Page:The New International Encyclopædia 1st ed. v. 18.djvu/390

SOLUTION. 33(5 SOUA. units of compounds— their molecular weights. (See CuEMiSTRY; Molecules — Moleculab Weights ; Avogadro's Rui.e ; Atomic Weights ; Gases, General Properties of; etc.) Yet a majority of compounds are non-volatile, and therefore our theoretical knowledge of them re- mained uncertain, and in many cases vague, until the above results proved that what we can learn of a substance by studying it in the gaseous state we can learn with equal certainty by studying it in dilute solution. Very few indeed are the sub- stances that are neither volatile nor soluble in any liquid. Direct methods for measuring osmotic pressure, like the one described above, have been of importance only in demonstrating the funda- mental laws; the experimental difficulties in- volved render their use for determinations of molecular weights practically impossible. But, on the other hand, it has been shown that the depression of the freezing-point or the elevation of the boiling point caused by dissolving a sub- stance in a given liquid is proportional to the osmotic pressure in the solution ; and so. molecu- lar weights are now generally determined by ob- serving the freezing-points or the boiling-points of solutions. (See Molecules — Molecular Weights ; Freezimg-Poikt : Boiling-Point. ) At first, experimental research seemed to sliow that compoimds of three important classes, viz. acids, bases, and salts, do not obey the laws of osmotic pressure; their osmotic pressure was found to be much higher than it should be theoretically. But Arrhenius's theory of elec- trolytic dissociation (see Dissociation) soon came to add itself to the theory of osmotic pres- sure, and, instead of disproving it, only furnished further proof of its correctness, just as the phe- nomena of chemical dissociation, when correctly understood, had once furnished additional proof of the rclial)ility of Avogadro's rule for gases. See Avog.dro's Rule. Histort. The history of our subject com- mences perhaps with Graham's researches on the difl'usion of substances in solution, dating back to 1S51. Ten years later Graham investigated the well-known method of dialysis, based on the fact-tliat many animal and vegetable membranes are permealile to water and the so-called 'crystal- loids,' but impermeable to 'colloids' (q.v. ). In IS07 Traube discovered that copper ferrocyanide is permeable to water, but inipcriiiealile to sugar, and more or less impcrmealjle to many other sub- stances. Ten years later Pfefl'er published the researches mentioned above tOsmotische Unter- siichiingen, Leipzig. 1877). Finally, in 1886. on the basis principally of the experimental re- searches of Pfeffer, De Vries, and Raoult, Van't Hoff worked out the theory of dilute solutions, which has extended the domain of rational chem- istry as few general ideas had done before. The principal names connected with the further de- velopment of the theory are those of Nernst. Ost- wald, and Arrhenius. In this country Arthur A. Xoyes has made a luimber of original contribu- tions of recognized importance. For an account of the physiological importance of osmotic phe- nomena, see Osmosis. SOL'WAY FIRTH. An inlet of the Irish Sea. separating f'unibprland from Scotland, and forminET in its upper part the estnarv of the Esk (Map: Scotland, E 5). Its length is 33 miles and its width increases gradunllv. although irregularly, to upward of 20 miles. It is noted for its spring tides, which rush in as a bore from three to six feet high at the rate of eight to ten miles an hour. SOL'YMAN (or SULEIMAN) II. (c.l495- IflGG). Sultan of the Turkish Empire, surnamed 'The Magnificent.' In September, 1520, he suc- ceeded his father, Selim I. (q.v.). He overthrew the rebellious governor of Syria, repressed the Egj'ptian Mamelukes, and concluded a treaty with Persia. In 1521 he took Belgrade, the key to Hungary. He next drove the Knights of Saint John from Rhodes (1522) after a five months' siege. In the succeeding years he devoted himself to improvements in the administration and to military preparations for a great onslaught upon Hungary. On August 29, 1526, he overwhelmed the army of King Louis II. at Mohacs. (See HuNG.RY. ) In 1520 he was summoned to Hun- gary in aid of his protege, John Zapolya, Way- wode of Transylvania, who was contesting the crown with Ferdinand, brother of the Emperor Charles V. He invaded that country with a great army, and laid siege to Vienna, but after a nvun- ber of unsuccessful assaults he was compelled to retreat. In 1532 he laid Styria waste and again advanced to the neighboi'hood of Vienna, but his arms were baffled bj' the resistance of the little Hungarian fortress of GUns, and the advance of the Imperial army under Charles V. forced him to retreat. Soon after this the Sultan waged a successful war against Persia. In 1535 Solyman concluded with Francis I. the famous treaty which opened the commerce of the Levant to the French flag alone. By 1541 the Turks were in permanent possession of the heart of Hungary. In 1542 the combined French and Turkish fleets ravaged the Italian coasts and pillaged Nice. The Turks were now sujireme in the Mediter- ranean; in 1551 Tripoli fell into their hands. A second and third war with Persia, which was now in a state of semi-subjugation, a brilliant naval victory (1561) over the Knights of Malta and their allies, the Spaniards, an unsuccessful siege of Malta (1565), and a fresh expedition to Hungary (1566), were the chief events of the remainder of Solyman's reign. He died during this last ex])edition, while besieging the little town of Sziget (whose defenders had stayed the advance of the Turkish host) September 5, 1566. Solyman encouraged literature, and did much for the improvement of the laws as well as for the military organization of the State. He was a ruler of many great qualities, and under him the Ottoman Empire reached the height of its power. Consult the works referred to under Turkey. SOMA (Skt.. from sii. to press). An Oriental plant identified, but not certainly, with the firircostemma aciduiii. It was at first deified in India on account of the intoxicating nature of its juice, and was then identified as a divine being with the moon, which it resembled in color and in its swelling, as well as in its magical maddening effect. The plant is plucked up by the roots by moonlight in the moun- tains and is crushed between two stones, after being carried on a goat-ear to the place of sacrifice. It is then strained through a sieve into a tub. where it is allowed to ferment ; and being thickened with meal and sweetened, it is drunk by the priests after being offered to