observes the boiling-point, then introduces also a known amount of his substance, and again observes the boiling-point. In the case of most solvents, the inner tube need not be heated directly, and heating only the outer vessel is sufficient to keep the liquid in the inner tube boiling.
What has been said above of pure boiling water applies equally well to any other compound in the liquid state; any liquid consisting of one single chemical compound has a definite boiling-point depending on nothing but the external pressure. Thus, under normal atmospheric pressure, the boiling-point of ether is 35° C.; the normal boiling-point of pure alcohol is 78°; aniline boils at 183°, and the hydrocarbon picene at 520°. The boiling-temperature is, of course, very easy to determine; and since it is one of the highly characteristic properties of a liquid, a chemist determines that point usually before inquiring into other properties when called upon to identify a liquid compound. Further, since in the case of a pure chemical compound, if the vapors are allowed to escape, the boiling-temperature remains constant, while in the case of a solution (or any other homogeneous liquid mixture), it continuously rises; whenever a chemist wants to ascertain whether he is dealing with a single and pure chemical compound, he subjects his liquid to distillation, to see whether the boiling-point will remain constant. If it does not remain constant he knows that he is dealing with a mixture or that some chemical change is taking place in the liquid.
From the fact that every compound has a characteristic boiling-point of its own, chemists were naturally led to think: (1) that some definite relation must surely exist between the chemical nature of compounds and their boiling-points, and hence (2) that in comparing compounds of similar constitution, definite numerical relations should be expected to exist between the boiling-points of such compounds. As a matter of fact, in the homologous series of organic chemistry, the boiling-point is generally found to increase with the complexity of the molecule (see, for example, the article Hydrocarbons); which shows that the boiling-point of compounds is really dependent on their nature and structure. The numerical relations hitherto discovered are, however, far from being definite and general. Probably we do not know as yet how to search for the more definite relations.
BOILLY, bwä′yē̇′, Louis Léopold (1761-1845). A French painter, born at La Bassée (Nord). He was at first a portrait painter, and began working in Paris in 1779. He won a considerable popularity as a depicter of the bourgeoisie from the reign of Louis XVI. to the close of the Restoration. He has been credited with no less than five thousand pictures, many of them Revolutionary scenes, and the best belonging to the epoch extending from the Revolution to the Consulate. In design he is firm and accurate, in color generally even. Many of his works were engraved, and he himself did creditable lithographing. His two most famous paintings are perhaps “The Arrival of the Diligence” (1803) and “Isabey's Atelier" (with portraits of twenty-four artists).
BOIS D'ARC, bwä′därk′. See Osage Orange.
BOIS DE BOULOGNE, bwä de bo͞o′lō̇′ny’. A famous and beautiful park of Paris covering about 2250 acres. It derives its name from the town of Boulogne-sur-Seine on its south. The park was formed under Napoleon I. out of the old Forêt de Rouvray, and remained in the possession of the State until transferred to the city by Napoleon III. in 1852, since which time it has been the favorite drive of Parisians. The Bois was greatly injured by bombardment during the siege of Paris in 1870'-71, but was soon restored. It contains the great Auteuil and Longchamps race-courses. With the races for the Grand Prix of Longchamps (100,000 francs), held in the early part of June, the Parisian season closes. The Bois contains also the Jardin d'Acclimatation. See Paris.
BOIS DE CHYPRE, bwä′ de shē̇′ pr’. See Elm.
BOISDEFFRE, bwä′dĕfr′, Raoul François Charles le Mouton de (1839—). A French soldier, born at Alençon (Orne). He studied at the College of Saint Cyr and at the Staff-College. During the Franco-Prussian War he was a major of cavalry and aide-de-camp of General Chanzy, and in 1882 was promoted to be colonel. In 1890 he became assistant chief-of-staff, and in 1893 chief-of-staff. At the trial of Emile Zola (1898), during the Dreyfus agitation, he appeared full-uniformed in court, and in a much-applauded address to the jury, affirmed the existence of a third secret document incriminating the accused officer. When subsequently it transpired, through the confession of Lieutenant-Colonel Henry, that the document to which he had referred in good faith was a forgery, he tendered his resignation.
BOIS DE VINCENNES, văN′sĕn′. A park of 2250 acres on the east of Paris, formerly a hunting forest of Louis IX. A large part of the park is taken up by the Champ de Manœuvres, an infantry drill-ground, a race-course, and the polygone d'artillerie.
BOISE, boi′ze. A city, the county-seat of Ada County, Idaho, and capital of the State, 400 miles northwest of Salt Lake City, Utah, on the Boise River and on the Oregon Short Line Railway (Map: Idaho, A 4). It is the centre of an agricultural and mining district, and has large stock-raising interests; it is one of the most important inland wool markets in the United States, and controls a large general trade with southern Idaho. Water derived from the Boise River is utilized for irrigation, and also for power in the manufacturing industries. Natural hot water exists here in abundance, and is extensively used in heating the buildings of the city. Among the prominent features are a natatorium, the public library, several academies and a high school, business colleges, United States assay office, United States court, United States land office, the State capitol, penitentiary, and Soldiers' Home. Boise was settled in 1863, and in 1864, with a population of 300, it was organized as a city and became the capital of the Territory. Its charter provides for a mayor, elected biennially, and a single-chambered city council. Population, in 1890, 2311; in 1900, 5957.
BOISE, boiz, James Robinson (1815-95). An American educator. He was born at Blandford, Mass., and in 1840 graduated at Brown University, where he was professor of Greek from 1843-50. From 1852 to 1868 he was professor of Greek language and literature at the University
