Page:The American Cyclopædia (1879) Volume IX.djvu/138

 130 HYDROSULPHURIC ACID HYGIENE HYDROSULPHURIC ACID, Solphydrle Aeid, or Sulphuretted Hydrogen, a gaseous compound first examined by Scheele in 1777; symbol, H 2 S; chemical equivalent, 34. It consists of two volumes of hydrogen and one of sulphur vapor condensed into two volumes, which form its combining measure. Its density is 1191-2, air being 1000. It is a colorless gas, has a slight acid reaction, and a most offensive odor, rec- ognized in rotten eggs, dock mud, cesspools, many mineral waters, and putrefying organic ' matters containing sulphur. It extinguishes flame, but burns itself in contact with air with a blue flame, depositing sulphur. It is condensed by a pressure of 17 atmospheres at 80 into a colorless liquid, and was solidified by Faraday by cooling to 122 into a white crystalline translucent substance. Water ab- sorbs 2 times its volume of the gas ; alcohol 6 volumes. It blackens the salts of lead and of many other metals, forming sulphides of the metals. These being insoluble and made readily visible by their peculiar colors, even in minute quantity, the acid is a convenient test for determining the presence of the metals in solutions, and distinguishing them by the color of the precipitate and its other properties. Its aqueous solution and its solution in ammonia (hydrosulphide of ammonium) are among the useful chemical reagents. The gas is exceed- ingly noxious to inhale. Thenard found that a small bird would die in air containing ;-$-$ part of it, and a horse in air that contained yj-j of it. The gas is neutralized and de- composed by chlorine and iodine, which unite with its hydrogen ; and the former, furnished by chloride of lime wet with strong vinegar, is a convenient antidote and disinfectant of the gas. Nitrate of lead, chloride of zinc, sulphate of iron, and sulphate of manganese are also efficacious in this respect. The presence of the gas is detected by its odor, and by its black- ening a paper wet with a solution of acetate of lead. It is the cause of the discoloration of white lead paint in the apartments of houses, also of the blackening of silver spoons when these are used with boiled eggs, the albumen of the white of the egg furnishing the sulphur for the production of the gas. To prepare hydrosulphuric acid, the ingredients employed are a ferrous sulphide, made by exposing to a low red heat 4 parts of coarse sulphur and 7 of iron filings, and diluted sulphuric acid. By pouring the acid upon broken lumps of the compound in a gas bottle, the gas is evolved, and may be collected in a bell glass over water at 80 or 90, or over brine. It is absorbed by cold water. It may also be obtained by the action of hydrochloric acid upon antimo- nious sulphide. The reactions in each case are thus expressed : FeS + H a SO, = FeSO + H 2 8. Sb 2 S 3 + (HOI), = (SbCl,), + (11,8),. HYDBCIVTUM. See OTRANTO. HYEBES, a town of France, in the depart- ment of Var, on the S. declivity of a hill, 9 m. E. of Toulon, and 3 m. from the Mediterranean : pop. in 1866, 10,878. The principal edifices are the old church, one of the most singular structures in France, and an ancient chateau, now used as a town hall. In the principal square is a column, surmounted by a white marble bust of the celebrated Massillon, who was a native of the town. Hyeres is consid- ered one of the healthiest winter residences in the south of France, and is much resorted to by invalids. Remains of an ancient Roman city exist in its vicinity. In the roadstead op- posite the town, and belonging to it, is a group of small islands called the isles of Hyeres (an- cient Stcechades), two of which are fortified. During the middle ages the place was called Hiedera, and was a favorite port of the pilgrims to Jerusalem. HYGIEA, or Hygea, in Greek mythology, the goddess of health, a daughter of ./Esculapius. She was represented by artists as a virgin in flowing garments feeding a serpent from a cup ; the poets speak of her as a smiling goddess with bright glances, and a favorite of Apollo. By the Romans she was in time identified with the old Sabine goddess Sains. HYGIENE (Gr. v-yteivdf, healthy), the science and art of preserving health, by the appro- priate nourishment of the body and the proper regulation of its surrounding conditions. The first subject of importance in a hygienic point of view is always the location or residence of the individual, family, or community whose interests are involved. Other conditions may be altered or modified with comparative readi- ness, but the place and character of the habi- tation, when once fixed, usually remain so for a considerable time, and thus exert a con- tinued influence for good or evil. The habi- tation, when in the country, should always be placed upon such an elevation as to secure a thorough natural drainage. This is the first requisite; for there is no other single cause of disease so hurtful and insidious as the slow ac- cumulation and stagnation of the refuse mat- ters, in however small quantity, which are daily produced in and about an occupied habi- tation. Even standing pools, or hollow basins without an outlet, the result of a depression in the surface of the ground, should not be allowed in the immediate neighborhood of the house ; for although it is only the rain water which at first collects in them, yet there is always more or less accumulation of organic matter from vegetable growth and from the aquatic animals and birds which make such places their resort ; and as a pool of this kind is alternately filled and dried up, sometimes several times a year, the effluvia exhaled during this process will always become more or less injurious, and may be even dangerous to life. When a large number of inhabitants are col- lected within a small space, as in towns and cities, the question of drainage becomes of course still more important. The production of refuse inaterials is here exceedingly rapid, and corresponding provision should be made