9. The Characteristics of Thallium'-Derived from statements of Crookes, Lamy and Böttger, and from original observations.-Thallium occurs in minute quantities in many native metallic sulphids, especially in iron and copper pyrites. Hence it is often found in commercial sulphur, in oil-of-vitriol and in the sediment of the sulphuric acid chambers in metallic copper, bismuth and cadmium, and in preparations derived from these substances. It likewise occurs in the flue-dust of furnaces and in certain mineral springs. Thallium is a bluish-white, very soft and malleable, though not tenacious, metal. Its sp. gr.11.8. It is brilliant on a fresh-cut surface, but shortly tarnishes. It is easily fusible and volatilizes at a red heat. Before the blowpipe it emits copious fumes of oxyd which have a peculiar odor and exhibit a play of white, reddish and violet colors. In its chemical relations, thallium, in some respects, most resembles lead and silver; in others it is allied to the alkali-metals. It slowly dissolves in distilled water (far less readily in water containing earthy salts), especially when in a state of fine division. It dissolves readily in sulphuric and nitric acids and aqua-regia, slowly in chlorhydric and very slowly in acetic acid. Boiled with aqua-regia, terchlorid of thallium escapes in the vapors. Of the compounds of thallium with oxygen, there are known the protoxyd (TO) and the teroxyd (TIO3). The latter is violet-black or brown, insoluble in water, soluble in hot strong sulphuric acid. Its hydrate (TIO, HO) is brown and dissolves in chlorhydric, nitric and sulphuric acids. At high temperatures it loses its water but retains its brown color. On strong ignition the teroxyd loses oxygen and is converted into protoxyd. Protoxyd of thallium as hydrate is largely soluble in water and alcohol. Its solution reddens litmus, is caustic and alkaline; by evaporation in vacuo it is obtained crystallized in the form of yellow needles. It absorbs carbonic acid with avidity, unites with acids yielding crystallizable mostly soluble salts. Sulphydric acid does not affect acid solutions of thallium, but throws down from alkaline, as sulphid of ammonium does from neutral solutions, all the thallium they contain, as black sulphid of thallium. In very dilute solutions, a yellow, brownishyellow or red-brown coloration is at first produced. On heating, the liquid may become purplish or blue by transmitted and yellow or brownish-red by reflected light from the suspended particles of sulphid, while the latter, when deposited, has a brownish tinge. Sulphid of thallium is characterized by its flocculent form and bulkiness: its separation is promoted by heating or agitation, and at the same time it becomes less voluminous. Sulphid of thallium is insoluble in sulphid of ammonium, in alkalies, alkaline carbonates and cyanids. It oxydizes to soluble sulphate on exposure in the moist state to the air, and must hence be washed with dilute sulphid of ammonium. It is slowly but perceptibly soluble in cold dilute acetic, chlorhydric and sulphuric acids, especially when exposed to the air, as happens when it is treated on a filter with these acids. It is readily soluble in nitric acid.—Alkalies and alkaline carbonates produce no precipitates in solutions of thallium.-Chlorhydric acid throws down from solutions that are not too dilute, protochlorid of thal1 From the Editor's notes to a new edition of Fresenius' Qualitative Analysis in preparation, to be published by John Wiley, New York. AM. JOUR. SCI.-SECOND SERIES, VOL. XXXVII, No. 109.—JAN., 1864. Bouis on the Capryl series and the observations made by that chemist on the action of sodium upon the chlorid of Capryl.-W. G.] 8. On compounds of silicium with oxygen and hydrogen.-WÖHLER has obtained combinations of silicium with hydrogen and oxygen by the action of fuming chlorhydric acid upon an alloy of silicium and calcium, consisting essentially of CaSi. The siliciuret of calcium is gradually converted with evolution of hydrogen into a new substance which the author calls Silicon, not observing apparently that this name had already been frequently applied to silicium to indicate its analogy with carbon. The silicone as we will write it to prevent confusion-is to be filtered off, thoroughly washed, pressed between folds of porous paper and dried over sulphuric acid, every precaution being taken to exclude light as much as possible. Silicone has a bright orange, yellow color; it is insoluble in water and alcohol and by heating becomes transiently of a deep orange yellow. More strongly heated it takes fire and burns, leaving silicic acid colored brown by amorphous silicium. Heated out of contact with the air it gives off hydrogen and leaves a mixture of silicic acid and silicium in brilliant blackish-brown leaves. When heated in a closed tube with water to a temperature of 190° C., silicone is rapidly and completely converted into white leaves of pure silicic acid while the tube contains compressed hydrogen. Light decomposes silicone with evolution of hydrogen gas, even beneath the surface of water, yielding a white substance which Wöhler terms leucon and which we will write leucone. Neither chlorine nor fuming nitric or concentrated sulphuric acid attack silicone. Fluohydric acid renders it at first white and then dissolves it. Alkaline solutions instantly convert silicone into silicic acid with strong evolution of hydrogen. In the presence of an alkali silicone reduces many metallic