152 ANTOZONE OXIDIZES WATER. 181. Besides its power of forming clouds or mists with water, which is interesting rather as a physical than as a chemical fact, antozone, particularly when newly formed, also unites with water chemically, the substance called peroxide of hydrogen (see § 61), whose composition is expressed by the formula H,O,, being the result of the combination. A simple method of exhibiting the formation of peroxide of hydrogen by the action of antozone upon water, is to place a short, narrow tube, containing concentrated sulphuric acid, within a bottle 2 or 3 c.m. in width, furnished with a ground-glass stopper, and filled with water nearly to the top of the tube. Small portions of peroxide of barium are now added, at intervals, to the sulphuric acid in the tube, elevation of temperature being avoided as far as possible; the stopper should be replaced in the bottle after each addition of the peroxide. Most of the oxygen evolved in this process appears, however, to be in the ordinary inactive state, and the solution of peroxide of hydrogen obtained is consequently extremely dilute. A better method of procedure is to pass a current of carbonic acid gas into a mixture of water and peroxide of barium, BaO, + H,O + CO, = BaO,CO. +H,O.. In this way a highly concentrated solution of the peroxide can be obtained. Another easy method of preparing peroxide of hydrogen is by the oxidation of amalgams of lead or zinc. In this case also, as in the preceding, the peroxide of hydrogen is probably formed by the union of antozone with water. One hundred grammes of lead-amalgam, containing so much mercury that it shall be fluid at the ordinary temperature, is shaken in a bottle of the capacity of a litre, together with 200 c. c. of water, acidulated with 2 grms. of sulphuric acid; the water soon becomes milky from separation of sulphate of lead, and in the course of ten or twelve minutes contains enough peroxide of hydrogen to exhibit the characteristic reactions of this substance. So, too, if pulverulent zinc-amalgam be loosely thrown into a glass funnel, with narrow throat, and a thin stream of water be allowed to flow through it in such manner that the metal may be at the same time acted upon by both air and water, the water will become charged with peroxide of hydrogen. By repeatedly pouring back the dilute solution of the peroxide upon the amalgam, it can be very considerably strengthened. In order to prepare the zinc-amalgam, equal weights of zinc-filings and of mercury are placed in a beaker glass, covered with DIFFERENCES BETWEEN OZONE AND ANTOZONE. 153 water acidulated with sulphuric or chlorhydric acid, and thoroughly mixed by stirring with a glass rod; the acid is then poured away, and the last portions of it removed from the amalgam by washing with water. This power of antozone to oxidize water distinguishes it completely from ozone, which has little or no action upon water. 182. Peroxide of hydrogen, like peroxide of barium, is supposed to contain one atom of oxygen in the form of antozone; the peroxides of potassium, sodium, and strontium also are placed in the same category. They are all called antozonides. 183. Antozone can be distinguished from ozone by the following tests: Strips of paper, charged with a solution of sulphate of manganese (Exp. 77), do not become brown when exposed to the action of antozone; on the contrary, manganese papers which have been browned by ozone are bleached by antozone. Guaiacum paper (Exp. 78) does not become blue in antozonized air. The yellow compound called ferrocyanide of potassium, which is converted into red ferricyanide of potassium by the action of ozone, is not changed by antozone. In the absence of acids, antozone has no action upon iodide of potassium. The chemical behavior of antozone may be conveniently studied by resorting to its compound with water, the antozonide peroxide of hydrogen. If peroxide of hydrogen be brought in contact with an ozonide like peroxide of lead, for example, both of the peroxides will be reduced, and there will result water, protoxide of lead, and free ordinary oxygen. Whenever an antozonide is mixed with an ozonide, a similar reaction occurs; the two active varieties of oxygen disappear, and common oxygen is evolved; hence it has been assumed that ordinary inactive oxygen is a sort of compound, resulting from the union or neutralization of ozone with antozone. Several important tests for antozone are dependent upon this fact of the decomposition of antozonides by ozonides. If a liquid suspected to contain peroxide of hydrogen be shaken in a test-tube with a small quantity of ether, the ether will dissolve the peroxide, and will finally collect upon the surface of the liquid; on adding to it a small drop of a solution of the ozonide chromic acid, or, what comes to the same thing, a drop of a solution of bichromate of potassium acidulated with sulphuric acid, the ethereal solution will become blue. If a liquid containing peroxide of hydrogen be added to a dilute red solution of permanganate of potassium, this solution will be decolorized, while common oxygen will be evolved; and in the same way the brown peroxide of lead and the red-colored salts of peroxide of iron are bleached by it. Another exceedingly delicate and characteristic test for antozone, or rather for peroxide of hydrogen, the rationale of which has not yet been well made out, is the following:-If to a solution containing peroxide of hydrogen there are added a few drops of dilute starch-paste charged with iodide of potassium, and subsequently a very small quantity of a solution of copperas (protosulphate of iron), iodine will be set free, and the starch will become blue. The solution to be tested must be as nearly neutral as possible. The addition of an acid, instead of the copperas solution, will also bring about the same reaction, though less readily. 