202. Describe the experiment which illustrates the bleaching property of burning sulphur ? 203. Why does sulphur, when thrown on a fire, extinguish it? 204. Has it any effect on sour wine? 205. What is meant by sulphur seals? 44509 SULPHURETTED HYDROGEN. 54. When sulphur unites with hydrogen in the proportion of one hyd. to sixteen sulph., sulphuretted hydrogen is formed. This gas, which has an extremely offensive odour, similar to a decomposed egg, which contains this gas, is nearly twice as heavy as our atmosphere, and is extremely destructive to animal life when breathed. These two properties render it a useful agent for destroying rats: this is accomplished by pouring the gas into their holes. It is combustible, and burns with a pale blue flame. When ignited in a close glass jar, there is a deposition of sulphur on the sides of the vessel. It is decomposed by our atmosphere, the oxygen of which unites with its hydrogen to form water, the sulphur being left behind. This is the origin of the sulphur which is found near mineral springs. The disagreeable smell which arises from drains arises partly from the presence of the same gas. Though so unpleasant, it possesses important medicinal properties. This is the case with the waters of Harrowgate, Aix-la-Chapelle, and Lucan, near Dublin. These are termed sulphurous spas. 55. Sulphur heated with potash (composed of potassium and oxygen) unites with the potassium, which is here called a base, and forms sulphuret of potassium. In this way sulphur may be combined artificially with most of the metals (vide exper. 48); but many of the metallic sulphurets are found in abundance, native (naturally formed). Experiment 50.-If we pour some muriatic acid and water, termed diluted, on sulphuret of iron, the following change takes place :-The water is decomposed (vide exper. 28); its hydrogen unites with the sulphur to form sulphuretted hydrogen, which passes off as a gas. The oxygen seizes the iron, forming oxide, which unites with the muriatic acid. In this way the gas can be prepared for experiment. As this gas is rapidly absorbed by cold water, it is advisable, when collecting it in the pneumatic trough, to use warm water. 56. Gold and silver, though not affected by being exposed to oxygen-hence called non-oxidizable metals are tarnished by the sulphuretted hydrogen which is generally mixed with our atmosphere. It is this combination that renders plate-powder necessary. PHOSPHORUS. 58. This peculiar element is chiefly of animal origin. Its name is derived from the Greek pws, light, and pepw, to carry, as it emits light which is visible in the dark. It was accidentally discovered in 1677, by Brandt, an alchemist of Hamburg. In 1774, the celebrated chemist Scheele, of Sweden, ascertained that it could be obtained from the bones of the higher animals. From this source it is procured in the present day, by the following process (which is, perhaps, a little too difficult for a very young pupil):-Bones (which are principally composed of gelatin, (animal jelly,) lime, and phosphoric acid, i.e. oxygen and phosphorus) are burned till they become white; they are then ground to fine powder. When exposed to fire, bones lose their gelatin, and the white mass principally consists of phosphoric acid and lime, as above; the compound is termed phosphate of lime. To obtain phosphorus from the powder, three parts are mixed with two of vitriol, and thirty of water. The vitriol, having a superior attraction or affinity for lime, takes a portion of it from the phosphate of lime, forming sulphate of lime, which is precipitated, i. e. falls to the bottom of the vessel. The remaining portion of lime in the solution unites with all the phosphoric acid, forming a salt, which is soluble in the liquid. When this is strained, the sulphate of lime is left behind. The strained liquor is then evaporated, i.e. boiled down till it becomes as |