William Dittmar

“ Tartrates.—The acid potash salt, , "cream of tartar," is prepared from crude tartar (argol) by dissolving it in hot water, filtering off what remains of tartrate of lime and other impurities, and allowing the filtrate to crystallize. The crystals are generally contaminated with a little of the lime-salt, for the removal of which the best method is to treat the powdered crystals with cold dilute hydrochloric acid and then wash them with cold water by displacement. The lime passes into the filtrate. ”

“ The tinning of a copper basin is an easy operation. The basin, made scrupulously clean, is heated over a charcoal fire to beyond the fusing point of tin. Molten tin is then poured in, a little powdered sal-ammoniac added, and the tin spread over the inside with a bunch of tow. The sal- ammoniac removes the last unavoidable film of oxide, leaving a purely metallic surface, to which the tin adheres firmly. ”

“ TARTARIC ACID, in its ordinary acceptation, refers to one acid, (C4H4O6) H2, which occurs in most acid fruit juices, in association generally with malic or citric, or both. Grape-juice owes its sourness almost entirely to acid tartrate of potash. While the juice ferments into wine, the greater part of the acid tartrate separates out, along with tartrate of lime, colouring matter, and other impurities, as a hard crust adhering to the sides of the cask. Such impure acid tartrate of potash is known commercially as "argol." ”

“ To produce it from a solution of a neutral tartrate, add acetic acid and acetate of potash, and stir vigorously; the salt gradually separates out as a crystalline precipitate. Neutral tartrate solutions, with chloride of calcium, give a precipitate of tartrate of lime, which is at first amorphous, and in this condition dissolves pretty readily in excess of reagent or tartrate, but in general re-separates in the crystalline form (the undissolved tartrate likewise becomes crystalline) on standing. ”

“ The soda tungstate, 5Na2O.12WO3 + xH2O, known as para-tungstate of soda, is made industrially by fusing wolframite with carbonate of soda and lixiviating the fuse with water. The insoluble oxides of iron and manganese are filtered off; the filtrate, while still hot, is nearly neutralized with hydrochloric acid and allowed to crystallize. It forms large crystals containing twenty-one, twenty-five, or twenty-eight times H2O according to the temperature at which they are formed. ”

“ As an elementary substance, it is very similar in its mechanical and physical properties to lead; like lead it forms an almost insoluble chloride and an insoluble iodide. But the hydroxide of thallium, in most of its properties, comes very close to those of the alkali metals; it is strongly basilous, forms an insoluble chloroplatinate, and an alum strikingly similar to the corresponding potassium compounds. Yet, unlike potassium or lead, it forms a feebly basic sesquioxide similar to manganic oxide, Mn2O3.
Traces of thallium exist in many kinds of pyrites, as used for vitriol-making. ”

“ This behaviour of the metal may probably be explained by assuming that in any tin crystal the coefficient of thermic ex pansion has one value in the direction of the principal axis and another in that of either of the subsidiary axes. From to 100 the two coefficients are practically identical ; below -14 and from somewhere above 100 C. upwards they assume different values ; and, as the several crystals are oriented in a lawless fashion, this must tend to disintegrate the mass. Tin fuses at 232 7 (Persoz) ; at a red heat it begins to volatilize slowly ”

“ The whole is then left to itself, when crystals of tin gradually separate out on the bottom of the basin.
Properties of Pure Tin.—An ingot of pure tin is pure white (ex cept for a slight tinge of blue) ; it exhibits considerable lustre and is not subject to tarnishing on exposure to normal air. The metal is pretty soft and easily flattened out under the hammer, but almost devoid of tenacity. That it is elastic, within narrow limits, is proved by its clear ring when struck with a hard body under circumstances permitting of free vibration. ”

“ The washed ore is "roasted" to burn away the arsenic and sulphur and to convert the iron, originally present in the heavy and compact form of pyrites or arsenide, into light friable oxide, which is removed by a second washing process. If much oxide of copper is con tained in the product, it is extracted with dilute sulphuric acid, and from the solution is recovered by precipitation with metallic iron (see COPPER, vol. vi. p. 347) . The puri fied ore, known as "black tin," goes to the smelting furnace. ”

“ The mother liquor includes generally more or less of nickel, cobalt, zinc, and other heavy metals, which, as Wöhler showed, can be removed as insoluble sulphides by the addition of sulphide of ammonium; uranium, under the circumstances, is not precipitated by sulphide of ammonium. The filtrate, on being boiled down, yields a second crop of uranate of ammonia. This uranate when ignited in a platinum crucible leaves a green oxide of the composition U3O8, i.e., artificial pitch-blende, which serves as a starting point for the preparation of uranium compounds. ”

