Sulphuretted hydrogen sulphuric acid

JReaetkn. —1. Becomposed by boiling hydrochloric acid, into antimonious chloride, sulphuretted hydrogen, and sulphur —... 

Selenic Acid.—Selenic Acid, H2Se04, is also a il colourless syrupy liquid it can be produced by direct oxidation of selenium by chlorine water, but on concentra-I tion the resulting hydrochloric acid reduces the selenic acid I to selenious acid, as hydriodic acid reduces sulphuric acid. It is best prepared by addition of copper carbonate to the mixture of selenic and hydrochloric acids obtained in that way selenate and chloride of copper are formed the 1 mixture is evaporated to dryness, and the copper chloride is dissolved out with alcohol, leaving the insoluble selenate 1 behind. The selenate is dissolved in water, and on treatment with sulphuretted hydrogen, copper sulphide is precipitated, and removed by filtration the selenic acid is then concentrated if it contains a trace of water, it is a heavy liquid 5 but if quite anhydrous, it forms a solid, melting at 58°. 

Carmine-red is prepared from the lake obtained by precipitating a cochineal decoction with lead acetate. This lead lake is dissolved in dilute sulphuric acid, freed from lead by sulphuretted hydrogen, and boiled with very dilute sulphuric acid for some hours. Barium carbonate is added till a violet coloration ensues, and then filtered rapidly and precipitated with lead acetate. The lead lake is decomposed and the filtrate evaporated to dryness in vacuo. 

If any zinc is present, boil the acid filtrate from the sulphides, neutralise in the cold with sodium carbonate and sodium acetate, and pass in sulphuretted hydrogen—this causes the precipitation of zinc sulphide. Filter, wash, and redissolve in dilute sulphuric acid. Boil the solution, allow to cool, add ammonia and ammonium oxalate, and electrolyse. 

Pure Sulpl urous Acid. In order to prepare sulphurous acid from sul-phurio acid and charcoal, it is better to employ an acid of. 74 per cent, or 1.825 specific gravity. If we take a stronger acid, a part of it is entirely deoxidized to sulphur, and if weaker acid be employed, sulphuretted hydrogen is evolved. To obtain solutely pure sulphurous acid, it is well to put sulphite of lew and coarse charcoal in tne wash bottle. With these precautions, it is possible to obtain pure sulphurous acid from sulphuric acid and charcoal. 

CThemicallv pure oxalic odd is best prepared by precipitating a solution of binoxaluto of pot h xnth acetate of lead, washing tho precipitate with water, and decomposing it, while still moist, with dilute sulphuric acid or sulphuretted hydrogen. Filter and evaporate gently, so that crystals may form aa it cools. 

Sulphocyanide of Ammonium. Saturate 2 parts of common water of ammonia (specific gravity 0.950) with sulphuretted hydrogen and add 6 ports of the same ammonia. To this mixture add 2 parts of sulphur, and the product of the distillation of 6 parts of pnissiate of potash, 3 of sulphuric acid, and 18 of water. Digest till the sulphur is no longer acted on, and the liquid becomes yellow. Boil tho liquid till it becomes colorless, filter, evaporate, and crystallize. 

Properties of the Vermilion of Antimony.—The vermilion of antimony is in the state of a very fine powder, without taste or smell, and is insoluble in water, alcohol, or essential oils. It is but little acted upon by the weak acids, even when concentrated, or by the powerful inorganic acids which have been diluted with water. It stands the latter acids better than the ordinary sulphide of antimony. Concentrated and hot hydrochloric acid dissolves it, with formation of sulphuretted hydrogen and chloride of antimony. Nitric acid oxidises it, with the production of sulphuric and antimonic acids. The vermilion of antimony is not sensibly acted upon by ammonia or the alkaline carbonates on the other hand, the powerful caustic alkalies, such as potash, soda, baryta, strontia, and lime, decompose it and form combinations which are colourless, or nearly so. The colour is therefore destroyed consequently this pigment should not be mixed with alkaline substances. A high temperature blackens it, and should the heat be such as to melt it, it becomes ordinary svilphide of antimony. 

