NISIBIS 



NITRIC ACID 



507 



trade iu turquoises. It was the birthplace, and 

 contains the grave, of Omar Khayyam. 



Xi sibis, the capital of ancient Mygdonia, the 

 north-eastern part of Mesopotamia, was a city of 

 great antiquity, and was of importance both as a 

 place of strength and as an emporium of the trade 

 between the east and west. It was twice taken by 

 the Romans (under Lucnllus and Trajan), and 

 again given up by them to the Armenians ; but 

 being a third time taken, in 165 A.D., it remained 

 the chief bulwark of the Roman empire against the 

 Persians, till it was surrendered to them after the 

 death of Julian in 363. The name Nisibin is re- 

 tained by a small village in the Turkish province 

 of Diarbekir, round which are numerous remains of 

 the ancient city. 



Nisi prius is the name (borrowed from the 

 first two words of the old writ which summoned 

 juries) usually given in England to the sittings of 

 juries in civil cases. Tim-, a judge sitting at nisi 

 priiis means a judge presiding at a jurj trial in a 

 civil cause, and a nisi prius lawyer is one who 

 devotes himself to jury practice. For the decree 

 nisi, see DIVORCE. 



Nitll. a beautiful Scottish river, rising in Ayr- 

 shire, and flowing 71 miles south-south-eastward 

 (mainly through Dumfriesshire), until, 14 miles 

 below Dumfries, its estuary joins the Solway Firth. 



Nifhsilalf. WILLIAM MAXWELL, EARL OF, 

 was liorn in 1676, and at seven succeeded his father 

 as fifth earl. In 1699 he married at Paris Lady 

 Winifred Herbert(c. 1679-1749), youngest daughter 

 of the Marquis of Powis, and thenceforward lived 

 almost constantly at his Kirkcudbrightshire seat, 

 Terregles, much embarrassed in circumstances, and 

 sorely troubled as a Catholic by the neighbouring 

 Presbyterian ministers. In 171- r > 'Nithsdale'sbonnie 

 lord' at once joined the English Jacobites under 

 Forster and Derwentwater, and was taken prisoner 

 at Preston. He was tried for high-treason in 

 London, and sentenced to death in spite of abject 

 excuses ; but on 23.1 February 1716 the night 

 liefore the day fixed for his execution not knowing 

 he had just been reprieved, he escaped from the 

 Tower in woman's apparel, through the heroism of 

 his countess. Naturally delicate and then advanced 

 in pregnancy, she had ridden up to London in the 

 depth of winter ; and after her lord's escape she 

 came back to Terregles, and dug up the family 

 deeds, which she had buried in the garden, and by 

 one of which the estates had been disponed in 1712 

 to their only son. They now settled at Koine, 

 where the earl died on 20th March 1744. See Sir 

 W. Fraser's Hook of Cartaveroclc (2 vols. 1873). 



Nitrates. See NITRE, NITRIC ACID, NITRI- 

 FICATION, MANURE. 



Nitre* or SALTPETRE (Lat. sal petrce, 'salt of 

 the rock,' through Old French), is the nitrate of 

 potash, KNOs. It usually occurs in long, colour- 

 less, striated, six-sided prisms ; its taste is cooling, 

 and very saline; it is soluble in seven times its 

 weight of water at 60 (15 '5 C.), and in less than 

 one-third of its weight of boiling water, but is 

 insoluble in alcohol. When heated to alxnit 660 

 (348" C. ) it fuses without decomposition into a thin 

 liquid, which, when cast in moulds, solidifies into 

 a white, fibrous, translucent mass, known as sal 

 prunelle. At a higher temperature part of the 

 oxygen is evolved, and nitrate of potash is formed. 

 Owing to the facility with which nitre parts with 

 its oxygen, it is much employed as an oxidising 

 agent. Mixtures of nitre and carbon, or of nitre 

 and sulphur, or of nitre, carbon, and sulphur, 

 deflagrate on the application of heat with great 

 energy ; and if nitre be thrown on glowing coals 

 it produces a brisk scintillation. Touch-paper is 



formed by dipping paper in a solution of nitre, and 

 drying it. 



