Page:EB1911 - Volume 22.djvu/714

dilute acid, ammonia is evolved, and an amorphous powder of variable composition, known as pyrrol-red, separates out. The pyrrol ring is easily broken, e.g. hydroxylamine gives the dioxime of succinic aldehyde. Pyrrol is readily converted into pyridine derivatives by acting with bromoform, chloroform, or methylene iodide on its potassium salt, β-brom-and β-chlorpyridine being obtained with the first two compounds, and pyridine itself with the last. Iodine in alkaline solution converts pyrrol into iodol (tetra-iodopyrrol), crystallizing in yellowish brown needles, which decompose on heating. It may also be prepared by heating tetra-brom- or tetra-chlorpyrrol with potassium iodide in alcoholic solution (German patent, 38423, 1886). It is used as an antiseptic.

Zinc dust and hydroc loric acid reduce pyrrol to pyrrolin (dihydropyrrol), C₄H₆·NH, a liquid which boils at 90° C. (748 mm.); it is soluble in water and has strongly basic properties and an alkaline reaction. Hydriodic acid at high temperature reduces pyrrol to pyrrolidine (tetra-hydropyrrol), C₄H₈NH. Pyrrolidine has also been prepared by A. Thiele (Ber. 1905, 38, p. 4154) from β-chlorpropionic aldehyde diethyl acetal. The chlorine atom in this compound is replaced by the cyano-group, which is then reduced to the CH₂NH₂. group and coupled up with benzene sulphochloride to form the compound C₆H₅SO₂NH(CH₂)₃·CH(OC₂H₅)₂. This substance easily splits out alcohol, and the ring compound then formed yields pyrrolidine on reduction by sodium in amyl alcohol solution. An α-pyrrolidine carboxylic acid and its hydroxy derivatives have been detected by E. Fischer among the products of hydrolysis of proteids. R. Willstatter (Ber. 1900, 33, p. 1164) obtained this acid by the action of a methyl alcoholic solution of ammonia on dibrompropylmalonic ester at 140° C., the diamide formed being then hydrolysed either by hydrochloric acid or baryta water:—

CH2·CBr(CO2H)2	→	CH2·(CONH2)2	NH→	CH2·CH(CO2H)	NH.
|		|		|
CH2·CH2Br		CH2——CH2		CH2———CH2

Numerous substitution derivatives of pyrrol are known. The N-derivatives are prepared by the action of alkyl halides and acid chlorides on potassium pyrrol. The C-derivatives have been prepared in various ways. L. Knorr, by the action of ammonia on aceto-acetic ester, obtained β-imidobutyric ester, which with nitrous acid yields α-isonitroso-β-imidobutyric ester, CH₃·C(:NH)·C(:N·OH)CO₂C₂H₅. Reduction of this ester leads to the formation of ammonia, hydroxylamine, and dimethyl pyrrol dicarboxylic ester,

HN	C(CH3) :	C·CO2R
		|
	C(CO2R:	C·CH3

He also found that diaceto succinic ester reacts with compounds of the type NH₂R(R=H, CH3, OH, NHC₆H₅, &c.) to form pyrrol derivatives:—

NH2R+	CH3·CO·	CH·CO2R	→RN	C(CH3)	:C·CO2R
		|			|
	CH3·CO·	CH·CO2R		C(CH3)	:C·CO2R

By using compounds of the type NH₂R and acetophenone acetoacetic ester C₆H₅CO·CH₂·CH(COCH₃)||:CO₂R, C. Paal obtained similar results. For the benzo-pyrrols see Indole.

