Water with sodium carbide

Potassium cyanide, KCN.—The cyanide is manufactured by methods similar to those employed for the corresponding sodium derivative. Potassium ferrocyanide is heated either in absence of air, or with potassium carbonate and charcoal, or with sodium, the potassium cyanide being extracted by lixiviation with water or dilute alcohol. It is also obtained by the action of a mixture of steam and nitrogen on potassium carbonate or carbide,7 the manufacture of cyanides by the aid of atmospheric nitrogen being now an important industrial process. 

From the sulfuric acid solution, thorium may also be obtained by precipitation with sodium fluosilicate, sodium hypo-phosphate,1 or sodium pyrophosphate.2 An ingenious method for removing the phosphorus has been proposed by Basker-ville3 and used on a large scale. It consists in heating in an electric furnace a mixture of monazite, coke, lime, and feldspar. The phosphorus is distilled out and the mass allowed to cool. When extracted with water, acetylene is evolved from the calcium carbide formed during the heating, and the remainder crumbles to a fine powder. This is dissolved in hydrochloric acid, and the cerium earths removed. 

Figure 5.3 illustrates a process to manufacture acetylene from calcium carbide. The carbide is introduced by a screw conveyor into a perforated horizontal cylinder housed in a concentric envelope. Water is sprayed inside the internal shell. The acetylene formed passes upstream through the screw conveyor to a scrubbing tower, where, a new water spray carries off most, of the solids conveyed by the gas. The residual lime and carbide impurities are removed by a screw conveyor to a sludge receiver. The acetylene is cooled to — 10°C to condense most of the water. It is then purified by contact with dilute sulfuric acid in a liquid liquid absorber, and then with sodium hypochlorite prepared by the action of chlorine on caustic soda, to. remove impurities. The acetylene is then cooled to 0°C for the more complete separation of moisture. The final product nevertheless still contains 0.4 per cent by weight of water, which is suitable for most uses. More intensive dehydratation can be achieved by passage over silicagel. 

EXPLOSION and FIRE CONCERNS noncombustible slightly volatile at ordinary temperatures NFPA rating (not rated) may explode on contact with 3-bromopropyne, ethylene oxide, lithium, peroxyfonnic acid, and chlorine dioxide vapor ignites on contact with boron diiodophosphide reacts violently with acetylenic compounds, metals, chlorine, chlorine dioxide, methyl azide, and nitromethane incompatible with acetylene, ammonia, chlorine dioxide, azides, calcium, sodium carbide, lithium, rubidium, and copper heating to decomposition emits toxic fumes of Hg use water spray, fog, or foam for firefighting purposes. 

EXPLOSION and FIRE CONCERNS combustible solid NFPA rating (NA) reacts to form explosive products with metal amides contact with acids may cause formation of poisonous hydrogen selenide gas incompatible or reacts violently with barium carbide, bromine pen-tafluoride, chromic oxide, fluorine, lithium carbide, lithium silicon, metals, nickel, sodium, nitric acid, nitrogen trichloride, oxygen, potassium, potassium bromate, rubidium carbide, zinc, silver bromate, uranium, strontium carbide, and thorium carbide toxic gases and vapors may be released in a fire involving selenium, sodium selenite, sodium selenate, and selenium dioxide use water for firefighting purposes. 

EXPLOSION and FIRE CONCERNS not combustible NFPA rating Heath 3, Flammability 0, Reactivity 0 nonflammable gas reacts violently with acrolein, aluminum, cesium oxide, chlorates, chromium, manganese, potassium chlorate, sodium, sodium carbide, stannous oxide, fluorine, cesium acetylene carbide, and potassium acetylene earbide reacts with water or steam to produce toxic and corrosive fumes incompatible with halogens, lithium nitrate, metal acetylides, metals, metal oxides, polymeric tubing, potassium chlorate, and sodium hydride use water spray or suitable agent for firefighting purposes. 

Properties Yel. fuming liq. dec. in water (reactive) m.w. 221.90 dens. 3.189 m.p. 9.4 C b.p. 98 C Toxicology ACGIH TLV/TWA 2.5 mg(F)/m (air) poison toxic by ing., inh., and skin contact corrosive to skin and mucous membranes causes severe burns TSCA listed Precaution Oxidizer dangerous fire risk attacks glass reacts violently with water, potassium hydroxide explosive reaction with benzene (> 50 C), potassium, molten sodium incandescent reaction with calcium carbide, metals, nonmetals... 

One of the ways to dispose of chemicals that are reactive with water is hydrolysis, that is, the reaction with water under controlled conditions. Inorganic chemicals that can be treated by hydrolysis include metals that react with water metal carbides, hydrides, amides, alkoxides, and halides and nonmetal oxyhalides and sulfides. An example of a waste chemical treated by hydrolysis is the reaction with water of sodium aluminum hydride (used as a reducing agent in organic chemical reactions) ... 

Ionic carbides react with water, forming acetylene. For example, sodium carbide reacts with water according to the reaction shown here ... 

Drying agents may be divided broadly into (a) those which combine with water reversibly and (6) tho.se which react chemically with water by a non-revcrsible process giving rise to a new water-free compound. Sodium, calcium carbide and phosphorus peiitoxide belong to the latter class and wih be discussed in Section 11,39. 

The usual extraction procedure is to roast the crushed ore, or vanadium residue, with NaCl or Na2C03 at 850°C. This produces sodium vanadate, NaV03, which is leached out with water. Acidification with sulfuric acid to pH 2-3 precipitates red cake , a polyvanadate which, on fusing at 700°C, gives a black, technical grade vanadium pentoxide. Reduction is then necessary to obtain the metal, but, since about 80% of vanadium produced is used as an additive to steel, it is usual to effect the reduction in an electric furnace in the presence of iron or iron ore to produce ferrovanadium, which can then be used without further refinement. Carbon was formerly used as the reductant, but it is difficult to avoid the formation of an intractable carbide, and so it has been superseded by aluminium or, more commonly, ferrosilicon (p. 330) in which case lime is also added to remove the silica as a slag of calcium silicate. If pure vanadium metal is required it can... 

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