The solutions required are iodic acid, 50 grms. in 250 c.c. deci-normal sodium thiosulphate 20 per cent, potassium iodide and starch paste. Into the flask of a Fresenius or Mohr s iodometric apparatus, 0-5-0-6 gramme of antimonious oxide is weighed, 20-25 c.c. of iodic acid are added, and 10 c.c. of potassium iodide solution are placed in the condensing apparatus. The contents of the flask are boiled until colourless, and the collected iodine determined with thiosulphate. From antimony compounds the sulphide is precipitated by sulphuretted hydrogen, then dissolved in HCl, and the oxide obtained by the action of sodium carbonate. The halogen acids, sulphurous acid, and sulphuretted hydrogen must be dissolved in... 

Iodic acid is decomposed, iodine being separated by hydrochloric and hydrobromic acids, also by sulphuretted hydrogen and sulphurous acid. It may, therefore, be recognised by using any of these re-agents, followed by starch, to detect the free iodine. 

Sulphur occurs, especially in volcanic districts, in a state of purity, often crystallised. It is also found in combination with o gen, as sulphuric acid, in gypsum, heavy spar, and many other minerals, with hydrogen as sulphuretted hydrogen, or mineral waters, and above all with metals, most abundantly with lead, iron, copper, c. c. Finally, it is an essential ingredient of vegetable and animal fibrine, albumen, and caseine, and as such is indispensable to vegetation and to animal life. Some essential oils, such as those of mustard, of horse-radish, of assafcetida, c., contain a large proportion of sulphur. 

Sys. Hydrosulphuric Acid.—This compound is formed when hydrogen and sulphur come in contact in the nascent state. It is best prepared by causing diluted hydrochloric or sulphuric acid to act on sulphuret of iron in the apparatus, p. 46, when sulphuretted hydrogen is disengaged as a gas, which may be collected over warm water, or solution of sSt. The action is as follows Fe S -f H Cl = Fe Cl -b HS. 

This gas is combustible, burning with a bluish flame, and producing sulphurous acid gas and water. Its Sp. G. is 1 177. Water absorbs 2 or 3 times its volume of the gas, and acquires its smell and a nauseous sweetish taste. By contact with the air, the solution is gradually decomposed water is formed and sulphur deposited. Sulphuretted hydrogen water must, therefore, be kept in small phials, quite full and closely stopped. 

Both the preceding compounds, when pure, are colourless and their solution, mixed with acids, gives off sulphuretted hydrogen, without the deposition of sulphur. By keeping, however, they become yellow, and acids cause a precipitation of sulphur. This is owing to the formation of persulphuret of ammonium. 

This acid is formed when selenium is oxidised by fusion with nitre. The fused mass is dissolved in water, and the selenic acid precipitated as seleniate of lead by adding a salt of lead. The seleniate of lead is decomposed by sulphuretted hydrogen, and the filtered solution of selenic acid cautiously evaporated till it has the Sp. G. 2 625. It is now hydrated selenic acid, HO, SeO, or rather H, SeO. It is very acid and corrosive, and resembles sulphuric acid very much. It may be recognised by the action of hydrochloric acid, which reduces it to selenious acid, chlorine being set free. Selenic acid is not decomposed by sulphurous acid (as selenious acid is), or by sulphuretted hydrogen. It produces intense heat when mixed vsdth water. 

Boron, when heated in the vapour of sulphur, bums and forms a sulphuret of boron, which is a white solid decomposed by water, with which it yields sulphuretted hydrogen and boracic acid. 

Heated with sulphur, silicon combines with it, forming a white, earthy compound. Si S,. It decomposes water, yielding sulphuretted hydrogen and silicic acid SiS, 4-3HO = 3HS + SiO,. 

Protosulphuret of potassium is a solid of a bright red colour, which forms with water a colourless solution. This solution smells of sulphuretted hydrogen, and probably contains that compound and potash, formed by the action of water on the sulphuret. KS -f- HO = KO - - HS. The solution is alkaline, and if pure is decomposed by acids, without any separation of sulphur, sulphuretted hydrogen being given off. 

This compound is found native. It may be formed by passing a current of sulphuretted hydrogen over sulphate of manganese at a red-heat. The sulphuric acid of the sulphate is expelled, and the protoxide is acted on by the sulphuretted... 

This also occurs in natnre, and is attracted by the magnet. It dissolves in acids, yielding sulphuretted hydrogen and a residue of sulphur. 

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