Volume 1

Watts' dictionary of chemistry / revised and entirely rewritten by H. Forster Morley and M.M. Pattison Muir ; assisted by eminent contributors.

Date:: 1888-1894

Credit: Watts' dictionary of chemistry / revised and entirely rewritten by H. Forster Morley and M.M. Pattison Muir ; assisted by eminent contributors. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

721/796 (page 695)

$alcoholic potash. A very delicate reaction is to bring the CS2 into contact with PEt3 when a characteristic carmine-red compound, PEt,.CS,, forms ; it may be crystallised from ether. This reaction may also be applied for the estimation of CS, (Hofmann, B. 13, 1732). CS, is some- times determined, e.g. in xanthates, by standard- ised CuSO,Aq (Grete, B. 9, 921); thiocarbonates may be converted into the Pb salt (by addition of Pb acetate), and this may be decomposed by boiling with water, and the CS, led into weighed bulbs containing alcoholic potash (Delachanal a. Mermet, B. 8, 1192). Carbon, sulphochlorides of. I. Thio-carbonyl chloride. CSC1.,. Mol. w. 114-69. (70°). V.D. 57-5. Formation.—1. By reaction between CI and CS.,.—2. By heating CCl, with S.—3. By passing CCl., and H .S through a hot tube (Kolbe, A. 45,41; Carius, A'. 113, 193; Miiller, C. J. 15, 41; Gustavson, B. 3, 989). Preparation—To dry CS, about -2 p.c. I is added and dry CI is passed in (a reversed con- denser being attached) until the volume of liquid has increased by about ^. The whole is boiled with water (to remove S,CL); separated S is removed, water is separated, the liquid is distilled from the water-bath whereby CCl, and CS, distil over ; the residue is then distilled till a thermometer in the liquid reaches 175° ; the distillate is fractionated, digested with water to remove S,CL, dried, and fractionated. About 320 g. CSC1, (v. infra) are thus obtained from 1 kilo. CS,; very finely divided silver (by reducing AgCl) is then added little by little (the liquid being kept cold) until the whole of the liquid is soaked into the silver; it is then distilled, the distillate is shaken with water to remove traces of S,CL, dried, and fractionated (Ratlike, B. 3, 858). The reactions are (1) 2CS, + 5C1„ = 2CSC1,, + S,,CL; (2) CSCL, + 2Ag = 2AgCl + CSCL. Properties and Reactions.—Golden-red, lim- pid, liquid; penetrating odour, resembling that of COCL; fumes in air. Exposed to light and then to a low temperature, large colourless crystals of a polymeride, nCSCL, separate; this body is unchanged in air; melts at 112-5° ; is volatilised in steam; at 180° in a closed tube it gives CSCL. II. Thionyl perchloride. CSC1., (Rathke, B. 3, 858). Prepared by action of CI on CS, (v. Thionvl chloride, Preparation). A clear, golden-yellow liquid ; vapour causes free flow of tears; B.P. 146°-147°; S.G. 1-712 at 12-8°. De- composed, slowly by moist air, quickly by heat- ing with water to 160°, to CO,,, HClAq, and S. Heated to 200° is decomposed to CC1„ S,CL,and a little CSCL. M. M. P. M. CARBONATES v. Carbonic acid, Carbonates, and Thio-carbonates. CARBON TETRA-BROMIDE v. Tetra-bromo- methane. DI-CARBON-TETRA-CARBOXYLIC ACID v. Ethylene-tetra-carboxylic acid. CARBONIC ACID, CARBONATES, AND THIO-CARBONATES. Carbonic acid. A solution of CO., in water probably contains carbonic acid, H\C03. The chief reasons for this statement are as follows. The mass of C02 dissolved by water at ordinary temperatures and small pressures (less than 760 mm.) varies as the pressure. But at pres- sures of 2, 3, or more atmospheres, the mass of C02 dissolved is less than that calculated by the law of Henry a. Dalton. Khanikoff a. Longui- nine (A. Ch. [4] 11, 412) give these numbers:— P = pressure in mm., o = vol. of C02 (measured at 0° and 760 mm.) dissolved by 1 vol. water at about 15°. P. a. P. a. 697-71 0-9441 2188-65 3-1764 809-03 1-1619 2369 02 3-4857 1289-41 1-8647 2554-0 3 7152 1469-95 2-1623 2738-33 4-0031 2002-06 2-9076 3109-51 4-5006 When the pressure is decreased to 760 mm. over water saturated with C02 at pressures greater than 760 mm. most of the CO,, escapes, at first rapidly, then slowly; the last traces of C02 can be removed by placing the water in vacuo, or by long-continued boiling. Magnesium reacts with a solution in water of C02 to form MgCO:! and H; the quantity of H evolved is almost exactly that calculated on the hypothesis that the re- action is H,CO.,Aq + Mg = MgCO., + H, (Ballo, B. 15, 3003). Water holding in solution Na,CO:j or K,,CO:! dissolves considerably more CO,, than pure water ; NaHCO, (or KHCO:() is produced (Ballo, I.e.). Mg reacts with aqueous solutions of NaHCO., or KHCO:i to form MgCO:j, K, (or Na,)CO.„ and H (Ballo, I.e.). Aqueous solu- tion of CO., turns blue litmus wine-red, the blue colour returns on exposure to air; blue litmus in contact with CO,, at pressures of 1} to 2 atmospheres becomes vermilion-red (Malaguti, A. Ch. [3] 37, 200). When CO., dissolves in water, heat is produced; [CO-,Aq] = 5,880 (Th. 1, 260). This solution reacts thermally with alkalis as a dibasic acid; thus (Thomsen)— n [CO'-Aq,»NaOHAq] 1 11,016 2 20,084 The thermal value of the second formula-weight of NaOH (9,068) is considerably less than that of the first (11,016); in this respect carbonic acid behaves like sulphurous, selenious, boric, acid, &c. (v. Acids, basicity op). When moist C02 reacts with KOH, K,,C03 is obtained; from this a great many carbonates may be formed, the composition of which is that of metallic derivatives of a dibasic acid H,C03. The aqueous solutions of carbonates are decom- posed by almost all acids, not by HCNAq or H B,0.,Aq; hence the affinity of carbonic acid is small (v. Affinity). But soluble silicates are at once decomposed by CO.Aq, and even in- soluble silicates e.g. of Ca, Al, &o. are slowly decomposed by moist C02. The sulphur ana- logue of carbonic acid—H,CS3— has been iso- lated. Finally various derivatives, both of CO(OH)., and CS(SH), are known; viz. COCL, (?COBr„), CO(NH,).„ COS, CSCL, CS.NH...SH, CS(NH,),. Carbonates. Normal carbonates have the composition M2C03 or MCO.,. Certain acid car- bonates, MHC03, have also been isolated; very few of these are known as delinite solids, the principal are when M = Na, K, NH4 (? Tl). Some insoluble normal carbonates, e.g. Ba, Mg, Ee, dissolve in water saturated with CO,; at a$