess she wandered all over the earth, swam the strait known on this account as the Bosporus (Ox-ford), and crossed the Ionian sea (traditionally called after her) until at last she reached Egypt, where she was restored to her original form and became the mother of Epaphus. Accounts of her wanderings (differing considerably in detail) are given in theSupplicesandPrometheus Vinctusof Aeschylus. Various interpretations are given of the latter part of her story, which dates from the 7th centuryB.C., when intercourse was frequent between Greece and Egypt, and when much influence wasexerted on Greek thought by Egyptian religion. According to the rationalistic explanation of Herodotus (i. 1) Io was an Argive princess who was carried off to Egypt by the Phoenicians. Epaphus, the son of Io, the supposed founder of Memphis, was identified with Apis. He was said to have been carried off by order of Hera to Byblus in Syria, where he was found again by Io. On returning to Egypt, Io, afterwards identified with Isis, married Telegonus and founded the royal families of Egypt, Phoenicia, Argos and Thebes. The journey to Syria in search of Epaphus was invented to explain the fact that the Phoenician goddess Astarte, who was sometimes represented as horned, was confounded with Io.
Io herself is variously interpreted. She is usually understood to be the moon in the midst of the mighty heaven, studded with stars, represented by Argus. According to others, she is the annual rising of the Nile; the personification of the Ionian race; the mist; the earth. It seems probable that she was a duplicate of Hera (Ioβούκερωςis Heraβοῶπις), or a deity in primitive times worshipped under the symbol of a cow, whose worship was superseded by that of Hera; the recollection of this early identity would account for Io being regarded as the priestess of the goddess in later times. Amongst the Romans she was sometimes identified with Anna Perenna. The legend of Io spread beyond Argos, especially in Byzantium and Euboea, where it was associated with the town of Argura. It was a favourite subject among Greek painters, and many representations of it are preserved on vases and wall paintings; Io herself appears as a horned maiden or as the heifer watched by Argus.
See R. Engelmann,De Ione(1868), with notes containing references to authorities, and his article in Roscher’sLexikon der Mythologie; J. Overbeck,De Ione, telluris, non lunae, Dea(1872); P. W. Forchhammer,Die Wanderungen der Inachostochter Io(1881), with map and special reference to Aeschylus’s account of Io’s wanderings; F. Durrbach in Daremberg and Saglio’sDictionnaire des antiquités; G. Mellén,De Ius fabula(1901); Wernickes.v.“Argos” in Pauly-Wissowa’sRealencyclopädie, ii. pt. i. (1896); J. E. Harrison inClassical Review(1893, p. 76); Bacchylides xviii. (xix.), with Jebb’s notes.
See R. Engelmann,De Ione(1868), with notes containing references to authorities, and his article in Roscher’sLexikon der Mythologie; J. Overbeck,De Ione, telluris, non lunae, Dea(1872); P. W. Forchhammer,Die Wanderungen der Inachostochter Io(1881), with map and special reference to Aeschylus’s account of Io’s wanderings; F. Durrbach in Daremberg and Saglio’sDictionnaire des antiquités; G. Mellén,De Ius fabula(1901); Wernickes.v.“Argos” in Pauly-Wissowa’sRealencyclopädie, ii. pt. i. (1896); J. E. Harrison inClassical Review(1893, p. 76); Bacchylides xviii. (xix.), with Jebb’s notes.
IODINE(symbol I, atomic weight 126.92), a chemical element, belonging to the halogen group. Its name is derived from Gr.ἰοειδής(violet-coloured), in allusion to the colour of its vapour. It was discovered in 1812 by B. Courtois when investigating the products obtained from the mother-liquors prepared by lixiviating kelp or burnt seaweed, and in 1815 L. J. Gay-Lussac showed that it was an element. Iodine does not occur in nature in the uncombined condition, but is found very widely but sparingly distributed in the form of iodides and iodates, chiefly of sodium and potassium. It is also found in small quantities in sea-water, in some seaweeds, and in various mineral and medicinal springs. Deep-sea weeds as a rule contain more iodine than those which are found in the shallow waters.
