tinct color, which in many cases at once clearly indicates the individual metal which the analysed compound contains, as is the case, for instance, with cobalt; and (3) whether the bead manifests the same or a different deportment in the outer and in the inner flame. Phenomena of the latter kind arise from the ensuing reduction of higher to lower oxides, or even to the metallic state, and are for some substances particularly characteristic. $ 82. 4. PHOSPHATE OF SODA AND AMMONIA (Microcosmic Salt) Preparation.-Heat to boiling 6 parts of phosphate of soda and 1 part of pure chloride of ammonium with 2 parts of water, and let the solution cool. Free the crystals produced of the double phosphate of soda and ammonia by recrystallization from the chloride of sodium which adheres to them. Dry the purified crystals, and pulverize them for use. Uses. When phosphate of soda and ammonia is subjected to the action of heat, the ammonia escapes with the water of crystallization, and readily fusible metaphosphate of soda is left behind. The action of microcosmic salt is quite analogous to that of biborate of soda. We prefer it, however, in some cases, to borax as a solvent or flux, the beads which it forms with many substances being more beautifully and distinctly colored than those of borax. Platinum wire is also used for a support in the process of fluxing with microcosmic salt; the loop of the wire must be made small and narrow, otherwise the bead will not adhere to it. The operation is conducted as directed in the preceding paragraph. § 83. 5. NITRATE OF PROTOXIDE OF COBALT (Co O, NO,, crystallized + 5 aq.). Preparation. Fuse in a Hessian crucible 3 parts of bisulphate of pota sa and add to the fused mass, in small portions at a time, 1 part of well ted cobalt ore (the purest zaffre you can procure) reduced to fine powder. The mass thickens, and acquires a pasty consistence. Heat now more strongly, until it has become more fluid again, and continue to apply heat until the excess of sulphuric acid is completely expelled, and the mass accordingly no longer emits white fumes. Remove the fused mass now from the crucible with an iron spoon or spatula, let it cool, and reduce it to powder; boil this with water until the undissolved portion presents a soft mass; then filter the rose-red solution, which is free from arsenic and nickel, and mostly also from iron, and remove the copper, &c., from the filtrate by means of hydrosulphuric acid. Filter again, and evaporate the filtrate, with addition of some chlorine water, until it is much concentrated. Mix the concentrated filtrate now with a hot saturated solution of binoxalate of potassa, and let the mixture stand at a gentle heat until the fluid appears colorless. Wash the precipitated oxalate of protoxide of cobalt thoroughly, dry, and heat to redness in a covered platinum or porcelain crucible. This decomposes the oxalate into water and carbonic acid, which escapes, and metallic cobalt, which is left behind. Dissolve a portion of the latter in nitric acid, taking care to avoid a large excess of the solvent; evaporate the solution in the water-bath to dryness, and dissolve 1 part of the residue in 10 parts of water for use. Tests.-Solution of nitrate of protoxide of cobalt must be free from other metals, and especially also from salts of the alkalies; when precipitated with sulphide of ammonium and filtered, the filtrate must, upon evaporation on platinum, leave no fixed residue. Uses.-Protoxide of cobalt forms, upon ignition with certain infusible bodies, peculiarly colored compounds, and may accordingly serve for the detection of these bodies (oxide of zinc, alumina, and magnesia; see Section III.). $84. 6. CHLORIDE OF SILVER (Ag Cl). Preparation. Precipitate solution of nitrate of silver with hydrochloric acid; wash the precipitate, mix it with water to a thick pulp, and keep in a small bottle for use. Uses. Chloride of silver has lately been recommended by Gericke as a means of making the colorations more distinct and lasting which certain bodies, upon exposure to the inner blowpipe flame, impart to the outer flame. I can from my own experience confirm the results arrived at by Gericke. The action of the chloride of silver is owing to the circumstance that this compound loses its chlorine only gradually upon exposure to heat, and gives rise accordingly for a certain time to the formation of metallic chlorides, which it is well known distinct colorations to flame than any other class of salts. Atinum wire would speedily be rendered unfit for use by the reduceder, thin iron wire is employed; every operation requires a new loop. t more SECTION ON THE DEPORTMENT OF BODIES WITH REAGENTS. $ 85. I STATED in my introductory remarks that the operations and experiments of qualitative analysis have for their object the conversion of the unknown constituents of any given compound into forms of which we know the deportment, relations, and properties, and which