PYRUVIC ACID, or Pyroracemic Acid, CH₃CO⋅CO₂H, an organic acid first obtained by J. Berzelius by the dry distillation of tartaric or racemic acids (Pogg. Ann., 1835, 36, p. 1). It may be prepared by boiling α-dichlorpropionic acid with silver oxide; by the hydrolysis of acetyl cyanide with hydrochloric acid (J. Claisen and J. Shadwell, Ber., 1878. 11, pp. 620, 1563); and by warming oxalacetic ester with a 10% solution of sulphuric acid. It is usually made by distilling tartaric acid with potassium bisulphate at about 200–250° C., the crude product being afterwards fractionated. It is a liquid which boils at about 165° C. (with partial decomposition); it may be solidified, and when pure melts at 13·6° C. (L. Simon Bull. Soc. Chim., 1895 [3],13, p. 335). It is readily soluble in water, alcohol and ether. It reduces ammoniacal silver solutions. When heated with hydrochloric acid to 100° C. it yields carbon dioxide and pyrotartaric acid, C₅H₈O₄, and when warmed with dilute sulphuric acid to 150° C. it gives carbon dioxide and acetaldehyde. Sodium amalgam or zinc and hydrochloric acid reduce it to lactic acid, whilst hydriodic acid gives propionic acid. It readily condenses with aromatic hydrocarbons in the presence of sulphuric acid. It is somewhat readily oxidized; nitric acid gives carbonic and oxalic acids, and chromic acid, carbonic and acetic acids. It forms a well-crystallized hydrazone with phenylhydrazine; and α-nitroso propionic acid with hydroxylamine. It is monobasic and yields salts which only crystallize with great difficulty; when liberated from these salts by a mineral acid it forms a syrupy nonvolatile mass. In aqueous solution it gives a red colour with ferric chloride. It shows characteristic ketone reactions, yielding a bisulphite compound and combining with hydrocyanic acid to form the nitrile of α-oxyisosuccinic acid. When warmed with baryta water it gives uvitic acid.

Pyruvic nitrile, or acetyl cyanide, CH₃CO⋅CN, may be prepared by the action of silver cyanide on acetyl chloride; or of acetyl chloride on nitrosoacetone (L. Claisen and O. Manasse, Ber., 1887, 20, p. 2196). It is a liquid which boils at 93° C. and with caustic alkalis polymerizes to diacetyldicyanide.

PYTHAGORAS (6th century B.C.), Greek philosopher, was, in all probability, a native of Samos or one of the neighbouring islands (others say a Tyrrhenian, a Syrian or a Tyrian), and the first part of his life may therefore be said to belong to that Ionian seaboard which had already witnessed the first development of philosophic thought in Greece (see Ionian School). The exact year of his birth has been variously placed between 586 and 569 B.C., but 582 may be taken as the most probable date. He was a pupil of Pherecydes (q.v.), and later of Hermodamas (Diog. Laërt. viii. 2). He left in Ionia the reputation of a learned and universally informed man. “Of all men Pythagoras, the son of Mnesarchus, was the most assiduous inquirer,” says Heracleitus, and then proceeds in his contemptuous fashion to brand his predecessor’s wisdom as only eclectically compiled information or polymath (πσλυμαθία). This accumulated wisdom, as well as most of the tenets of the Pythagorean school, was attributed in antiquity to the extensive travels of Pythagoras, which brought him in contact (so it was said) not only with the Egyptians, the Phoenicians, the Chaldaeans, the Jews and the Arabians, but also with the Druids of Gaul, the Persian Magi and the Brahmans. But these tales represent only the tendency of a later age to connect the beginnings of Greek speculation with the hoary religions and priesthoods of the East, There is no intrinsic improbability, however, in the statement of Isocrates (Laud. Busir. 28, p. 227 Steph.) that Pythagoras visited Egypt and other countries of the Mediterranean, for travel was one of the few ways of gathering knowledge. Some of the accounts (e.g. Callimachus) represent Pythagoras as deriving much of his mathematical knowledge from Egyptian sources, but, however it may have been with the practical beginnings of geometrical knowledge, the scientific development of mathematical principles can be shown to be an independent product of Greek genius. Some of the rules of the Pythagorean ritual have their Egyptian parallels, as Herodotus points out, but it does not necessarily follow that they were borrowed from that quarter, and he is certainly wrong in tracing the doctrine of metempsychosis (q.v.) to Egypt.

The historically important part of his career begins with his migration to Crotona, one of the Dorian colonies in the south of Italy, about the year 529. According to tradition, he was driven from Samos by the tyranny of Polycrates. At Crotona Pythagoras speedily became the centre of a Widespread and influential organization, which seems to have resembled a religious brotherhood or an association for the moral reformation of society much more than a philosophic school. Pythagoras appears, indeed, in all the accounts more as a moral reformer than as a speculative thinker or scientific teacher; and the doctrine of the school which is most clearly traceable to Pythagoras himself in the ethico-mystical doctrine of transmigration. The Pythagorean brotherhood had its rise in the Wave of religious revival which swept over Hellas in the 6th century B.C., and it had much in common with the Orphic communities which sought by rites and abstinences to purify the believer's soul and enable it to escape from “the wheel of birth.” Its aims were undoubtedly those of a religious order rather than a political league. But a private religious organization of this description had no place in the traditions of Greek life, and could only maintain itself by establishing “the rule of the saints” on a political basis. The Pythagoreans appear to have established their supremacy for a time over a considerable part of Magna Graecia,