Iodine is obtained either from kelp (the ashes of burnt seaweed) or from the mother-liquors obtained in the purification of Chile saltpetre. In the former case the seaweed is burnt in large heaps, care being taken that too high a temperature is not reached, for if the ash be allowed to fuse much iodine is lost by volatilization. The product obtained after burning is known either askelporvarec. Another method of obtaining kelp is to heat the seaweed in large retorts, whereby tarry and ammoniacal liquors pass over and a very porous residue of kelp remains. A later method consists in boiling the weed with sodium carbonate; the liquid is filtered and hydrochloric acid added to the filtrate, whenalginic acidis precipitated; this is also filtered off, the filtrate neutralized by caustic soda, and the whole evaporated to dryness and carbonized, the residue obtained being known askelp substitute. The kelp obtained by any of these methods is then lixiviated with water, which extracts the soluble salts, and the liquid is concentrated, when the less soluble salts, which are chiefly alkaline chlorides, sulphates and carbonates, crystallize out and are removed. Sulphuric acid is now added to the liquid, and any alkaline sulphides and sulphites present are decomposed, while iodides and bromides are converted into sulphates, and hydriodic and hydrobromic acids are liberated and remain dissolved in the solution. The liquid is run into the iodine still and gently warmed, manganese dioxide in small quantities being added from time to time, when the iodine distils over and is collected. In the second method it is found that the mother-liquors obtained from Chile saltpetre contain small quantities of sodium iodate NaIO3; this liquor is mixed with the calculated quantity of sodium bisulphite in large vats, and iodine is precipitated:—
2NaIO3+ 5NaHSO3= 3NaHSO4+ 2Na2SO4+ H2O + I2.
The precipitate is washed and then distilled from iron retorts. Iodine may also be prepared by the decomposition of an iodide with chlorine, or by heating a mixture of an iodide and manganese dioxide with concentrated sulphuric acid. Commercial iodine may be purified by mixing it with a little potassium iodide and then subliming the mixture; in this way any traces of bromine or chlorine are removed. J. S. Stas recommends solution of the iodine in potassium iodide and subsequent precipitation by the addition of a large excess of water, the precipitate being washed, distilled in steam, and driedin vacuoover solid calcium nitrate, and then over solid caustic baryta.
Iodine is a greyish-black shining solid, possessing a metallic lustre and having somewhat the appearance of graphite. Its specific gravity is 4.948 (17°/4°). It melts at 114.2° C. and boils at 184.35° C. under atmospheric pressure (W. Ramsay and S. Young). The specific heat of solid iodine is 0.0541 (H. Kopp). Its latent heat of fusion is 11.7 calories, and its latent heat of vaporization is 23.95 calories (P. A. Favre and J. T. Silbermann). The specific heat of iodine vapour at constant pressure is 0.03489, and at constant volume 0.02697. It volatilizes slowly at ordinary temperatures, but rapidly on heating. Iodine vapour on heating passes from a violet colour to a deep indigo blue; this behaviour was investigated by V. Meyer (Ber., 1880, 13, p. 394), who found that the change of colour was accompanied by a change of vapour density. Thus, the density of air being taken as unity, Victor Meyer found the following values for the density of iodine vapour at different temperatures:—
This shows that the iodine molecule becomes less complex in structure at higher temperatures.
Iodine possesses a characteristic penetrating smell, not so pungent, however, as that of chlorine or bromine. It is only very sparingly soluble in water, but dissolves readily in solutions of the alkaline iodides and in alcohol, ether, carbon bisulphide, chloroform, and many liquid hydrocarbons. Its solutions in the alkaline iodides and in alcohol and ether are brown in colour, whilst in chloroform and carbon bisulphide the solution is violet. It appears to combine with the solvent (P. Waentig,Zeit. phys. Chem., 1909, p. 513). Its chemical properties closely resemble those of chlorine and bromine; its affinity for other elements, however, is as a rule less than that of either. It will only combine with hydrogen in the presence of a catalyst, but combines with many other elements directly; for example, phosphorus melts and then inflames, antimony burns in the vapour, and mercury when heated with iodine combines with it rapidly. It is completely oxidized to iodic acid when boiled with fuming nitric acid. It is soluble in a solution of caustic potash, a dilute solution most probably containing the hypoiodite, which, however, changes slowly into iodate, the change taking place rapidly on warming. When alkali is added to aqueous iodine, followed immediately by either soda water or sodium bicarbonate, most of the original iodine is precipitated (R. L. Taylor,Jour. Chem. Soc., 1897, 71, p. 725, and K. J. P. Orton,ibid.p. 830). Iodine can be readily detected by the characteristic blue coloration that it immediately gives with starch paste; the colour is destroyed on heating, but returns on cooling provided the heating has not been too prolonged. Iodine in the presence of water frequently acts as an oxidizing agent; thus arsenious acid and the arsenites, on the addition of iodine solution, are converted into arsenic acid and arsenates. A dilute solution of iodine prevents the decomposition of hydrogen peroxide bycolloidal platinum (G. Bredig,Zeit. phys. Chem., 1899, 31, p. 258; 1901, 37, p. 323).
