PYR 



PT'RO-ACIPS. The prefix pyro is attached 

 to the products obtained by subjecting 

 organic acids to heat, which gives rise to 

 distinct classes of acids. 



Pt ROCH'ROA. A genus of heteromerons 

 Coleoptera of the Trachelide family. The 

 species are found in the spring in woods, 

 and their larvae live under the bark of 

 trees. 



PYRO-CIT'RIC ACID. A peculiar acid ob- 

 tained by subjecting citric acid to dry 

 distillation, saturating the acid liquor 

 which results with lime, and decomposing 

 the precipitate with oxalic acid. It is 

 therefore reckoned one of the pyracids. 



PTRO-CIT'HIC ETHER. A colourless and 

 transparent liquid, obtained by heat act- 

 ing on a mixture of citric acid, alcohol, 

 and sulphuric acids. Sp. gr. 1'04. 



PYRO-GAL'LIC ACID. An acid obtained 

 from gallic acid by heat. It sublimes in 

 crystalline plates, which are white and 

 brilliant, and contain no water. Soluble 

 in water. 



PYRO-KIN'IC ACID. An acid obtained by 

 heat from kinic acid. It passes over in a 

 liquid state, but crystallises in tufts, when 

 the liquor is filtered and evaporated. 



PYROLIG'NOUS ACID. Wood vinegar. 

 This acid liquid, which passes over during 

 the destructive distillation of wood, is 

 a mixture of various products, the most 

 abundant of which is acetic acid. This 

 liquor being rectified by a second distilla- 

 tion, the acetic acid passes over, conta- 

 minated with a minute portion of a brown 

 empyreumatic oil. This, from its smell, 

 was regarded for some time as a distinct 

 acid, and was accordingly called pyfolig- 

 nous acid (from m>{, fire, and lignum, 

 wood), and the salts which it formed were 

 in consequence termed pyrolignites. 



PYROLIG'NOCS SPIRIT. See PIHOXILIC 

 SPIRIT. 



PYRO-LITH'IC ACID, ) When uric or li- 



PYRO-U'RIC ACID. } thic acid concre- 

 tions are subjected to dry distillation, 

 silvery white plates of pyrolithate of am- 

 monia sublime. A solution of these, poured 

 into that of subacetate of lead, gives a 

 precipitate of pyrolithate of lead. The 

 precipitate being washed, and diffused 

 through water, into which passes a stream 

 of sulphuretted hydrogen, the pyrolithate 

 of lead is decomposed ; and the liquid be- 

 comes a solution of pyro-lithic or pyro- 

 iiric acid. Acicular crystals are obtained 

 by evaporation. 



PYRO-MAL'IC ACID, \ The liquid acid 



PYRO-SOH'BIC ACID, j which passes over 

 in subjecting malic or sorbic acid to dry 

 distillation, is so named. It affords crys- 

 tals by evaporation. 



PYRO'MANCY, from m^, fire, and f&en- 

 mct, prophecy. Divination by the fire of 

 ta< ancient sacrifice*. 



3 PYR 



PYRO-MECON'IC ACID. An ac.d obtained 

 when mecpnic or parameconic acid is dis- 

 tilled. It is soluble in water and alcohol, 

 and affords crystals when its solutions are 

 evaporated. 



PYKOM'ETER, from Tt/g, fire, and ftirfw, 

 measure. The name of an instrument for 

 measuring degrees of heat, higher than 

 the range of the mercurial thermometer, 

 as that of furnaces and the like. Wedge- 

 u-ood's Pyrometer consists of a metallic 

 groove or gauge, the sides of which gra- 

 dually converge ; pieces of very pure clay 

 are made into small cylinders, having one 

 side flattened, and being heated to red- 

 ness, they are made to fit the larger ex- 

 tremity of the groove. As it is a property 

 of clay to contract and become harder 

 by exposure to a high temperature (sup- 

 posed to be) in proportion to the heat to 

 which it is exposed, all that is necessary 

 to make an observation is, to subject one 

 of the cylinders of clay to the heat of the 

 furnace, and when it is again cooled, to 

 try how far it slides downwards in the 

 gauge, which is marked off into 240 parts 

 or degrees, each calculated to be equal to 

 130 of Fahrenheit's scale. The zero is 

 red heat, supposed to be 1077 Pah. 

 Daniels' Register Pyrometer con- 

 sists of two parts, the register 

 and scale. The register is a solid 

 bar of black-lead earthenware 

 highly baked. In this a hole is 

 drilled, into which a bar of 

 platinum or malleable iron (6 

 inches long) is put, which rests 

 against the bottom of the ca- 

 vity. A cylindrical bar of por- 

 celain (called the index) , is then 

 placed upon the top of the bar, 

 and confined in its situation by 

 a ring of platinum. This ar- 

 rangement being subjected to 

 an increase of temperature, the 

 metal rod expands and forces 

 the index to recede, and the 

 amount of displacement being 

 noted, the temperature is known by the 

 scale on the index. 



PYRO-MU'CIC AI;ID An acid obtained 

 by distilling mucic acid in a retort. The 

 matter which comes over is mixed with 

 four times its weight of water, and then 

 evaporated, when the pyromucic acid is 

 deposited in crystals. It forms soluble 

 and crystallisable salts called pyromucates. 

 PYROPH'ANE, from trwj, fire, and tfatot, 

 clear. A mineral which in its natural 

 state is opaque, but is rendered transpa- 

 rent by heat. 



PYROPH'ORUS, from ?mg, fire, and fo{o<, 

 bearing. A generic name for any che- 

 mical preparation which becomes ignited 

 on exposure to the air. Several such 

 substances are prepared, mostly, however. 



