Complete Text (Part 19)

on the com- bustion of magnesium ? 20. How much antimonous oxide can be produced by roasting one kilogram of antimonous sulphide ? 21. What is the algebraic combining number of the oxygen in water and what is it in "hydrogen dioxide" ? 22. Is hydrogen dioxide really an oxide, or can you give a more scientific name for it? 23. What is the importance of hydrogen oxide to plants and animals? AIE AND WATEE— NITROGEN, OXYGEN AND HYDROGEN 191 24. What is meant by ionization ? 25. How is hydrogen produced ? 26. What products are formed when steam is passed over strongly heated coal ? 27. Name four great classes of compounds containing hydrogen. 28. If you remove one hydrogen atom from each of two molecules of water and put one atom of sulphur in their place, what will be the compound formed ? 29. If you put one atom of sulphur in the place of four hydrogen atoms removed from four molecules of water, what will be the resulting compound ? 30. If you put a nitrogen atom in the place of five hydrogen atoms removed from five molecules of water, what will be the resulting compound? 31. If you put a sodium atom in the place of one hydrogen atom of a molecule of water, what will you have ? 32. If you put a calcium atom in the place of two atoms of hydrogen removed from two molecules of water, what will be formed ? 33. If you put one sulphur atom in the place of six hydrogen atoms taken from six molecules of water, what will be the compound formed ? 34. If from that compound you remove two hydrogen atoms and one oxygen atom, what will remain ? 35. If you remove from it four hydrogen atoms and two oxygen atoms, what will be the technical name of the residue ? 36. If you take away three molecules of water from the compound formed by putting one sulphur atom in the place of six hydrogen atoms removed from six molecules of water, what will be left ? 37. Why are acids, bases and salts said to be built on the water type ? 192 A CORRESPONDENCE COURSE IN PHARMACY 38. In what way may the highest temperature be produced that can be obtained by chemical means ? 39. What is the composition of hydrogen telluride ? 40. Write the molecular formulas of hydrogen bromide, hydrogen nitride, hydrogen phosphide, hydrogen silicide, hydrogen carbide and hydrogen boride. 41. If the atomic weight of oxygen be set down as 100, what will be the corresponding atomic weight of hydrogen ? 42. Explain why an element is said to be reduced whenever it enters into combination with hydrogen, but oxidized whenever it enters into combination with oxygen. LESSON FOURTEEN XX Fluorine, Chlorine, Bromine and Iodine 291. The four elements called respectively fluorine, chlorine, bromine and iodine form a natural group or family of elements closely resembling one another in their chemical properties and behavior. 292. One atom of either of these elements can hold in combination but one atom of hydrogen. The only possible hydrogen compounds of fluorine, chlorine, bromine and iodine are accordingly HF, HC1, HBr and HI. These four compounds are commonly called "acids," because they resemble the real acids in their power to neutralize alkalies; but they should instead be called the hydrogen halides, for they are binary compounds of the halogens, whereas all true acids contain more than two elements. The halides of hydrogen are often called the "hydrogen acids" or "hydracids," because they contain hydrogen without any oxygen, but as all acids contain hydrogen, the term "hydro- gen acids" is ill chosen, since its employment to distinguish between these compounds and the true acids rests not upon what they contain (H) but upon what they do not contain (0). The scientific names of HF, HOI, HBr and HI are hydro- gen fluoride, hydrogen chloride, hydrogen bromide and hydrogen iodide. 293. All binary compounds of fluorine are fluorides; all 193 194 A CORRESPONDENCE COURSE IN PHARMACY * binary compounds of chlorine except its compounds with fluorine or with oxygen are chlorides ; all binary compounds of bromine are bromides, except its compounds with chlorine or fluorine (and its' compounds with oxygen, did such com- pounds exist) ; and all binary compounds of iodine are iodides, except its compounds with bromine, chlorine, fluorine or oxygen. 