X XThe twenty-fourth letter and nine- teenth consonant in the English al- phabet. The form X is probably a Greek variant of /<(H (T). This form (X) had two different values in the alphabets of Eastern and West- •ern Greece. It is from the Western Greek alpha- bet that the Latin form and value (/cs) were de- rived. In native Latin words x never occurred initially, but it was employed internally as a representative of cs, gs, for example pax, pads, rexi, regere. Sound and Philological Value. As a pho- netic character X is the breathed velar spirant. In forming it the glottis is suddenly opened or closed on the passing of a breath. As a com- posite sound X has usually the value of ks, for example in fixture, Stijx, excellent. Between vowels, the second of which is accented, x be- comes soriantized (^ g:), as in exalt, crliilarate, exotic. In anxious, luxurious, x is pronounced hsli, gch. Initially, where it usually indicates a word of Greek origin, its sound is Z, as in Xaii- tippe, Xerxes, xylophone. As a philological de- rivative, English X represents Indo-Gcrmanie Is (Germanic hs), as in Sanskrit uksan, German Ochse, English ox; Greek f{; Latin sex, Ger- man seeks, English six. X occurs in loan-words from: (1) Latin, exact, tnix, tioxious; (2) from Greek onyx, calyx, lynx. As a Symbol axd Abbreviation. As a Roman numeral X = 10; y, = 1000; X = 10.000. In algelira x rc])resents an unknown varialile quantity; in analytical geometry x indicates the abscissa of the rectilinear coordinates. XALAPA, iia-lii'pa. Another spelling for Jalapa (q.v.), a citj' of Mexico. XALISCO, Ha-les'k6. Another spelling for Jalisco (q.v.), a State of Mexico. XANTHI, ziln'te. A town of European Turkey in the Vilayet of Adrianople. situated near an inlet of the ^Egean Sea, 200 mih:'s west of Constantinople. It is chiefly important for its trade in a celebrated brand of tobacco. Popula- tion, aliout 14,000. XANTHIN (from Gk. ^av06c. xanthos. yel- low). CjHjNjO,. An organic substance found in small quantities in urine and in the substance of the muscles, the livjr, the spleen, the brain, etc. It is also found in urinary calculi and in certain vegetable tissues (for instance, in tea). Somewhat large quantities of it are found in meat-extract. It is usually prepared from guanin, a nitrogenous substance allied to xanthin and obtained from guano; guanin is converted into xanthin by the action of nitrous acid and the subsequent reduction with ferrous sulphate in ammoniacal solution. Pure xanthin is a color- less .substance, soluble in alkalies, sparingly soluble in water, and acting as a feeble base. By the action of methyl iodide on its lead salt, theobromin — a substance closely allied to xan- thin — is obtained. The chemical constitution of xanthin has been shown by Fischer to be repre- sented by the following structural formula : NH — C = N CO C— XH
C CO NH — CH When oxidized, xanthin yields urea and allox- an, which are also among the oxidation prod- ucts of uric acid (q.v.). Xanthin may be iden- tified by a reaction similar to the murexid test for uric acid: a little nitric acid is added and a gentle heat applied till a dry residue is obtained; if a drop of caustic soda is added to the latter and heat applied, a permanent reddish-violet col- oration is produced, while in the case of uric acid the coloration disappears on warming. Xanthin is in most cases accompanied by hy- poxanthin, a similar substance, from which it may be separated by means of silver nitrate and nitric acid, xanthin-silver-nitrate (f'sHjNiO,. AgXO,) being more readily soluble in hot nitric acid than the analogous compound of hypo- xanthin. XANTHIPPE, z.an-thip'pe (Lat., from Gk. SavdiTnrri). The wife of the Athenian philos- opher Socrates. Her name has become proverbial for a typical termagant, and many stories have come down to ns ilhistrative of her shrewish temper. Several of these, however, may be of later invention, and. in judging her character, some allowance should perhaps be made for the unpractical and unconventional ways of Socrates, which could hardly have been other than exas- perating. Her grief and solicitude at the time of Socrates's imprisonment were, it is recorded, great. XANTHITJM. See Cocklebub. 639