solutions, the evolved hydrogen being probably the reducing agent. The analyses of silicone lead to the formula Si, H.O as most probable, though the formulas Sig H2O, or Si, 2H,O, express the results of two of the analyses better. Wöhler points out the analogy of these formulas to those of organic substances and suggests that there may hereafter be a special chemistry of the compounds of silicium as those of carbon. Leucone is a colorless body which appears to remain unchanged in the air. On heating in the air it behaves like silicone, which it also resembles in its behavior toward alkalies. Its formula appears to be Si,H,O or possibly SiH6010. Wöhler now considers it probable that the hydrated oxyd of silicium formerly described by Buff and himself, is really leucon and that the corresponding chlorid, bromid and iodid, have respectively the formulas Si,H.Cl,o, Si,H,Br,o, and Si,H,L10 while if the former analyses were correct the formula of leucon would be SiH4010. By the action of dilute chlorhydric acid upon CaSi2 Wöhler obtained another compound of silicon, hydrogen and oxygen as a colorless body which ignited spontaneously in the air. Its formula is possibly Si,H,O10. Compounds containing sulphur, selenium and tellurium were also obtained, but only imperfectly examined. The sulphur compound explodes violently when heated in a tube.-Ann. der Chemie und Pharm., cxxvii, 257. 8 5 10 10° 8 8 8 3 4 6 4 101 4 6 8 4 6 W. G. 9. The Characteristics of Thallium'-Derived from statements of Crookes, Lamy and Böttger, and from original observations.-Thallium occurs in minute quantities in many native metallic sulphids, especially in iron and copper pyrites. Hence it is often found in commercial sulphur, in oil-of-vitriol and in the sediment of the sulphuric acid chambers in metallic copper, bismuth and cadmium, and in preparations derived from these substances. It likewise occurs in the flue-dust of furnaces and in certain mineral springs. Thallium is a bluish-white, very soft and malleable, though not tenacious, metal. Its sp. gr. 118. It is brilliant on a fresh-cut surface, but shortly tarnishes. It is easily fusible and volatilizes at a red heat. Before the blowpipe it emits copious fumes of oxyd which have a peculiar odor and exhibit a play of white, reddish and violet colors. In its chemical relations, thallium, in some respects, most resembles lead and silver; in others it is allied to the alkali-metals. It slowly dissolves in distilled water (far less readily in water containing earthy salts), especially when in a state of fine division. It dissolves readily in sulphuric and nitric acids and aqua-regia, slowly in chlorhydric and very slowly in acetic acid. Boiled with aqua-regia, terchlorid of thallium escapes in the vapors. Of the compounds of thallium with oxygen, there are known the protoxyd (TO) and the teroxyd (TIO3). The latter is violet-black or brown, insoluble in water, soluble in hot strong sulphuric acid. Its hydrate (TIO, HO) is brown and dissolves in chlorhydric, nitric and sulphuric acids. At high temperatures it loses its water but retains its brown color. On strong ignition the teroxyd loses oxygen and is converted into protoxyd. Protoxyd of thallium as hydrate is largely soluble in water and alcohol. Its solution reddens litmus, is caustic and alkaline; by evaporation in vacuo it is obtained crystallized in the form of yellow needles. It absorbs carbonic acid with avidity, unites with acids yielding crystallizable mostly soluble salts. Sulphydric acid does not affect acid solutions of thallium, but throws down from alkaline, as sulphid of ammonium does from neutral solutions, all the thallium they contain, as black sulphid of thallium. In very dilute solutions, a yellow, brownishyellow or red-brown coloration is at first produced. On heating, the liquid may become purplish or blue by transmitted and yellow or brownish-red by reflected light from the suspended particles of sulphid, while the latter, when deposited, has a brownish tinge. Sulphid of thallium is characterized by its flocculent form and bulkiness: its separation is promoted by heating or agitation, and at the same time it becomes less voluminous. Sulphid of thallium is insoluble in sulphid of ammonium, in alkalies, alkaline carbonates and cyanids. It oxydizes to soluble sulphate on exposure in the moist state to the air, and must hence be washed with dilute sulphid of ammonium. It is slowly but perceptibly soluble in cold dilute acetic, chlorhydric and sulphuric acids, especially when exposed to the air, as happens when it is treated on a filter with these acids. It is readily soluble in nitric acid.—Alkalies and alkaline carbonates produce no precipitates in solutions of thallium.-Chlorhydric acid throws down from solutions that are not too dilute, protochlorid of thal1 From the Editor's notes to a new edition of Fresenius' Qualitative Analysis in preparation, to be published by John Wiley, New York. AM. JOUR. SCI.-SECOND SERIES, VOL. XXXVII, No. 109.—JAN., 1864. lium as a white curdy quickly-subsiding precipitate, which requires 50 parts of boiling water and 200 parts of cold water for its solution, and is less soluble in water containing chlorhydric acid.-Iodid of potassium (next to sulphid of ammonium the most sensitive reagent) gives a pale yellow precipitate of iodid of thallium, which appears to be slightly soluble either in water or excess of the reagent.