ACHATES 



ACID 



Peloponnesus, who formed one of the four 

 groups of ancient Greeks. After the Dorian 

 invasion they pushed into Northwestern 

 Greece, where they formed the Achaean 

 League, a confederation of the twelve towns of 

 that region. The power of the League waned 

 after the death of Alexander the Great. It 

 revived in 280 B. c. and later spread over 

 the whole of Greece, lasting until 146 B. c., 

 when it was destroyed by the Romans. The 

 term Achaia, or Achaea, was used by Horace 

 to designate the whole of Greece. The Achae- 

 ans received their name from their mytho- 

 logical ancestor, Achaeus, the grandson of 

 Hellen. See GREECE. 



ACHATES, aka' teez, one of the Trojans 

 who followed Aeneas and remained with him 

 through all his wanderings and his struggles 

 after the hurried flight from Troy (see TROY). 

 He was so devoted to Aeneas and so constant 

 that he was always called fidus (faithful), and 

 the expression fidus Achates has come to be a 

 common one for a very faithful friend. Scott 

 used the term in the sentence, "He has chosen 

 this fellow for his fidus Achates." 



ACHERON, ak' e ron, the name applied in 

 ancient times to a number of rivers in Greece 

 and Italy. In Homer's epics there is mention 

 of a river in the underworld by the name of 

 Acheron; the poet is said to have taken the 

 name from that of a river in Epirus which flows 

 into the Ionian Sea. In later mythology 

 Acheron is the name of a river or lake in 

 Pluto's realm, across which Charon ferried the 

 souls of the departed. See CHARON ; PLUTO. 



ACHILLES, akil' eez. The Iliad opens 

 with an account of the wrath of this great 

 Greek hero "ruinous wrath, which laid un- 

 numbered woes on the Grecians." He was the 

 son of Peleus and the sea-goddess Thetis. 

 Having been well trained in 

 the arts of war, when the 

 Trojan War broke out he 

 joined the Greek army, and 

 during the early years of 

 that struggle he was of great 

 help to the Greeks. How- 

 ever, when Agamemnon, 

 leader of the expedition, 

 took from him 

 Briseis, a cap- 

 tive maiden, he 

 refused to have 

 anything fur- TENDON OP ACHILLES 

 ther to do with Shown at " 



the war, and the Greeks soon were in des- 



perate straits. Only the death of his beloved 

 friend and kinsman Patroclus made Achilles 

 forget his personal grievances. Filled with 

 the desire for revenge, he rejoined his war- 

 ring countrymen and turned the tide of their 

 fortunes by slaying Hector, the bravest of 

 the Trojans. According to the early myth- 

 writers Achilles had been dipped by his mother 

 in the Styx, which made invulnerable every 

 part of his body except his heel, by which she 

 held him. His death-wound, made by an 

 arrow, he received in this heel. See HECTOR; 

 TROY; ILIAD. 



Tendon of Achilles. Because it was by the 

 heel that this great Greek hero was held, the 

 strong tendon which connects the muscles of 

 the calf with the heel is known as the tendon 

 of Achilles. It may be easily felt just above 

 the heel. F.J.C. 



ACID, as' id, a name applied to a number of 

 chemical compounds, having more or less the 

 qualities of vinegar. The general properties 

 assigned to them are a tart, sour taste, the 

 power of changing a vegetable blue called lit- 

 mus into red, of acting upon and dissolving 

 metals and of being rendered neutral by alka- 

 lies (see ALKALI). 



Blue litmus is made from a kind of lichen 

 which grows on the seacoasts of Europe. It 

 is supposed that the change from blue to red 

 which the litmus undergoes when treated with 

 an acid is due to a change in the relative posi- 

 tion of the atoms in one of the chemical com- 

 pounds contained in the litmus. An acid 

 always contains hydrogen, and it is always 

 possible to take the hydrogen from an acid 

 and replace it with a metal, with the result 

 that what is known chemically as a salt is 

 produced. An instance of a hydrogen com- 

 pound that is not an acid is water, which is 

 composed of hydrogen and oxygen. However, 

 when hydrogen and chlorine combine, the 

 product is an acid, hydrochloric acid; for the 

 hydrogen can be replaced by such a metal as 

 sodium, and sodium chloride is produced. The 

 latter happens to be what every child knows as 

 common salt. 



Many acids are harmless if taken internally, 

 while others, themselves compounds of ele- 

 ments that cannot do harm, are deadly poisons. 

 When we eat oranges or lemons we swallow 

 citric acid. Grapes contain tartaric acid; 

 apples, malic acid; and vinegar, acetic acid. 

 All of these are harmless, but oxalic acid and 

 carbolic acid, although made up of the same 

 elements as the others namely, carbon, hydro- 