Nitre occurs as a natural product in India and 

 Persia, where it is found sometimes as an efflores- 

 cence upon the soil, and sometimes disseminated 

 through its upper stratum. The crude salt is 

 obtained by lixiviating the soil, and allowing the 

 solution to crystallise. Much nitre used to be 

 artificially formed in Europe by imitating the 

 conditions under which it is naturally produced. 

 Animal matter, mingled with ashes and lime 

 rubbish, is placed in loosely aggregated heaps, 

 exposed to the air, but sheltered from rain. The 

 heaps are watered from time to time with urine or 

 stable runnings ; at suitable intervals the earth is 

 lixiviated, and the salt crystallised. As there is 

 always a considerable quantity of the nitrates of 

 lime and magnesia present, which will not crystal- 

 lise, carbonate of potash, in the shape of wood- 

 ashes, is added so long as any precipitate occurs. 

 The nitrate of lime is decomposed, and the insoluble 

 carlxmate of lime separated. The clear liquor is 

 then evaporated and crystallised. But the bulk of 

 the nitre of commerce is now made from the Chilian 

 nitrate of soda by double decomposition. The 

 common varieties of Indian nitre, which have a 

 dirty yellowish appearance, are termed rough or 

 crude saltpetre, while the purer kinds are called 

 East India refined. The purification or refining of 

 nitre is effected by dissolving it in water, boiling 

 the solution, removing the scum, straining it while 

 hot, ami setting it aside to crystallise. The most 

 common impurities are sulphate of potash, chlorides 

 of sodium and potassium, and nitrate of lime. 

 Chloride of barium will detect the first of these 

 impurities, nitrate of silver the second, and oxalate 

 of ammonia the third. 



Nitre is employed in the manufacture of sul- 

 phuric acid, in the preparation of nitric acid, as an 

 oxidising agent in numerous chemical processes, as 

 an ingredient of fireworks, and especially in the 

 manufacture of gunpowder. It is used in medicine. 

 In moderate doses (from ten grains to a scruple) it 

 acts as a refrigerant, diuretic, and diaphoretic, and 

 hence its use is indicated when we wish to diminish 

 abnormal heat, and to reduce the action of the 

 pulse, as in febrile disorders and hemorrhages. In 

 acute rheumatism it is given in large doses with 

 great benefit. It is a popular remedy in sore 

 throat, in the form of nitre balls, which should be 

 retained in the mouth till it melts, and the saliva 

 impregnated with it gently swallowed. The in- 

 halation of the fumes produced by the ignition of 

 touch-paper often gives speedy relief in cases of 

 spasmodic asthma. 



Cubic Nitre, or Nitrate of Soda, NaNO :) , occurs 

 abundantly on the surface of the soil in Chili and 

 Peru (especially Atacama and Tarapacd). It 

 derives its name from its crystallising in cube-like 

 rhombohed rons. In most of its properties it re- 

 sembles ordinary nitre, but, in consequence of its 

 greater deliquescence, it cannot be substituted for 

 that salt in the preparation of gunpowder. Being 

 considerably cheaper than the potash-salt, cubic 

 nitre is often substituted for it in the manufacture 

 of nitric and sulphuric acids ; and it is largely 

 used in agriculture (see MANURE). In 1882 the 

 amount shipped from South American ports was 

 stated at 476,000 tons ; in 1889, at 930,000. See 

 W. H. Russell's Visit to Chili and the Nitrate 

 Fields of Tarapacd (1890). For the Sweet Spirits 

 of Nitre, see NITROUS ETHER. 



\i t rian Desert. See NATRON LAKES. 



Nitric Acid is the most important of the five 

 compounds which oxygen forms with Nitrogen 

 (q.v.). Until 1849 it was known only in the 

 hy drated form ( the aquafortis of the older chemists), 