Iodine finds application in organic chemistry, forming addition products with unsaturated compounds, the combination, however, being more slow than in the case of chlorine or bromine. It rarely substitutes directly, because the hydriodic acid produced reverses the reaction; this can be avoided by the presence of precipitated mercuric oxide or iodic acid, which react with the hydriodic acid as fast as it is formed, and consequently remove it from the reacting system. As a rule it is preferable to use iodine in the presence of a carrier, such as amorphous phosphorus or ferrous iodide or to use it with a solvent. It is found that most organic compounds containing the grouping CH3·CO·C— or CH3·CH(OH)·C— in the presence of iodine and alkali give iodoform CHI3.
Hydriodic acid, HI, is formed by the direct union of its components in the presence of a catalytic agent; for this purpose platinum black is used, and the hydrogen and iodine vapour are passed over the heated substance. On shaking up iodine with a solution of sulphuretted hydrogen in water, a solution of hydriodic acid is obtained, sulphur being at the same time precipitated. The acid cannot be prepared by the action of concentrated sulphuric acid on an iodide on account of secondary reactions taking place, which result in the formation of free iodine and sulphur dioxide. The usual method is to make a mixture of amorphous phosphorus and a large excess of iodine and then to allow water to drop slowly upon it; the reaction starts readily, and the gas obtained can be freed from any admixed iodine vapour by passing it through a tube containing some amorphous phosphorus. It is a colourless sharp-smelling gas which fumes strongly on exposure to air. It readily liquefies at 0° C. under a pressure of four atmospheres, the liquefied acid boiling at −34.14° C. (730.4 mm.); it can also be obtained as a solid melting at −50.8° C. It is readily soluble in water, one volume of water at 10° C. dissolving 425 volumes of the acid. The saturated aqueous solution is colourless and fumes strongly on exposure to air; after a time it darkens in colour owing to liberation of iodine. The gas is readily decomposed by heat into its constituent elements. It is a powerful reducing agent, and is frequently employed for this purpose in organic chemistry; thus hydroxy acids are readily reduced on heating with the concentrated acid, and nitro compounds are reduced to amino compounds, &c. It is preferable to use the acid in the presence of amorphous phosphorus, for the iodine liberated during the reduction is then utilized in forming more hydriodic acid, and consequently the original amount of acid goes much further. It forms addition compounds with unsaturated compounds.It has all the characteristics of an acid, dissolving many metals with evolution of hydrogen and formation of salts, callediodides. The iodides can be prepared either by direct union of iodine with a metal, from hydriodic acid and a metal, oxide, hydroxide or carbonate, or by action of iodine on some metallic hydroxides or carbonates (such as those of potassium, sodium, barium, &c.; other products, however, are formed at the same time). The iodides as a class resemble the chlorides and bromides, but are less fusible and volatile. Silver iodide, mercurous iodide, and mercuric iodide are insoluble in water; lead iodide is sparingly soluble, whilst most of the other metallic iodides are soluble. Strong heating decomposes the majority of the iodides. Nitrous acid and chlorine readily decompose them with liberation of iodine; the same effect being produced when they are heated with concentrated sulphuric acid and manganese dioxide. The soluble iodides, on the addition of silver nitrate to their nitric acid solution, give a yellow precipitate of silver iodide, which is insoluble in ammonia solution. Hydriodic acid and the iodides may be estimated by conversion into silver iodide.Iodine combines with chlorine to formiodine monochloride, ICl, which may be obtained by passing dry chlorine over dry iodine until the iodine is completely liquefied, or according to R. Bunsen by boiling iodine withaqua regiaand extracting with ether. It exists in two different crystalline forms, the more stable or α form melting at 27.2° C., and the less stable or β form melting at 13.9° C. It is readily decomposed by water. Thetrichloride, ICl3, results from the action of excess of chlorine on iodine, or from iodic acid and hydrochloric acid, or by heating iodine pentoxide with phosphorus pentachloride. It crystallizes in long yellow needles and decomposes readily on heating into the monochloride and chlorine. It is readily soluble in water, but excess of water decomposes it. (See W. Stortenbeker,Zeit. phys. Chem., 1889, 3, p. 11.) Iodine monochloride in glacial acetic acid solution was used by A. Michael and T. H. Norton (Ber., 1876, 9, p. 1752) for the preparation of paraiodo-acetanilide.Iodine