Podophyllin is a resinous powder obtained by precipitating an alcoholic tincture of the rhizome by means of water acidulated with hydrochloric acid.
Except such as are of coral formation, the Antilles are hilly, not to say mountainous, their summits rising in places to an elevation of 8000 ft., and nearly all, prior to their occupation by Europeans, were covered with luxuriant forest, which, assisting in the collection and condensation of the clouds brought by the trade winds, ensured its own vitality by precipitating frequent and long-continued rains; upon the fertile soil.
Freeing from the other substances in the solution, can be accomplished in the precipitating vessel.
Napoleon had from the first been aware of the secret alliance between Prussia and Russia, sworn by their respective sovereigns over the grave of Frederick the Great, and this knowledge had been his principal reason for precipitating hostilities with the former.
The putrefaction of the latter sets free sulphuretted hydrogen, which then acts on the iron compounds, precipitating ferrous sulphide.
Lead fluoride, PbF2, is a white powder obtained by precipitating a lead salt with a soluble fluoride; it is sparingly soluble in water but readily dissolves in hydrochloric and nitric acids.
The normal ortho-phosphate, Pb3(P04)2, is a white precipitate obtained by adding sodium phosphate to lead acetate; the acid phosphate, PbHPO 4, is produced by precipitating a boiling solution of lead nitrate with phosphoric acid; the pyrophosphate and meta-phosphate are similar white precipitates.
Lead chromate, PbCrO 4, is prepared industrially as a yellow pigment, chrome yellow, by precipitating sugar of lead solution with potassium bichromate.
Uranous hydrate is obtained as reddish-brown flakes by precipitating a uranous solution with alkali.
Various hydrates have been described, but they cannot be formed by precipitating a uranyl salt with an alkali, this reagent giving rise to salts termed uranates.
It may be separated by shaking out with dilute sulphuric acid, and then precipitating the sulphuric acid solution with potassium bichromate, the resulting acridine bichromate being decomposed by ammonia.
Zinc carbonate, ZnCO 3, occurs in nature as the mineral calamine (q.v.), but has never been prepared artificially, basic carbonates, ZnCO 3 .xZn(OH) 2, where x is variable, being obtained by precipitating a solution of the sulphate or chloride with sodium carbonate.
Zinc may be quantitatively estimated by precipitating as basic carbonate, which is dried and ignited to zinc oxide.
This salt is prepared by precipitating a solution of gold in aqua regia by ammonia, and then introducing the well-washed precipitate into a boiling solution of potassium cyanide.
The acid, auricyanic acid, 2HAu (CN) 4.3H20, is obtained by treating the silver salt (obtained by precipitating the potassium salt with silver nitrate) with hydrochloric acid; it forms tabular crystals, readily soluble in water, alcohol and ether.
Forming the soluble gold chloride and then precipitating the metal; 4.
Dissolving the gold in potassium cyanide solution, and then precipitating the metal; 5.
After settling the solution is run into the precipitating tanks.
The liquors are run off from the vats to the electrolysing baths or precipitating tanks, and the leached ores are removed by means of doors in the sides of the vats into wagons.
According to Christy, the precipitation with zinc follows equations for 2 according as potassium cyanide is present or not: (1) 4 KAu(CN)2+4Zn+2H20=2Zn(CN)2+ K 2 Zn(CN) 4 +Zn(OK) 2 +4H+4Au; (2) 2KAu (CN) 2 +3Zn+4KCN+2H 2 0 = 2K 2 Zn(CN) 4 +Zn(OK) 2 +4H+2Au; one part of zinc precipitating 3.1 parts of gold in the first case, and 2.06 in the second.
The precipitating boxes, generally made of wood but sometimes of steel, and set on an incline, are divided by partitions into alternately wide and narrow compartments, so that the liquor travels upwards in its passage through the wide divisions and downwards through the narrow divisions.
The slime is cleaned out fortnightly or monthly, the zinc turnings being cleaned by rubbing and the supernatant liquor allowed to settle in the precipitating boxes or in separate vessels.
Or Gutzkow's method of precipitating the metal with ferrous sulphate may be employed.