294. A molecule of any fluoride, chloride, bromide or iodide may contain from one to six atoms of fluorine, chlorine, bromine or iodine, but never contains more than one atom of the positive element. A compound of fluorine and chlorine cannot contain more than one chlorine atom, but may contain one or more fluorine atoms. A chloride of bromine or iodine may contain one or three or five atoms of chlorine or bromine, but it cannot contain more than one iodine atom. This is because the combining value of any negative element in any true binary compound is unchange- able; the atomic combining value of the halogen in any halide is 1, and any member of the chlorine family of ele- ments (the fluorine, chlorine, bromine and iodine are together called the " chlorine family") having a lower atomic weight is negative in its chemical relation to any other element of the same family having a higher atomic weight. The atomic weight of F is 19, that of 01 is 35.5, that of Br is 80 and that of I is 126.5. 295. Halogens. Fluorine, chlorine, bromine and iodine are called "halogens" (from hals, salt, and gennao, I generate), because their water-soluble binary compounds with the metals look like the water-soluble true salts (formed by true acids). But some metallic sulphides and many other compounds look like salts without being such. Common table salt is the chloride of sodium. But positive chlorine, bromine or iodine cannot be called a halogen. FLUORINE, CHLORINE, BROMINE AND IODINE 195 296. Halides are the binary compounds formed by the metals and by hydrogen with the halogens. Sodium chloride is therefore a halide (from hals, salt, and eidos, like). 297. Fluorine is a greenish-yellow gas. But very little is known concerning fluorine in its uncombined state, because the intensity of its chemical energy is so great that when it is set free from any one compound it cannot be prevented from entering at once into the formation of other compounds. This element occurs in nature in the form of calcium fluoride or fluorspar, CaF2, and as cryolite, which is a so-called "double fluoride" of aluminum and sodium. Its most interesting compound is the hydrogen fluoride, commonly called "hydrofluoric acid," which is a colorless, fuming, highly corrosive liquid, very poisonous because of its destructive chemical action. It attacks glass and is used to produce etchings on glassware. 298. Chlorine is a yellowish-green gas of suffocating, char- acteristic odor, poisonous when inhaled. At 15° C. it can be compressed into a liquid under the pressure of four atmospheres. One cubic-decimeter of chlorine at 0° 0., bar. 760 mm., weighs about 3.17 grams. One volume of water at 15° C. dissolves about 2-J- volumes of chlorine. A water-solution saturated at 10° C. contains about 0.6 per cent of CI. Such a solution is called "chlorine water. " 299. Chlorine occurs most abundantly in the form of sodium chloride, or common salt, in sea-water and salt- springs, and in salt-beds or salt-mines as rock-salt. 300. Free chlorine is commonly prepared by heating man- ganese dioxide, Mn02> with hydrogen chloride, HC1 : Mn02+4HCl=MnCl2+2H20+2Cl. 301. Chemical Properties. Chlorine displays great chemical energy, which fact is usually expressed by the statement that 196 A CORRESPONDENCE COURSE IN PHARMACY it strongly attacks many other substances or has a destructive effect upon them. It unites with any one of all the other known elements (except those that form no compounds whatever, as is apparently the case with neon, argon, krypton and xenon). It displaces bromine and iodine from bromides and iodides. No one atom of any other element can unite with more than six atoms of chlorine. Noxious effluvia and other poisonous decomposition prod- ucts of organic matter are frequently unstable hydrogen compounds, and they may generally be destroyed by chlorine, because of the great affinity of chlorine for hydrogen. This explains the great disinfectant power of chlorine. 302. Hydrogen chloride, HC1, is commonly called "hydro- chloric acid." Being very unstable or easily decomposed when brought in contact with certain metals and other sub- stances, it is described as highly corrosive or destructive. Iron, zinc, aluminum and several other metals readily attack hydrogen chloride, from which they appropriate to them- selves the chlorine, thus liberating the hydrogen : Zn+2HCl=ZnCl2+2H. 303. Aqua regia is a mixture made of hydrogen chloride and nitric acid, and contains free CI together with nitrosyl chloride, ONC1. This so-called "nitrohydrochloric acid" dissolves gold and platinum, forming the chlorides of these metals. 