Pentoxide, I2O5, the best-known oxide, is obtained as a white crystalline solid by heating iodic acid to 170° C.; it is easily soluble in water, combining with the water to regenerate iodic acid; and when heated to 300° C. it breaks up into its constituent elements, (see M. Guichard,Compt. rend., 1909, 148, p. 925.) Iodine dioxide, I2O4, obtained by Millon, and reinvestigated by M. M. P. Muir (Jour. Chem. Soc., 1909, 95, p. 656), is a lemon-yellow solid obtained by acting on iodic acid with sulphuric acid, oxygen being evolved. By acting with ozone on a chloroform solution of iodine, F. Fichter and F. Rohner (Ber., 1909, 42, p. 4093) obtained a yellowish white oxide, of the formula I4O9, which they regard as an iodate of tervalent iodine, Millon’s oxide being considered a basic iodate.Althoughhypoiodous acidis not known, it is extremely probable that on adding iodine or iodine monochloride to a dilute solution of a caustic alkali, hypoiodites are formed, the solution obtained having a characteristic smell of iodoform, and being of a pale yellow colour. It oxidizes arsenites, sulphites and thiosulphates immediately. The solution is readily decomposed on the addition of sodium or potassium bicarbonates, with liberation of iodine. The hypoiodite disappears gradually on standing, and rapidly on warming, being converted into iodate (see R. L. Taylor,Jour. Chem. Soc., 1897, 71, p. 725, and K. J. P. Orton,ibid.p. 830). The peculiar nature of the action between iodine and chlorine in aqueous solution has led to the suggestion that the product is a base,i.e.iodine hydroxide. Tri-iodine hydroxide, I3·OH, is obtained by oxidizing potassium iodide with sulphuric acid and potassium permanganate (A. Skrabal and F. Buchter,Chem. Zeit., 1909, 33, pp. 1184, 1193).Iodic Acid, HIO3, can be prepared by dissolving iodine pentoxide in water; by boiling iodine with fuming nitric acid, 6I + 10HNO3= 6HIO3+ 10NO + 2H2O; by decomposing barium iodate with the calculated quantity of sulphuric acid, previously diluted with water, or by suspending iodine in water and passing in chlorine, I2+ 5Cl2+ 6H2O = 2HIO3+ 10HCl. It is a white crystalline solid, easily soluble in water, the solution showing a strongly acid reaction with litmus; the colour, however, is ultimately discharged by the bleaching power of the compound. It is a most powerful oxidizing agent, phosphorus being readily oxidized to phosphoric acid, arsenic to arsenic acid, silicon at 250° C. to silica, and hydrochloric acid to chlorine and water. It is readily reduced, with separation of iodine, by sulphur dioxide, hydriodic acid or sulphuretted hydrogen, thus:—HIO3+ 5HI = 3H2O + 3I2; 2HIO3+5SO2+ 4H2O = 5H2SO4+ I2;2HIO3+ 5H2S = I2+ 5S + 6H2O.The salts, known as theiodates, can be prepared by the action of the acid on a base, or sometimes by the oxidation of iodine in the presence of a base. They are mostly insoluble or only very slightly soluble in water. The iodates of the alkali metals are, however, readily soluble in water (except potassium iodate). They are more easily reduced than the corresponding chlorates; an aqueous solution of hydriodic acid giving free iodine and a metallic oxide, whilst aqueous hydrochloric acid gives iodine trichloride, chlorine, water and a chloride. They are decomposed on heating, with liberation of oxygen, in some cases leaving a residue of iodide and in others a residue of oxide of the metal, with liberation of iodine as well as of oxygen.Periodic Acid, HIO4·2H2O, is only known in the hydrated form. It can be prepared by the action of iodine on perchloric acid, or by boiling normal silver periodate with water: 2AgIO4+ 4H2O = Ag2H3IO6+ HIO4·2H2O. It is a colourless, crystalline, deliquescent solid which melts at 135° C., and at 140° C. is completely decomposed into iodine pentoxide, water and oxygen. The periodates are a very complex class of salts, and may be divided into four classes, namely, meta-periodates derived from the acid HIO4; meso-periodates from HIO4·H2O, para-periodates from HIO4·2H2O and the diperiodates from 2HIO4·H2O (see C. Kimmins,Jour. Chem. Soc., 1887, 51, p. 356).Iodine has extensive applications in volumetric analysis, being used more especially for the determination of copper.The atomic weight of iodine was determined by J. S. Stas, from the analysis of pure silver iodate, and by C. Marignac from the determinations of the ratios of silver to iodine, and of silver iodide to iodine; the mean value obtained for the atomic weight being 126.53. G. P. Baxter (Jour. Amer. Chem. Soc., 1904, 26, p. 1577; 1905, 27, p. 876; 1909, 31, p. 201), using the method of Marignac, obtained the value 126.985 (O = 16). P. Köthner and E. Aeuer (Ber., 1904, 37, p. 2536;Ann., 1904, 337, p. 362), who converted pure ethyl iodide into hydriodic acid and subsequently into silver iodide, which they then analysed, obtained the value 126.026 (H = 1); a discussion of this and other values gave as a mean 126.97 (O = 16).