Hampe prepared chemically pure bismuth by fusing the metal with sodium carbonate and sulphur, dissolving the bismuth sulphide so formed in nitric acid, precipitating the bismuth as the basic nitrate, redissolving this salt in nitric acid, and then precipitating with ammonia.
Calcium fluoride, CaF2, constitutes the mineral fluor-spar, and is prepared artificially as an insoluble white powder by precipitating a solution of calcium chloride with a soluble fluoride.
Ammonium chlorate, NH 4 C10 3, is obtained by neutralizing chloric acid with either ammonia or ammonium carbonate, or by precipitating barium, strontium or calcium chlorates with ammonium carbonate.
Ammonium nitrite, NH 4 NO 2, is formed by oxidizing ammonia with ozone or hydrogen peroxide; by precipitating barium or lead nitrites with ammonium sulphate, or silver nitrite with ammonium chloride.
When dissolved in water it yields some NaOH and H202; on crystallizing a cold 'solution Na202.8H20 separates as large tabular hexagonal crystals, which on drying over sulphuric acid give Na 2 0 2.2H 2 0; the former is also obtained by precipitating a mixture of caustic soda and hydrogen peroxide solutions with alcohol.
The acid sulphite, NaHSO 3, obtained by saturating a cold solution of the carbonate with sulphur dioxide and precipitating by alcohol, is employed for sterilizing beer casks.
He accepted the chairmanship of the Royal Commission on Ritualistic Practices in the Church, and he did valuable work as 'an arbitrator; and though when the fiscal controversy arose he became a member of the Free-food League, his parliamentary loyalty to Mr Balfour did much to prevent the Unionist free-traders from precipitating a rupture.
They may be extracted by exhausting the plant-tissues with a dilute acid, and precipitating the bases with potash, soda, lime or magnesia.
Chromous oxide, CrO, is unknown in the free state, but in the hydrated condition as Cr04H 2 0 or Cr(OH) 2 it may be prepared by precipitating chromous chloride by a solution of potassium hydroxide in air-free water.
Chromic sulphate, Cr2(S04)3, is prepared by mixing the hydroxide with concentrated sulphuric acid and allowing the mixture to stand, a green solution is first formed which gradually changes to blue, and deposits violet-blue crystals, which are purified by dissolving in water and then precipitating with alcohol.
Magnesium hydroxide Mg(OH) 2, occurs native as the minerals brucite and nemalite, and is prepared by precipitating solutions of magnesium salts by means of caustic soda or potash.
It is not possible to prepare the normal carbonate by precipitating magnesium salts with sodium carbonate.
Aluminium phosphates may be prepared by precipitating a soluble aluminium salt with sodium phosphate.
The free pararosaniline, C19H19N30, and rosaniline, C20H21N30, may be obtained by precipitating solutions of their salts with a caustic alkali, colourless precipitates being obtained, which crystallize from hot water in the form of needles or plates.
Lanthanum hydroxide, La(OH) 3, is a white amorphous powder formed by precipitating lanthanum salts by potassium hydroxide.
Sodium Permanganate, NaMn0 4.3H 2 O (?), may be prepared in a similar manner, or by precipitating the silver salt with sodium chloride.
The sulphides can be removed by " oxidizing " them into thiosulphates by means of atmospheric air, with or without the assistance of other agents, such as manganese peroxide; or by " carbonating " them with lime-kiln or other gases containing carbon dioxide; or by precipitating them with lead or zinc oxide.
The metal is obtained from zinc blende (which only contains it in very small quantity) by dissolving the mineral in an acid, and precipitating the gallium by metallic zinc. The precipitate is dissolved in hydrochloric acid and foreign metals are removed by sulphuretted hydrogen; the residual liquid being then fractionally precipitated by sodium carbonate, which throws out the gallium before the zinc. This precipitate is converted into gallium sulphate and finally into a pure specimen of the oxide, from which the metal is obtained by the electrolysis of an alkaline solution.
By precipitating a thorium salt with a fluoride, a gelatinous hydrate, ThF 4.4H 2 O, is obtained.
