ESTERS 60 ETCHING ESTERS, ethereal salts formed by the reaction between an acid and an alcohol. For instance C2H.OH 4- HCl Alcohol Hydrochloric Acid C^H.Cl + H.O Ethyl Chloride Water Ethyl Chloride is the hydrochloric acid ester of ethyl alcohol. The change from an alcohol to an ester is never complete, because the reaction is reversible; that is to say, esters are decomposed by water, giving acid and alcohol. When an alcohol and an acid are mixed, there- fore, the reaction illustrated above pro- ceeds to a certain point until a balance, or equilibrium, is reached, the final prod- uct being a mixture of alcohol, acid, ester, and water. If, however, the water produced is removed, and so prevented from decomposing the ester, the reaction is far more nearly complete, and it is a common practice to employ, a dehydrat- ing agent, such as sulphuric acid, which combines with the water as fast as it is formed. Esters are usually pleasant-smelling, colorless liquids, and the odor of flowers and fruits is frequently due to their presence. Many artificial flavorings, es- sences, and perfumes consist of esters. Some of the best known are methyl salicylate (oil of winter green) amyl acetate (banana or pear oil) methyl butyrate (pineapple oil) and isoamyl isovalerate (apple oil). ESTHER (es'ter), a Jewess who be- came the queen of Ahasuerus, King of Persia, and whose story is told in the book of the Old Testament called by her name. This book is supposed by some to be the composition of Mordecai him- self, the uncle of the heroine. The feast of Purim, which commemorates the events narrated, is still observed by the Jews during the month Adar. ESTHONIA, a former maritime gov- ernment of Russia, bounded by the Gulf of Finland, the Baltic and the former governments of Livonia and Petrograd. It includes sevei'al islands, of which the most important are Dagoe and Oesel ; area, 23,160 square miles. It has for the most part a flat or undulating surface. The whole of the N. side, how- ever, rises considerably above the sea, and presents to it ranges of cliff's. The Narva, which merely bounds Esthonia on the E., is the only river of any im- portance; but minor streams, as well as small lakes, are very numerous. About a fourth of the surface is covered with forests of pine, birch, and alder. The crops include a little wheat, much barley and oats, and some flax, hops, and tobac- co. Cattle are reared, and active fish- eries are carried on. The peasantry are almost all of Finnish origin, and speak a Finnish dialect. In the 10th and 12th centuries it belonged to Denmark; it was afterward annexed by Sweden, and in 1710 was seized by Russia. Reval is the capital. Pop. (1919) 1,744,000. On Feb. 24, 1918, the National Council of Esthonia declared for an independent state, which was recognized de facto by Great Brit- ain. After the conclusion of the World War (1914-1918) the government of Es- thonia was established. ESTRADA, a town of Spain, in the province of Pontevedra. It is on the Rio Ulla. It is the center of an exten- sive farming and stock-raising region, and has manufactures of woolen and linen goods. Pop. about 30,000. ESTRADA CABRERA, MANUEL, a president of Guatemala, born in Guate- mala in 1857. He studied law and be- came a justice of the Supreme Court. In 1892 he was appointed Secretary of State. He became acting president in 1898, following the assassination of Pres- ident Barrios, and was successively re- elected, becoming actual dictator of the country. He did much in improving con- ditions in Guatemala, especially along agricultural and industrial lines. He was compelled to abdicate the presi- dency in 1920. ESTREMADURA (es-tra-ma-do'ra), a W. division of Spaiu, consisting of the provinces of Badajoz and Caceres. It is fertile, but not cultivated to its full ex- tent. The Tagus and Guadiana inter- sect it E. to W. Immense flocks of sheep graze on the rich plains. The area is about 16,100 square miles. Pop. 882,000. ESTREMADURA, a maritime prov- ince of Portugal, divided by the Tagus into two nearly equal parts, of which the N. is the more mountainous. Wines and olives are the principal produce. The principal city is Lisbon. Area, 6,937 square miles. Pop. about 1,250,000. ESTUARY, the wide mouth of a river opening out so as to form an arm of the sea. ETAWAH (e-ta'wa), a town in Hin- dustan, Northwest provinces; capital of the district of the same name on the left bank of the Jumna, picturesquely situ- ated among ravines, and richly planted with trees. It has some good buildings and a considerable trade. ETCHING, the art of producing de- signs on a plate of steel or copper by means of lines drawn with an etching needle. See Engraving.