Hydriodic acid, HI, is formed by the direct union of its components in the presence of a catalytic agent; for this purpose platinum black is used, and the hydrogen and iodine vapour are passed over the heated substance. On shaking up iodine with a solution of sulphuretted hydrogen in water, a solution of hydriodic acid is obtained, sulphur being at the same time precipitated. The acid cannot be prepared by the action of concentrated sulphuric acid on an iodide on account of secondary reactions taking place, which result in the formation of free iodine and sulphur dioxide. The usual method is to make a mixture of amorphous phosphorus and a large excess of iodine and then to allow water to drop slowly upon it; the reaction starts readily, and the gas obtained can be freed from any admixed iodine vapour by passing it through a tube containing some amorphous phosphorus. It is a colourless sharp-smelling gas which fumes strongly on exposure to air. It readily liquefies at 0° C. under a pressure of four atmospheres, the liquefied acid boiling at −34.14° C. (730.4 mm.); it can also be obtained as a solid melting at −50.8° C. It is readily soluble in water, one volume of water at 10° C. dissolving 425 volumes of the acid. The saturated aqueous solution is colourless and fumes strongly on exposure to air; after a time it darkens in colour owing to liberation of iodine. The gas is readily decomposed by heat into its constituent elements. It is a powerful reducing agent, and is frequently employed for this purpose in organic chemistry; thus hydroxy acids are readily reduced on heating with the concentrated acid, and nitro compounds are reduced to amino compounds, &c. It is preferable to use the acid in the presence of amorphous phosphorus, for the iodine liberated during the reduction is then utilized in forming more hydriodic acid, and consequently the original amount of acid goes much further. It forms addition compounds with unsaturated compounds.
It has all the characteristics of an acid, dissolving many metals with evolution of hydrogen and formation of salts, callediodides. The iodides can be prepared either by direct union of iodine with a metal, from hydriodic acid and a metal, oxide, hydroxide or carbonate, or by action of iodine on some metallic hydroxides or carbonates (such as those of potassium, sodium, barium, &c.; other products, however, are formed at the same time). The iodides as a class resemble the chlorides and bromides, but are less fusible and volatile. Silver iodide, mercurous iodide, and mercuric iodide are insoluble in water; lead iodide is sparingly soluble, whilst most of the other metallic iodides are soluble. Strong heating decomposes the majority of the iodides. Nitrous acid and chlorine readily decompose them with liberation of iodine; the same effect being produced when they are heated with concentrated sulphuric acid and manganese dioxide. The soluble iodides, on the addition of silver nitrate to their nitric acid solution, give a yellow precipitate of silver iodide, which is insoluble in ammonia solution. Hydriodic acid and the iodides may be estimated by conversion into silver iodide.
Iodine combines with chlorine to formiodine monochloride, ICl, which may be obtained by passing dry chlorine over dry iodine until the iodine is completely liquefied, or according to R. Bunsen by boiling iodine withaqua regiaand extracting with ether. It exists in two different crystalline forms, the more stable or α form melting at 27.2° C., and the less stable or β form melting at 13.9° C. It is readily decomposed by water. Thetrichloride, ICl3, results from the action of excess of chlorine on iodine, or from iodic acid and hydrochloric acid, or by heating iodine pentoxide with phosphorus pentachloride. It crystallizes in long yellow needles and decomposes readily on heating into the monochloride and chlorine. It is readily soluble in water, but excess of water decomposes it. (See W. Stortenbeker,Zeit. phys. Chem., 1889, 3, p. 11.) Iodine monochloride in glacial acetic acid solution was used by A. Michael and T. H. Norton (Ber., 1876, 9, p. 1752) for the preparation of paraiodo-acetanilide.