-Bichlorid of platinum throws down a pale orange precipitate of platinchlorid of thallium which is slightly soluble in water and is decomposed on ignition, evolving chlorine with loss of thallium and leaves a crystalline alloy of platinum and thallium.-Metallic zinc separates all the thallium in the metallic state, from neutral solutions often in the form of brilliant radiated needle-shaped crystals, from acid solutions as a heavy black powder. Thallium is in many cases most easily and certainly detected by spectral analysis. The spectrum is characterized by a single bright green line coincident with Bad. This line is however usually perceptible for but a moment, owing to the volatility of the thallium compound, and hence its intensity and duration do not safely indicate the richness in thallium of pyrites, flue-dust, &c. Of crude sulphur a piece as large as a pea is nearly burned away on a platinum loop and the residue is examined in the spectroscope; or better, the sulphur is mostly dissolved by means of sulphid of carbon, and what remains is tested spectrally. In pyrites, flue-dust, and lead-chamber sediment, it may be usually detected at once by the spectroscope. The sublimate procured by strongly heating finely pulverized native sulphids in a closed tube, often gives the reaction when none can be obtained directly from the sulphids themselves. ANALYTICAL CHEMISTRY. S. W. J. 10. Estimation of Sulphuric Acid in salts of the alkalies.—It is well known that precipitated sulphate of baryta may retain alkaline salts in quantities of 15 to 2 per cent, which cannot be removed by the most careful washing. STOLBA (Dingler's Polyt. Jour., April, 1863) obtains the sulphate of baryta pure by digesting it (after washing until the washwaters no longer react of baryta) with 40-50 c. c. of a cold saturated solution of neutral acetate of copper and some acetic acid, at nearly a boiling heat, for 10-15 minutes. (The commercial crystallized acetate of copper is purified from sulphuric acid and at the same time saturated with sulphate of baryta, by adding to its boiling solution a slight excess of chlorid of barium and acetic acid and filtering from the precipitate.) During the digestion, enough acetic acid must be present to prevent the formation of basic salt on boiling. Should basic salt form, which may be readily perceived at the bottom of the vessel, more acetic acid must be added, and the digestion must be renewed for 10-15 minutes. During the process, the vessel containing the precipitate should be constantly agitated. The alkaline salts retained by the sulphate of baryta undergo double decomposition with acetate of copper, and the resulting products all admit of entire separation from the precipitate by means of hot water. The precipitate is washed until no reaction for copper is manifest on mixing the washings with ferrocyanid of potassium. This method the author also found satisfactory for the estimation of sulphuric acid in presence of a large excess of nitrate of baryta and chlorid of barium. S. W. J. PHOTOGRAPHY.— 11. Dry Process; by MM. TEISSERE et JACQUEMET, of Marseilles.Any collodion which gives good results by the wet process may be used in this, provided that it contains at least one per cent of iodids and per cent of bromids. The following formula is recommended : The plate is covered as usual, and sensitized in a bath containing Distilled water, Nitrate of silver, Glacial acetic acid, 100 cub. c. m. 2 cub. c. m. The plate is then transferred to a bath of distilled and filtered water, where it should remain until the plate ceases to appear oily. It is then passed successively through three other baths of filtered water. In the first two, filtered spring water may be used, but the last should be filled with distilled water. The plate is next washed in a solution of tannin, containing 100 cub. c. m. 3 grams. dissolved in the In preparing this solution the tannin should be first pure water, and filtered before the alcohol is added. Before applying the preservative, two portions of the solution should be measured out and placed in separate glasses. That from the first glass should be poured over the plate several times, until the coating has been thoroughly soaked. The excess is then drained off and the plate washed over with the solution in the second glass, which may be collected and used for the first treatment of a second plate. Lastly, the plate is washed under a tap supplied with pure water to remove the excess of tannin, and air dried. The time of exposure for views is stated as from 1 to 14 minutes with a quarter plate Jamin view-lens of 10 c. m. focus, under best conditions. Before developing, the edges of the plate should be varnished with a fine camel's hair brush. Having soaked the plate for a few minutes in pure water, it is next dipped in the silver bath used for sensitizing and drained. It is then dipped into a shallow flat glass dish containing a sufficient quantity of the following developer: Distilled water, Glacial acetic acid, 200 cub. c. m, By rocking the dish the liquid is kept continually rolling over the surface, and the development is carefully watched by the light transmitted through the glass. If the exposure has been well timed the image will appear slowly, but with all the details sharply defined and the lights wholly unstained. It is then only necessary to add to the developer, a few drops at a time, of a weak solution of nitrate silver until the blacks are sufficiently intense * 28-34 cubic centimeters = 1 liquid ounce. 1 gram 154 grains. |