304. Chlorides are the compounds of negative chlorine with any other elements or with certain positive compound radicals. Among the most common chlorides are : Hydro- gen chloride, HC1; sodium chloride, NaCI; ammonium chloride or "sal ammoniac" or "muriate of ammonia,' ' H4XC1; ferric chloride, FeCl3; calomel, HgCl; and corrosive sublimate, Hg012. FLUORINE, CHLORINE, BROMINE AND IODINE 197 305. Bromine is a dark-brownish-red, mobile, heavy liquid, which gives off suffocating yellowish-red vapors, intensely irritating to the eyes and the respiratory organs and extremely dangerous when inhaled. Its destructive action on organic substances, including clothing, wood, etc., render it imperative that bromine should be handled only with great caution. Bromine occurs in sea-water and in salt-springs chiefly in the form of magnesium bromide, MgBr2, from which the bromine is liberated by chlorine and in other ways. Bromine exhibits intense chemical energy. Potassium bromide, KBr, is the most common bromine compound. Hydrogen bromide is commonly called hydro- bromic acid. The binary compounds of the metals with bromine are called bromides. 306. Iodine consists of dry, brittle, purplish-black, rhombic crystal plates, having a shining appearance resembling metallic luster, a strong, characteristic, somewhat saffron- like odor, and an acrid taste. The specific weight of iodine is 4.948 at 17° C. It melts at about 114° C. and boils at 200°. Its vapor is of a beauti- ful violet or purple color. It is nearly insoluble in water but soluble in alcohol. Iodine occurs together with chlorine and iodine in sea- salts and salt-springs. It also occurs in the form of sodium iodate in the residuary liquors obtained in separating sodium nitrate from the saltpetre deposits of Chili. From sodium iodide leached out of the ashes of seaweeds the iodine is obtained in the same manner as chlorine and bromine may be liberated from chlorides and bro- mides : 2NaI+Mn02+2H2S04=MnS04-f^"a2S04+H20+2I. The most common iodide is that of potassium, KI. 198 A CORRESPONDENCE COURSE IN PHARMACY XXI Sulphur, Selenium and Tellurium, Phosphorus, Arsenic and Antimony, Carbon and Silicon, Boron 307. Sulphur is at ordinary temperatures a light yellow, hard, odorless and tasteless solid. Its specific weight varies from 1.96 to 2.07. It melts at about 114° C. to an amber- colored liquid. When carefully fused sulphur is allowed to cool slowly it crystallizes, and if the still liquid portion be poured off before the whole mass solidifies long crystals can be obtained. Molten sulphur heated beyond 150° 0. darkens and thickens, and at nearly 200° it becomes almost black and so tough that it scarcely runs. Heated higher it gets thinner again, and if then poured into water and allowed to cool it forms a soft, tough, yellowish-brown solid. Sulphur boils at 446° C. Brimstone is impure sulphur molded into cylindrical sticks. Sublimed sulphur ', or "flowers of sulphur," is a light yellow crystalline powder. Precipitated sulphur is an extremely fine, pale, greenish- yellow powder, without odor and taste. When sulphur is ignited it burns with a blue flame, forming sulphur dioxide, S02, which may be at once recognized by its pungent "sulphurous" odor and irritating effects upon the respiratory organs. Sulphur is insoluble in water and in alcohol, but readily soluble in benzin, benzol, oil of turpentine and several other oils, and in ether and chloroform. 308. Occurrence in Nature. Sulphur is found in immense quantities in Italy, South America, California, Louisiana and elsewhere. In combination with iron, copper, lead and zinc it occurs in great abundance. "Iron pyrites" is FeS2; " copper SULPHUE, PHOSPHOKUS, ARSENIC, ANTIMONY, ETC. 199 pyrites" is CuFeS2; "galena" is PbS; and "zinc blende" is ZnS. 309. Chemical Properties. Sulphur does not exhibit any- great inclination to form compounds with other elements except at high temperatures. Negative sulphur forms compounds whose structure is exactly analogous to that of the compounds of oxygen. These sulphur compounds are called sulphides when they correspond to the oxides; they are called "thio-salts" when analogous to oxygen salts. Positive sulphur is sulphur in direct combination with either oxygen or with one of the four halogens (fluorine, chlorine, bromine or iodine). One sulphur atom can hold in combination either two or three oxygen atoms, forming the two oxides, S02 and S03. S02 forms sulphurous acid with water ; S03 forms sulphuric acid. 310. Selenium and tellurium are rare elements which form compounds exactly analogous to those formed by sulphur. ,311. Phosphorus occurs chiefly in the form of a soft white, or slightly yellowish, semi-translucent solid of a peculiar odor and taste. It emits white fumes when exposed to the air and on longer exposure it ignites spontaneously and burns with a fierce flame, forming phosphoric oxide, P205, which is a snow-white solid. Owing to the intense inflam- mability of phosphorus it must be kept under water in strong glass-stoppered bottles in a cool, secure place. It is very poisonous. Phosphorus is insoluble in water, but soluble in 350 parts of absolute alcohol at 15° C, in 80 parts of absolute ether, in about 50 parts of any fixed oil, and very freely in chloro- form and carbon disulphide. When the ordinary or waxy phosphorus is heated in a closed vessel to about 300° C. it is converted into red phosphorus, 200 A CORRESPONDENCE COURSE IN PHARMACY which is an amorphous dark-red powder, not poisonous nor self-inflammable. 