Tungstic acid, H 2 W0 4, is obtained as H 2 W0 4 H 2 0 by precipitating a tungstate with cold acid; this substance has a bitter taste and its aqueous solution reddens litmus.
The trisulphide, WS3, is obtained by dissolving the trioxide in ammonium sulphide or by passing sulphuretted hydrogen into a solution of a tungstate and precipitating by an acid in both cases.
The heaps are moistened with ferric chloride solution, and the reaction is maintained by the liquid percolating through the heap. The liquid is run off at the base of the heaps into the precipitating tanks, where the copper is thrown down by means of metallic iron.
Soc., 1906, 3, p. 39.) Cupric phosphate, Cu 3 (PO 4) 2, may be obtained by precipitating a copper solution with sodium phosphate.
The corresponding hydroxide, orthoantimonious acid, Sb(OH) 31 can be obtained in a somewhat impure form by precipitating tartar emetic with dilute sulphuric acid; or bet::er by decomposing antimonyl tartaric acid with sulphuric acid and drying the precipitated white powder at too° C. Antimony tetroxide is formed by strongly heating either the trioxide or pentoxide.
The amorphous variety may be obtained from the crystalline form by dissolving it in caustic potash or soda or in solutions of alkaline sulphides, and precipitating the hot solution by dilute sulphuric acid.
On precipitating antimony trichloride or tartar emetic in acid solution with sulphuretted hydrogen, an orange-red precipitate of the hydrated sulphide is obtained, which turns black on being heated to 200° C The trisulphide heated in a current of hydrogen is reduced to the metallic state; it burns in air forming the tetroxide, and is soluble in concentrated hydrochloric acid, in solutions of the caustic alkalis, and in alkaline sulphides.
Antimony nentasulphide, Sb2S5, is prepared by precipitating a solution of the pentachloride with sulphuretted hydrogen, by decomposing "Schlippe's salt" with an acid, or by passing sulphuretted hydrogen into water containing antimonic acid.
It is obtained as a light yellow powder by dissolving the metal in hydriodic acid, or by precipitating a silver salt with a soluble iodide.
Silver sulphide, Ag 2 S, constitutes the mineral argentite or silver glance, and may be obtained by heating silver with sulphur, or by precipitating a silver salt with sulphuretted hydrogen.
Carum copticum, from which it may be extracted by shaking with potassium hydroxide, filtering and precipitating the phenol with hydrochloric acid.
Phosphorous acid, P(OH) 3, discovered by Davy in 1812, may be ' obtained by dissolving its anhydride, P 4 0 61 in cold water; by immersing sticks of phosphorus in a solution of copper sulphate contained in a well-closed flask, filtering from the copper sulphide and precipitating the sulphuric acid simultaneously formed by baryta water, and concentrating the solution in vacuo; or by passing chlorine into melted phosphorus covered with water, the first formed phosphorus trichloride being decomposed by the water into phosphorous and hydrochloric acids.
Two series of synthetic hydrates were recognized by Muck and Tommasi: the " red " hydrates, obtained by precipitating ferric salts with alkalis, and the " yellow " hydrates, obtained by oxidizing moist ferrous hydroxide or carbonates.
It is also prepared by precipitating a ferric salt with ammonium sulphide; unless the alkali be in excess a mixture of ferrous sulphide and sulphur is obtained.
Ferri hydroxidum (U.S.P.), the hydrated oxide of iron, made by precipitating ferric sulphate with ammonia, is used solely as an antidote in arsenical poisoning.
It is a strong reducing agent, giving a precipitate of cuprous oxide from alkaline copper solutions at ordinary temperature, converting mercuric chloride to mercurous chloride, and precipitating metallic silver from solutions of silver salts.
Lead chromate, PbCrO 4, occurs native as the mineral crocoisite, and may be obtained as an amorphous pale yellow solid by precipitating a soluble lead salt by an alkaline chromate.
Another process consists in adding water to the solution and so precipitating the bismuth as oxychloride, which is then converted into the metal.
The silver solution, collected in a circular precipitating vat (10 ft.