Iodine Pentoxide, I2O5, the best-known oxide, is obtained as a white crystalline solid by heating iodic acid to 170° C.; it is easily soluble in water, combining with the water to regenerate iodic acid; and when heated to 300° C. it breaks up into its constituent elements, (see M. Guichard,Compt. rend., 1909, 148, p. 925.) Iodine dioxide, I2O4, obtained by Millon, and reinvestigated by M. M. P. Muir (Jour. Chem. Soc., 1909, 95, p. 656), is a lemon-yellow solid obtained by acting on iodic acid with sulphuric acid, oxygen being evolved. By acting with ozone on a chloroform solution of iodine, F. Fichter and F. Rohner (Ber., 1909, 42, p. 4093) obtained a yellowish white oxide, of the formula I4O9, which they regard as an iodate of tervalent iodine, Millon’s oxide being considered a basic iodate.
Althoughhypoiodous acidis not known, it is extremely probable that on adding iodine or iodine monochloride to a dilute solution of a caustic alkali, hypoiodites are formed, the solution obtained having a characteristic smell of iodoform, and being of a pale yellow colour. It oxidizes arsenites, sulphites and thiosulphates immediately. The solution is readily decomposed on the addition of sodium or potassium bicarbonates, with liberation of iodine. The hypoiodite disappears gradually on standing, and rapidly on warming, being converted into iodate (see R. L. Taylor,Jour. Chem. Soc., 1897, 71, p. 725, and K. J. P. Orton,ibid.p. 830). The peculiar nature of the action between iodine and chlorine in aqueous solution has led to the suggestion that the product is a base,i.e.iodine hydroxide. Tri-iodine hydroxide, I3·OH, is obtained by oxidizing potassium iodide with sulphuric acid and potassium permanganate (A. Skrabal and F. Buchter,Chem. Zeit., 1909, 33, pp. 1184, 1193).
Iodic Acid, HIO3, can be prepared by dissolving iodine pentoxide in water; by boiling iodine with fuming nitric acid, 6I + 10HNO3= 6HIO3+ 10NO + 2H2O; by decomposing barium iodate with the calculated quantity of sulphuric acid, previously diluted with water, or by suspending iodine in water and passing in chlorine, I2+ 5Cl2+ 6H2O = 2HIO3+ 10HCl. It is a white crystalline solid, easily soluble in water, the solution showing a strongly acid reaction with litmus; the colour, however, is ultimately discharged by the bleaching power of the compound. It is a most powerful oxidizing agent, phosphorus being readily oxidized to phosphoric acid, arsenic to arsenic acid, silicon at 250° C. to silica, and hydrochloric acid to chlorine and water. It is readily reduced, with separation of iodine, by sulphur dioxide, hydriodic acid or sulphuretted hydrogen, thus:—
HIO3+ 5HI = 3H2O + 3I2; 2HIO3+5SO2+ 4H2O = 5H2SO4+ I2;2HIO3+ 5H2S = I2+ 5S + 6H2O.
The salts, known as theiodates, can be prepared by the action of the acid on a base, or sometimes by the oxidation of iodine in the presence of a base. They are mostly insoluble or only very slightly soluble in water. The iodates of the alkali metals are, however, readily soluble in water (except potassium iodate). They are more easily reduced than the corresponding chlorates; an aqueous solution of hydriodic acid giving free iodine and a metallic oxide, whilst aqueous hydrochloric acid gives iodine trichloride, chlorine, water and a chloride. They are decomposed on heating, with liberation of oxygen, in some cases leaving a residue of iodide and in others a residue of oxide of the metal, with liberation of iodine as well as of oxygen.
Periodic Acid, HIO4·2H2O, is only known in the hydrated form. It can be prepared by the action of iodine on perchloric acid, or by boiling normal silver periodate with water: 2AgIO4+ 4H2O = Ag2H3IO6+ HIO4·2H2O. It is a colourless, crystalline, deliquescent solid which melts at 135° C., and at 140° C. is completely decomposed into iodine pentoxide, water and oxygen. The periodates are a very complex class of salts, and may be divided into four classes, namely, meta-periodates derived from the acid HIO4; meso-periodates from HIO4·H2O, para-periodates from HIO4·2H2O and the diperiodates from 2HIO4·H2O (see C. Kimmins,Jour. Chem. Soc., 1887, 51, p. 356).