184. We have thus set forth whatever is best known concerning ozone and antozone, in spite of the details into which so full an exposition has necessarily descended, partly because the subject will evidently be one of primary importance, both theoretical and practical, in the near future, and partly from a desire to show the student how vague and uncertain the prospect is when once the narrow limits of established knowledge are past and the inquirer ventures out into the obscurity which perpetually separates the knowledge of to-day from that which shall be knowledge to-morrow, but also because of the impossibility, with so obscure a subject, of making such a just discrimination between salient and unimportant points as with a well-studied subject is both easy and desirable. CHAPTER XIII. SULPHUR. 185. Sulphur occurs somewhat abundantly in nature, both in the free state and in combination with other elements. Many ores of metals, for example, are sulphur compounds. It is a component of several abundant salts, such as the sulphates of calcium, barium, and sodium, and occurs in small proportion in THE SULPHUR OF COMMERCE. 155 many animal and vegetable substances. Free sulphur is found chiefly in volcanic districts. Generally it occurs mixed with earthy matters; but it often forms distinct veins, and is sometimes found in the shape of well-defined crystals of considerable size. At the present time about nine-tenths of the sulphur of commerce comes from Sicily. 186. Native sulphur is usually subjected to a rough purification at the place of its occurrence. This purification is sometimes effected by distilling the volcanic earth in retorts or jars of earthenware; the sulphur being volatile, distils over, and is collected in receivers, from which it is drawn off, from time to time, in the liquid state; or if the earth be very rich in sulphur, it is simply heated in large kettles and the melted sulphur dipped off from above, while the earthy impurities settle to the bottom of the kettle. The product thus obtained is known as crude sulphur; it comes to us in irregular lumps of a dirty light-yellow color, and is largely employed for manufacturing-purposes. This crude sulphur is contaminated with more or less earthy matter. In order to purify it, it is distilled from iron retorts into large chambers constructed of masonry, in which it is deposited either in the form of a light powder, known as flowers of sulphur, or in a liquid state, according to circumstances. At the beginning of the operation, while the chamber is cold, the sulphur vapor condenses as an exceedingly fine, soft, powder (flowers of sulphur) upon the walls of the chamber. But heat is given off as the sulphur vapor condenses, and after a while the walls of the chamber become so hot that sulphur will melt upon them. After this, the incoming sulphur vapor of course condenses only to the liquid state, and a layer of liquid sulphur collects upon the floor of the chamber. This liquid sulphur is drawn off into wooden moulds, and thus cast into the sticks familiarly known as roll-brimstone. It is evident that, by a little management, the sulphur-refiner can obtain, at will, either flowers of sulphur or roll-brimstone, or first the one and then the other. 187. At the ordinary temperature of the air, sulphur is a brittle solid, of a peculiar light-yellow color. It has neither taste nor smell, excepting that when rubbed it exhales a faint and peculiar odor. Most of the odors which in everyday life are 156 CRYSTALLIZATION OF SULPHUR. referred to sulphur are really the odors of various compounds of sulphur, and are not evolved by the element itself. It is a bad conductor of heat and electricity. On being rubbed it becomes highly (negatively) electric, and is still employed as a source of electricity in some cases. The symbol of sulphur is S; its atomic weight is 32, being precisely twice as great as the atomic weight of oxygen. 188. Sulphur melts easily at about 112°, a temperature not very far above that at which water boils. A fragment of it may even be melted by heating it on writing-paper over the flame of a candle. It volatilizes freely at temperatures lower than its melting-point, and boils at 440°. Indeed, as is the case with water, it is a substance which can be brought into either of the three states of matter without any difficulty; we can have it as a solid, a liquid, or a gas as we please. It can readily be obtained also in the form of crystals. Erp. 79. In a small beaker glass, or porcelain capsule, heat slowly 50 to 60 grms. of sulphur until it has entirely melted. Remove the vessel from the lamp, and allow it to cool slowly until about a quarter part of the sulphur has solidified; then pour off, into a basin of water, that portion of the sulphur which is still liquid, breaking through, for this purpose, the crust at the top of the liquid, if any such have formed. The interior of the vessel will be found to be lined with transparent, prismatic crystals. Exp. 80.-In a test-tube, melt enough sulphur to fill one-quarter of the tube; place the tube in such a position that its contents may cool slowly and quietly, and then watch the formation of crystals as they shoot out from the comparatively cold walls of the tube towards the centre of the liquid. Exp. 79 represents one general method of obtaining crystals. Crystals of many of the metals, lead and bismuth for example, can be obtained by operating in this way; it is only necessary to melt the metal in a crucible of some refractory material, placed in a furnace. The melted metal having then been allowed to cool until a tolerably firm crust has formed upon its surface, this crust is pierced with an iron rod, and the crucible quickly inverted, so that the portion of the metal which still remains fluid in the interior shall flow out. Upon afterwards breaking |