312. Phosphorus occurs principally in the form of calcium phosphate in bones, and in the mineral called apatite. It is made from " bone-ash" or " calcined bone," which consists chiefly of calcium phosphate. 313. Arsenic is an element occurring chiefly in the form of sulphides. The so-called "cobaltum" of commerce is not cobalt but an impure arsenic. Arsenic is a dark steel-gray, brittle solid of a somewhat metallic luster. It is not a metal, because it combines directly with hydrogen to form H3As, and it does not per- form the basic function, so that oxygen salts with arsenic as the basic element do not exist. Chemically this element is closely related to nitrogen, phosphorus and antimony. 314. Compounds of arsenic are poisonous. Their structure is illustrated in the following examples : As203 is arsenous oxide, commonly misnamed "arsenous acid." H2HAs03 is arsenous acid. K2HAs03 is potassium arsenite, contained in the medicinal preparation called "Fowler's Solution." Na2H As04 + 7H20 is crystallized sodium arsenate. Na4As207 is sodium pyroarsenate. 315. Antimony occurs in nature chiefly as antimonous sulphide, called antimonite. This element looks decidedly like a metal, having a high metallic luster. It is also very heavy, its specific weight being 6.8. But it combines with hydrogen to form H3Sb, and it performs the basic function but feebly if at all. The only water-soluble antimony compound is "tartar emetic," which has the composition 20SbKC4H406 -f H20. Sb2S3 is antimonous sulphide. The "black sulphide of SULPHUR, PHOSPHORUS, ARSENIC, ANTIMONY, ETC. 201 antimony" is crystallized antimonous sulphide. Precipitated antimonous sulphide is yellowish-red. Sb203 is antimonous oxide. Sb2S5 is antimonic sulphide. SbCl3 is antimonous chloride. 316. Carbon is an element common to all vegetable and animal substances. In its free state it exists in several forms, viz. : diamond, graphite, soft coal, hard coal and peat. Coke, wood charcoal, animal charcoal and lampblack are also carbon. Combined carbon is contained not only in all vegetable and animal substances but also in limestone, chalk, marble, magnesite, etc. In its ordinary forms carbon is a solid, inodorous, tasteless substance, insoluble in all liquids, infusible and non-volatile. When heated strongly in the air it ignites and burns, form- ing C02 if the supply of air or oxygen is abundant, but CO if the supply is deficient. 317. The chemical properties of carbon are extraordinary. At common temperatures it shows no chemical energy ; but at a high heat it readily combines with oxygen, forming either C02 or CO, according to whether the supply of oxygen is liberal or deficient. It, therefore, has two combining values, 4 and 2. But the valence of the carbon atom in nearly all known carbon compounds is 4. The most remark- able characteristics of carbon are that its atoms can hold each other in combination to form chains or rings which give character to innumerable organic substances, and that the same carbon atom can hold in combination with itself both positive and negative elements at the same time. Thus hydrogen, which is positive, and oxygen, which is negative, can both be held in combination with the same carbon atom, as in H3COH. 318. The compounds formed by carbon with hydrogen 202 A CORRESPONDENCE COURSE IN PHARMACY alone are called hydrocarbons. The simplest of these is H4C, because it contains but one carbon atom. Hydrocarbons containing a small number of carbon atoms are gases ; others, with a larger proportion of carbon, are liquid; and those containing much carbon are solids. Coal oil is a mixture of hydrocarbons. Benzin, gasolin, petrolatum, paraffin, naphthaline, terebene and benzol are all hydrocarbons. Nearly all volatile oils contain one or more kinds of hydrocarbons. The coal gas used for illumina- tion -and for fuel is a mixture of gaseous hydrocarbons of which the chief is H4C.