Iodine has extensive applications in volumetric analysis, being used more especially for the determination of copper.
The atomic weight of iodine was determined by J. S. Stas, from the analysis of pure silver iodate, and by C. Marignac from the determinations of the ratios of silver to iodine, and of silver iodide to iodine; the mean value obtained for the atomic weight being 126.53. G. P. Baxter (Jour. Amer. Chem. Soc., 1904, 26, p. 1577; 1905, 27, p. 876; 1909, 31, p. 201), using the method of Marignac, obtained the value 126.985 (O = 16). P. Köthner and E. Aeuer (Ber., 1904, 37, p. 2536;Ann., 1904, 337, p. 362), who converted pure ethyl iodide into hydriodic acid and subsequently into silver iodide, which they then analysed, obtained the value 126.026 (H = 1); a discussion of this and other values gave as a mean 126.97 (O = 16).
Inmedicineiodine is frequently applied externally as a counter-irritant, having powerful antiseptic properties. In the form of certain salts iodine is very widely used, for internal administration in medicine and in the treatment of many conditions usually classed as surgical, such as the bone manifestations of tertiary syphilis. The most commonly used salt is the iodide of potassium; the iodides of sodium and ammonium are almost as frequently employed, and those of calcium and strontium are in occasional use. The usual doses of these salts are from five to thirty grains or more. Their pharmacological action is as obscure as their effects in certain diseased conditions are consistently brilliant and unexampled. Our ignorance of their mode of action is cloaked by the termdeobstruent, which implies that they possessthe power of driving out impurities from the blood and tissues. Most notably is this the case with the poisonous products of syphilis. In its tertiary stages—and also earlier—this disease yields in the most rapid and unmistakable fashion to iodides; so much so that the administration of these salts is at present the best means of determining whether, for instance, a cranial tumour be syphilitic or not. No surgeon would think of operating on such a case until iodides had been freely administered and, by failing to cure, had proved the disease to be non-syphilitic. Another instance of this deobstruent power—“alterative,” it was formerly termed—is seen in the case of chronic lead poisoning. The essential part of the medicinal treatment of this condition is the administration of iodides, which are able to decompose the insoluble albuminates of lead which have become locked up in the tissues, rapidly causing their degeneration, and to cause the excretion of the poisonous metal by means of the intestine and the kidneys. The following is a list of the principal conditions in which iodides are recognized to be of definite value: metallic poisonings, as by lead and mercury, asthma, aneurism, arteriosclerosis, angina pectoris, gout, goitre, syphilis, haemophilia, Bright’s disease (nephritis) and bronchitis.
Small quantities of the iodate (KIO3) are a frequent impurity in iodide of potassium, and cause the congeries of symptoms known asiodism. These comprise dyspepsia, skin eruption and the manifestations which are usually identified with a “cold in the head.” In many cases, as in syphilis, aneurism, lead poisoning, &c., the life of the patient depends on the free and continued use of the iodide, and this is best to be accomplished by securing an absolutely pure supply of the salt. Another often successful method of preventing the onset of symptoms of poisoning is to administer small doses of ammonium carbonate with the drug, thereby neutralizing the iodic acid which is liberated in the stomach.
Small quantities of the iodate (KIO3) are a frequent impurity in iodide of potassium, and cause the congeries of symptoms known asiodism. These comprise dyspepsia, skin eruption and the manifestations which are usually identified with a “cold in the head.” In many cases, as in syphilis, aneurism, lead poisoning, &c., the life of the patient depends on the free and continued use of the iodide, and this is best to be accomplished by securing an absolutely pure supply of the salt. Another often successful method of preventing the onset of symptoms of poisoning is to administer small doses of ammonium carbonate with the drug, thereby neutralizing the iodic acid which is liberated in the stomach.
IODOFORM,CHI3, a valuable antiseptic discovered by G. S. Sérullas in 1822; in 1834 J. B. Dumas showed that it contained hydrogen. It is formed by the action of iodine and aqueous potash on ethyl alcohol, acetone, acetaldehyde and from most compounds containing the grouping CH3·CO·C−. Its formation from alcohol may be represented thus: C2H5OH + 4I2+ 6KHO = CHI3+ KHCO2+ 5KI + 5H2O. It crystallizes in yellow hexagonal plates, melting at 119-120° C., and is readily soluble in alcohol and ether, but is insoluble in water. It has a characteristic odour and is volatile in steam. On reduction with hydriodic acid, it yields methylene iodide, CH2I2.
