PYRITES PYROMETER 109 The commerce is chiefly with Spain. It is di- vided into the arrondissements of Perpignan, Ceret, and Prades. Capital, Perpignan. PYRITES (Gr. wvpirw, from irvp, fire), a name given to yellow sulphuret of iron because it struck fire with steel. The German name Kies is similar to that for flint, Kiesel, and in the earliest firearms the powder was ignited by a piece of pyrites, the use of flints being later. It is now extended to sulphurets of other metals, and also to certain arsenides and dou- ble compounds of metals with sulphur. There are three kinds of iron pyrites : cubic or yel- low, marcite or white, and magnetic pyrites. The first two are isomeric, having the for- mula FeS-z, but are not isomorphous. Cubic py- rites crystallizes in several monometric forms, of which the cube, octahedron, and dodeca- hedron are the chief; while marcite belongs to the trimetric or rhombic system. Magnetic pyrites when pure has the formula Fe 7 S 8 , and crystallizes in the hexagonal system. Cubic or yellow pyrites, or mundic as it is called in Wales, is found in all geological formations, from the most ancient crystalline to recent al- luvial. Very large cubes have been found in some of the Cornish mines, dodecahedrons 6 in. in diameter in the island of Elba, and large octahedral crystals at Persberg in Sweden; in Connecticut, at Lane's mine in octahedrons, and at Orange and Milford in cubes in chlorite state ; and in Pennsylvania, at Cornwall, Leb- anon co., in cubo-octahedrons an inch in diam- eter. Cubic pyrites is largely used in the manufacture of copperas and sulphuric acid, and in Sweden for obtaining sublimed sulphur ; and enormous quantities are exported from Spain to Great Britain. Yellow pyrites, from its resemblance to the precious metal, by which many have been deceived, is sometimes called " fool's gold." In the chemical works of Yorkshire " coal brasses," as pyrites is called, are exposed in their beds, where by the action of air and moisture they are converted into copperas ; heat is developed during the process. In the coal fields subterranean fires are sometimes kindled by the conversion of masses of pyrites into copperas. At Quarrel- town in Renfrewshire, Scotland, is a deep hol- low where about 100 years ago the ground fell from a subterranean fire thus kindled. The conversion of pyrites into copperas is more conveniently conducted by roasting. (See SUL- PHUR, and SULPHURIC ACID.) Copper pyrites (calcopyrite of Dana) is the common copper ore of Cornwall, where from 10,000 to 12,000 tons of copper are smelted from 150,000 to 160,000 tons of ore. It is a double sulphuret of copper and iron, containing sulphur 84*9, copper 34' 6, iron 30 '5. It crystallizes in the dimetric system, often in tetrahedrons. Cop- per pyrites in massive crystals occurs at Ellen- ville, Ulster co., N. Y., composed of sulphur 36-65, copper 32*43, and iron 31-25. Fire py- rites is found in the Cornish mines having the following composition : sulphur 30'0, tin 27'2, copper 29-7, iron 13-1. Leucopyrite (Dana) is an arsenide of iron, and mispickle is a sul- phuret of arsenic. PIRMONT, a watering place of Waldeck, Germany, on the Emmer, 34 m. S. "W. of Han- over. It has chalybeate springs, is the capi- tal of the county of Pyruiont (pop. in 1871, 7,588), and contains a fine palace, a large bathing establishment, and a gas grotto emit- ting deadly vapors. PYROLIGNEOUS ACID (Gr. KV P , fire, and Lat. lignum, wood), also called pyroligneous and wood vinegar, the compound mixture of the volatile products from the destructive distilla- tion of woody matters, which when purified yield acetic acid, wood naphtha, creosote, tar, &c. The method of producing it is noticed in the article ACETIC ACID, vol. i., p. 62, as also its use in the crude state for furnishing com- pounds useful as mordants in calico print works, as pyrolignate of iron, alumina, &c. It has been applied to various other uses, as for example, in medicine, as an antiseptic and stimulant in a wash for gangrene and ulcers, although at present the more definite products, such as carbolic acid, are preferred. Its anti- septic qualities have led to its use in preserv- ing articles of food, as herrings and other fish. The process is auxiliary to drying in the shade, which precedes the dipping of the articles in the acid. Herrings first cured by a sprinkling of salt left upon them for six hours, and then drained, being immersed a few seconds in pyroligneous acid and then dried for two months, are in an excellent con- dition for preservation and retain a smoky fla- vor. The addition of a quart of the acid to the common pickle for a barrel of hams will cause the hams to acquire this flavor as if they had been smoked in the ordinary way. PYROMETER (Gr. nvp, fire, arid /serpov, mea- sure), any instrument for determining degrees of heat higher than those which can be mea- sured by ordinary thermometers. Pyrome- ters are required in the determination of the intensity of the heat of furnaces, and in as- certaining at what temperatures metals melt and chemical compounds are formed or are de- composed. They may be arranged, according to the principles on which they act, in the fol- lowing classes: 1, pyrometers using the expan- sion of solids as a means of measuring high temperatures, of which class Daniell's is a type ; 2, those using the contraction of baked clay, as Wedgwood's ; 3, those employing the expansion of air, as Pouillet's, Regnault's, and Jolly's; 4, those using the known melt- ing points of solids ; 5, those depending on the chemical decomposition of solids, as Lamy's; 6, those measuring temperatures by heating a known weight of water, by allowing to cool in it a known weight of platinum or other metal, which has been heated to the temperature of the space or of the body to be tested, as Pouillet's ; 7, those which determine tempera- tures from the measures of the strength of