“ The salt is used medicinally, and also for removing free acid from excessively sour wine by formation of relatively insoluble bitartrate (Liebig's method) .
Rochelle salt, , is prepared by not quite neutralizing hot solution of carbonate of soda with powdered cream of tartar. The (filtered) hot solution deposits on cooling magnificent crystals, readily soluble in water, though less so than the unmixed potash salt. Rochelle salt is used as a mild purgative. The so-called Seidlitz powders are effervescing powders with a considerable addition of Rochelle salt to the bicarbonate. ”

“ When heated in air it is readily oxidized, with formation of a reddish or violet vapour. When exposed to the air it readily draws a film of oxide; the tarnished metal when plunged into water reassumes its metallic lustre, the oxide film being quickly dissolved. ”

“ The metal is prepared from the pure oxide WO3 by reduction with hydrogen in a platinum tube at a high temperature. It forms resplendent tin-white or grey plates, or a dull black powder similar to hydrogen-reduced iron. ”

“ This native oxide of tin, SnO.,, forms very hard quadratic crystals of specific gravity 6 8. The pure mineral is colourless, and it is very scarce; most specimens are brown owing to the presence of ferric or manganic oxide. The faces of the crystals exhibit diamond lustre. There is also another native form, known as " wood tin," occurring in roundish masses with a fibrous radiating fracture. The ore is found in veins or layers within the older crystalline rocks and slates. ”

“ Tin compounds when heated on charcoal with car bonate of soda in the reducing blowpipe flame yield metal and a scanty ring of white SnO^ The reduction, however, succeeds better with cyanide of potassium as a flux. Stannous salt solutions yield a brown precipitate of SnS with sulphuretted hydrogen, which is insoluble in cold dilute acids and in real sulphide of ammonium, (NH 4 ) 2 S; but the yellow, or the colourless reagent on addition of sulphur, dissolves the precipitate as SnS 2 salt. The solution on acidification yields a yellow precipitate of this sulphide. ”

“ A similar oxide is produced by burning tin in air at high temperatures or exposing any of the hydrates to a strong red heat. Such tin-ash, as it is called, is used for the polishing of optical glasses. (3) Meta-stannic acid (H 2 OSnO 2, generally written Hi Sn 5 15, to account for the complicated composition of metastan nates, e.g., the soda salt H 8 Na.,Sn 5 pj 5 ) is the white hydrate produced from the metal by means of nitric acid. It is insoluble in water and in nitric acid and apparently so in hydrochloric acid ”

“ A solution of the pure salt yields fine prisms of the composition Na-jSiiOj + lOHgO, which effloresce in the air. The salt is much used as a mordant in dyeing and calico-printing. Alkaline and other stannates when treated with aqueous hydrofluoric acid are converted into fluo-stannates (e.g., K2SnO 3 into K 2 SnF 6 ) , which are closely analogous to, and isomorphous with, fluo-silicates. ”

“ Hence he concluded that the uranium salt is Ur2O3.3SO3, where Ur2O3, according to his analysis, represents 864 parts of yellow oxide, if Fe2O3 = 160 or O = 16. Like Fe2O3, the yellow oxide lost 48 parts of oxygen per Ur2O3 = 864 parts as water, while Ur2 = 816 parts of metal remained. [1] These results were universally adopted until Péligot in 1840 discovered that Berzelius's (and Klaproth's) metal contains oxygen, and that his (Ur2) O3 really is (U6O6) .O3 = 3U2O3, where U = 120 is one atomic weight of real uranium. ”

“ During the roasting process the ore must be constantly agitated to prevent caking, and to bring the arseniferous, &c., parts to the surface. To save manual labour, Oxland and Hocking have constructed a mechanical roaster. ”

“ The chloride readily com bines with water into an easily soluble crystallizable hydrate ("tin crystals ") . This is made without difficulty by dissolving tin in strong hydrochloric acid and allowing it to crystallize. For its industrial preparation Nollner passes sufficiently hydrated hydrohydrochloric acid gas over granulated tin contained in stoneware bottles and evaporates the concentrated solution produced in tin basins over granulated tin. The basin itself is not attacked. The crystals contain one H 2 according to Berzelius, while Marignac finds two ”

“ Uranic Compounds.— By keeping the nitrate UO2 (NO3) 2 at a temperature of 250° for a sufficient time the oxide UO3 is obtained as a chamois-yellow solid, insoluble in water, but soluble in acids, with the formation of uranyl salts, UO2.Cl2, &c. ”

“ Its crystalline struc ture must account for the striking fact that the ingot, when exposed for a sufficient time to very low temperatures (to -39 C. for 14 hours) , becomes so brittle that it falls into powder under a pestle or hammer ; it indeed sometimes crumbles into powder spontaneously. At ordinaiy temperatures tin proves fairly ductile under the hammer, and its ductility seems to increase as the temperature rises up to about 100 C. At some temperature near its fusing point it be comes brittle (vide supra) , and still more brittle from - 14 C. downwards. ”