More recently, iodoform has been prepared by the electrolysis of a solution of potassium iodide in the presence of alcohol or acetone, the electrolytic cell being fitted with a diaphragm, in order to prevent the hydrogen which is formed at the same time from reducing the iodoform, or from combining with the iodine to form hydriodic acid. K. Elbs uses a solution of potassium iodide and sodium carbonate in water, which with the necessary alcohol is contained in a porous cell fitted with a lead anode, whilst the cathode compartment contains a solution of caustic soda and a nickel electrode. The electrolysis is carried out at a temperature of 70° C., and a current density of one ampère per square decimetre is used. At the end of three hours a yield of 70% of the theoretical quantity is obtained.
More recently, iodoform has been prepared by the electrolysis of a solution of potassium iodide in the presence of alcohol or acetone, the electrolytic cell being fitted with a diaphragm, in order to prevent the hydrogen which is formed at the same time from reducing the iodoform, or from combining with the iodine to form hydriodic acid. K. Elbs uses a solution of potassium iodide and sodium carbonate in water, which with the necessary alcohol is contained in a porous cell fitted with a lead anode, whilst the cathode compartment contains a solution of caustic soda and a nickel electrode. The electrolysis is carried out at a temperature of 70° C., and a current density of one ampère per square decimetre is used. At the end of three hours a yield of 70% of the theoretical quantity is obtained.
IOLA,a city and the county-seat of Allen county, Kansas, U.S.A., on the Neosho river, about 100 m. S. by W. of Kansas City. Pop. (1890) 1706; (1900) 5791, of whom 237 were foreign-born and 207 were negroes; (1905) 10,287; (1910) 9032. It is served by the Atchison, Topeka & Santa Fé, the Missouri Pacific and the Missouri, Kansas & Texas railways. It is pleasantly situated in a level valley where there is a great abundance of natural gas and some fine building stone. The city has large zinc smelters and zinc rolling-mills, a foundry, machine shops, and manufactories of cement, sulphuric acid and brick. The municipality owns and operates its waterworks, gas plant and electric-lighting plant. Iola was founded in 1859 by a company whose members were dissatisfied with the location of the county-seat at Humboldt. It became the county-seat in 1865, was chartered as a city of the third class in 1870 and became a city of the second class in 1898. The rapid growth of the city dates from the discovery of natural gas here, on Christmas Day 1893.
IOLITE,a mineral occasionally cut as a gem-stone, and named from the violet colour which it sometimes presents (ἴον, “violet”;λίθος, “stone”). It is generally called by petrographers cordierite, a name given by R. J. Haüy in honour of the French mineralogist, P. L. Cordier, who discovered its remarkable dichroism, and suggested for it the name dichroite, still sometimes used. The difference of colour which it shows in different directions is so marked as to be well seen without the dichroscope. The typical colours are deep blue, pale blue and yellowish grey. While the crystal as a whole shows these three colours, each face is dichroic.
Iolite is a hydrous magnesium and aluminium silicate, with ferrous iron partially replacing magnesium. It crystallizes in the orthorhombic system. In hardness and specific gravity it much resembles quartz. The transparent blue or violet variety used as a gem occurs as pebbles in the gravels of Ceylon, and bears in many cases a resemblance to sapphire. The paler kinds are often called water-sapphire (saphir d’eauof French jewellers) and the darker kinds lynx-sapphire; the shade of colour varying with the direction in which the stone is cut. From sapphire the iolite is readily distinguished by its stronger pleochroism, its lower density (about 2.6) and its inferior hardness (about 7).
Iolite occurs in granite and in true eruptive rocks, but is most characteristically developed as a product of contact metamorphism in gneiss and altered slates. A variety occurring at the contact of clay-slate and granite on the border of the provinces of Shimotsuké and Ködzuké in Japan has been called cerasite. It readily suffers chemical change, and gives rise to a number of alteration-products, of which pinite is a characteristic example.
Although iolite, or cordierite, is rather widely distributed as a constituent of certain rocks, fine crystals of the mineral are of very limited occurrence. One of the best-known localities is Bodenmais, in Bavaria, where it occurs with pyrrhotite in a granite matrix. It is found also in Norway, Sweden and Finland, in Saxony and in Switzerland. Large crystals are developed in veins of granite running through gneiss at Haddam, Connecticut; and it is known at many other localities in the United States.