Ammonia—ammonium thiocyanate mixtures

A—B—A block copolymers assessment of samples, 23—24 construction of phase diagrams, 24 light-scattering measurements, 24—25 preparation of samples, 23 Adsorbed polymer layer around a sphere, self-similar picture, 32132 323 Ammonia—ammonium thiocyanate mixtures, solvents for cellulose, 157 Amphiphilic lipopeptides advantages, 117... 

LEAD DINITRATE (10099-74-8) Pb(N03)2 Noncombustible solid. A strong oxidizer accelerates burning of combustible materials. Violent reaction, or may form explosive materials, with reducing agents, including hydrides, nitrides, phosphoms, stannous chloride, and sulfides alkyl esters (forms explosive alkyl nitrates) combustible materials, potassium hexanitrocobalite(III) (C. I. pigment yellow), cyclopentadienyl sodium, red hot carbon, lead(II) phosphinate, phosphoms, tin(II) chloride. Incompatible with aluminum, ammonia, ammonium thiocyanate (mixture forms the shock- and friction sensitive explosive guanidine nitrate) citric acid, hydrozoic acid, metal phosphinates, methyl isocyanoacetate, sodium peroxyborate, potassium acetate. 

Only a few solvents are known to dissolve cellulose completely, and solid cellulose decomposes before melting. Therefore, it is difficult to study the mesophase behavior of cellulose. Chanzy et al. [32] reported lyotropic mesophases of cellulose in a mixture of jV-methyl-morpholine-Af-oxide and water (20-50%), but were unable to determine the nature of the mesophase. Lyotropic cholesteric mesophase formation in highly concentrated mixtures of cellulose in trifluoroa-cetic acid + chlorinated-alkane solvent [33] and in ammonia/ammonium thiocyanate solutions [34] has been studied, and although poor textures were obtained in the polarizing microscope, high optical rotatory power has been measured in an optical rotation (ORD) experiment, which could be fitted to the de Vries equation [Eq. (3)] for selective reflection beyond the visible wavelength region and was taken as proof of a lyotropic chiral nematic phase. 

Chemical Properties. Ammonium thiocyanate rearranges upon heating to an equiHbrium mixture with thiourea 30.3 wt % thiourea at 150°C, 25.3 wt % thiourea at 180°C (373,375). At 190—200°C, dry ammonium thiocyanate decomposes to hydrogen sulfide, ammonia, and carbon disulfide, leaving guanidine thiocyanate [56960-89-5] as a residue. Aqueous solutions of ammonium thiocyanate are weakly acidic a 5 wt % solution has a pH of 4—6. 

According to an O.S. amendment sheet, the procedure as described [1] is dangerous because the reaction mixture (dicyanodiamide and ammonium nitrate) is similar in composition to commercial blasting explosives. This probably also applies to similar earlier preparations [2]. An earlier procedure which involved heating ammonium thiocyanate, lead nitrate and ammonia demolished a 50 bar autoclave [3], TGA and DTA studies show that air is not involved in the thermal decomposition [4], Explosive properties of the nitrate are detailed [5], An improved process involves catalytic conversion at 90-200°C of a molten mixture of urea and ammonium nitrate to give 92% conversion (on urea) of guanidinium nitrate, recovered by crystallisation. Hazards of alternative processes are listed [6],... 

Procedure Weigh accurately about 0.3 g of ethionamide in a flask and dissolve in 10 ml of dilute sulphuric acid. Add to it 100 ml of water, 20 ml of dilute ammonia solution and rapidly 50 ml of 0.1 N silver nitrate solution. Allow the resulting mixture to stand for a few minutes, filter and wash the filter paper with three successive quantities, each of 10 ml of DW. To the combined filtrate and washings, add 60 ml of dilute nitric acid, cool and titrate with 0.1 N ammonium thiocyanate employing 5 ml of ferric ammonium sulphate solution as an indicator. Each ml of 0.1 N silver nitrate is equivalent to 0.008312 g of C8H1QN2S. 

The crude tetrachloride mixture of zirconium and hafnium is dissolved in ammonium thiocyanate solution. The solution is extracted with methyl isobutyl ketone (MIBK). MIBK is passed countercurrent to aqueous mixture of tetrachloride in the extraction column. Halhium is preferentially extracted into MIBK leaving zirconium in the aqueous phase. Simultaneously, zirconium tetrachloride oxidizes to zirconyl chloride, ZrOCb. When sulfuric acid is added to aqueous solution of zirconyl chloride, the chloride precipitates as a basic zirconium sulfate. On treatment with ammonia solution the basic sulfate is converted into zirconium hydroxide, Zr(OH)4. Zirconium hydroxide is washed, dried, and calcined to form zirconium oxide, Zr02. 

Ammonium nitrate prepared from ammonia obtained by the dry distillation of coal should not be used as component of any explosive material because of the ammonium thiocyanate and pyridine present in it (the latter as nitrate). When the ammonia liquor from dry distillation of coal was the sole source af ammonia and ammonium nitrate, decomposition of mixtures containing ammonium nitrate with TNT (amatols), was brought about at the melting point TNT reacted with ammonium thiocyanate or with pyridine nitrate and evolved gaseous products. Minute traces of these impurities were sufficient to cause abundant gas evolution to develop during the fusion, pouring, and cooling of amatol. 

The formula of carbon dioxide is C02, that of carbon disulphide CS2 and it is evident that an intermediate substance should exist of the formula COS. This substance is carbon oxysulphide. It is a gas, prepared by heating thiocyanic acid, HSCN, the ammonium salt of il which is produced when ammonia is passed through a mixture of carbon disulphide and alcohol CS2 + 2NHg.Alc = H2S + (NH4) SCN.Alc. On evaporation of the alcohol the ammonium thiocyanate crystallises out. This salt, distilled with sulphuric acid, yields in passing the acid HSCN, which, on account of the high temperature, reacts with water, forming ammonia (which yields ammonium sulphate with the sulphuric acid) and carbon oxysulphide, COS HSCN + H20 = NHS + COS. 

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