will accordingly permit us to draw correct inferences regarding the several constituents of which the analysed compound consists. The greater or less value of such analytical experiments, like that of all other inquiries and investigations, depends upon the greater or less degree of certainty with which they lead to definite results, no matter whether of a positive or negative nature. But as a question does not render us any the wiser if we do not know the language in which the answer is returned, so, in like manner, will analytical investigations prove unavailing if we do not understand the mode of expression in which the desired information is conveyed to us; in other words, if we do not know how to interpret the phenomena produced by the action of our reagents upon the substance examined. Before we can therefore proceed to enter upon the practical investiga tions of analytical chemistry, it is indispensable that we should really possess the most perfect knowledge of the deportment, relations, and properties of the new forms into which we intend to convert the substances we wish to analyse. Now, this perfect knowledge consists, in the first place, in a clear conception and comprehension of the conditions necessary for the formation of the new compounds and the manifestation of the various reactions; and, in the second place, in a distinct impression of the color, form, and physical properties which characterize the new compound. This section of the work demands therefore not only the most careful and attentive study, but requires moreover that the student should examine and verify by actual experiment every fact asserted in it. The method usually adopted in elementary works on chemistry is to treat of the various substances and their deportment with reagents individually and separately, and to point out their characteristic reactions. I have, however, in the present work, deemed it more judicious and better adapted to its elementary character, to arrange those substances which are in many respects analogous into groups, and thus, by comparing their analogies with their differences, to place the latter in the clearest possible light. A. DEPORTMENT AND PROPERTIES OF THE METALLIC OXIDES AND OF THEIR RADICALS. $86. Before proceeding to the special study of the several metallic oxides, I give here a general view of the whole of them, classified in groupsshowing which oxides belong to each group. The grounds upon which the classification has been arranged will appear from the special consideration of the several groups. First group Potassa, sodaimonia (lithia). Second group Baryta, strontia, ne, magnesia. Third group Alumina, sesquioxide of chromium (glucina, thorina, noria, yttria, terbia, erbia, zirconia-earths; oxides of cerium, lanthanium, didymium ; oxide of titanium and titanic acid; tantalic acid, niobic acid). Fourth group Oxides of zinc, manganese, nickel, cobalt, iron (uranium). Fifth group Oxides of silver, mercury, lead, bismuth, copper, cadmium (palladium, rhodium, osmium, ruthenium). Sixth group. Oxides and acids of antimony, tin, arsenic, gold, platinum (iridium, molybdenum, tellurium, tungsten, vanadium). Of these metallic oxides only those printed in italics are found extensively and in large quantities in that portion of the earth's crust which is accessible to our investigations; these, therefore, are most important to chemistry, arts and manufactures, agriculture, pharmacy, &c. &c. ; and these therefore we shall dwell upon at greater length. The more important among the remainder are more briefly considered in supplementary paragraphs; and the less important ones are altogether omitted. The deportment of the metals I have given' only in the case of those that are more frequently met with in analytical operations in the metallic state. § 87. FIRST GROUP. POTASSA, SODA, AMMONIA. Properties of the group.-The alkalies are readily soluble in water, as well in the pure or caustic state as in the form of sulphides, carbonates, and phosphates. Accordingly they do not precipitate one another in the pure state, nor as carbonates or phosphates, nor are they precipitated by hydrosulphuric acid under any condition whatever. The solutions of the pure alkalies, as well as of their sulphides and carbonates, restore the blue color of reddened litmus-paper, and impart an intensely brown tint to turmeric paper. Special Reactions. a. POTASSA (K 0). 1. Potassa and its hydrate and salts are not volatile at a faint redheat. Potassa and its hydrate deliquesce in the air; the oily liquids formed do not solidify by absorption of carbonic acid. 2. Nearly the whole of the salts of potassa are readily soluble in water. They are colorless, if the constituent acid is so. The neutral salts of potassa with strong acids do not alter vegetable colors. Carbonate of potassa crystallizes with difficulty, and deliquesces in the air. Sulphate of potassa is anhydrous, and suffers no alteration in the air. 3. Bichloride of platinum produces in the neutral and acid solutions of the salts of potassa a yellow, crystalline, heavy precipitate of BICHLORIDE OF PLATINUM AND CHLORIDE OF POTASSIUM (potassio-bichloride of platinum) (K Cl, Pt Cl1). In concentrated solutions this precipitate separates immediately upon the addition of the reagent: in dilute solutions it forms only after some time, often after a considerable time. Very dilute solutions are not precipitated by the reagent. The precipitate consists of octahedrons discernible under the microscope. Alkaline solutions must be acidified with hydrochloric acid before the bichloride of platinum is added. The precipitate is difficultly soluble in water; the presence of free acids does not greatly increase its solubility; it is insoluble in alcohol. Bichloride of platinum is therefore a particularly delicate test for salts of potassa dissolved in spirit of wine. The best method of applying this reagent is to evaporate the aqueous solution of the potassa salt with bichloride of platinum nearly to dryness on the water-bath, and to pour a little water on the residue, or, better still, some spirit of wine, provided no substances insoluble in that menstruum be present: the potassio-bichloride of platinum is left undissolved. Care must be taken not to confound this double salt with ammonio-bichloride of platinum, which greatly resembles it (see §§ 90, 4). 4. Tartaric acid produces in neutral or alkaline* solutions of salts of potassa―a white, quickly subsiding, granular crystalline precipitate of * In the case of alkaline solutions, the reagent must be added until the fluid shows a strongly acid reaction. 4 BITARTRATE OF POTASSA (K O, HO, C, H, O). In concentrated solutions this precipitate separates immediately; in dilute solutions often only after the lapse of some time. Vigorous shaking or stirring of the fluid promotes its formation considerably. Very dilute solutions are not precipitated by this reagent. Free alkalies and free mineral acids dissolve the precipitate; it is difficultly soluble in cold, but pretty readily soluble in hot water. In the case of acid solutions, the free acid must, if practicable, first be expelled by evaporation and ignition, or the solution must be neutralized with soda or carbonate of soda, before we can proceed to test for potassa with tartaric acid. 5. If a salt of potassa, more particularly chloride of potassium, is held on a platinum wire in the apex of the inner blowpipe flame, the outer flame acquires a VIOLET color. The tint which phosphate and borate of potassa impart to the outer blowpipe flame is scarcely perceptible. Presence of a salt, of soda completely obscures the reaction. Decrepitating salts are pulverized and made to adhere to the wire with water. Addition of chloride of silver promotes the reaction in the case of nitrate, carbonate, &c., of potassa (§ 84). 6. If a salt of potassa (more particularly chloride of potassium) is heated with a small quantity of water, alcohol (burning with colorless flame) added, heated, and then kindled, the flame appears VIOLET. presence of soda obscures this reaction, $ 89. b. SODA (Na O). The 1. Soda and its hydrate and salts present in general the same deportment and properties as potassa and its corresponding compounds. The oily fluid which soda forms by deliquescing in the air, resolidifies speedily by absorption of carbonic acid. Carbonate of soda crystallizes readily; the tabular crystals (Na O, CO, +10 aq.) effloresce rapidly when exposed to the air. The same applies to the prismatic crystals of sulphate of soda (Na O, SO, + 10 aq.). 3 5 2. Antimonate of potassa produces in neutral or feebly alkaline solutions of salts of soda a white, crystalline precipitate of METANTIMONATE OF SODA (Na O, Sb 0, +7 aq.). Vigorous shaking of the mixture promotes its formation. If the fluid, after the addition of the reagent, be stirred with a glass rod, moving the latter along the sides of the vessel, the lines described will, even in very dilute solutions, speedily become visible, since the precipitate forms first on the parts rubbed by the rod. If the precipitate separates slowly, it consists of wellformed microscopic quadrilateral octahedrons. The presence of neutral salts of potassa interferes only slightly with the formation of the precipitate; but carbonate of potassa, when present in larger proportion, wholly prevents its separation from more dilute solutions. In cases, therefore, where the solution under examination contains this salt, it is necessary to precede the application of the antimonate of potassa by addition of hydrochloric or acetic acid until the reaction of the solution remains only feebly alkaline. Acid solutions must first be neutralized with potassa, since otherwise the reagent would suffer decomposition, and hydrated antimonic acid or acid antimonate of potassa be precipitated from it. 3. Salts of soda (more particularly chloride of sodium), when exposed |