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
Licence: Public Domain Mark
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.
682/796 (page 656)
![Cadmium, Hydroxide of, Cd02H2. A white, amorphous solid, obtained by adding KOHAq to a dilute aqueous solution of a Cd salt, wash- ing with warm water, and drying at 100°-200° (Schaffner, A. 51, 168). According to Nickles (J. Ph. [3] 12, 406) CdO,H2 is obtained in crys- tals by keeping Cd in contact with Fe in NH3Aq. De Schulten (C. B. 102, 72) describes the formation of hexagonal crystals of CdO.,H.„ S.G. ±±° 4-79, by dissolving 10 grams CdL, in 150 c.c. H,0 mixed with 360 grams KOH contain- ing 13 p.c. H,0, heating till all is dissolved, and cooling. Thomsen gives the thermal value [Cd,0,H-'0] = 65,680 ; and the following values for the heat of neutralisation of solid Cd02H2 (Th. 3, 285) : Q [M,QAq] H.,SO., 24,200 h.;n2os 20,620 H2S20„ 20,360 H.,C12 20,290 HJSr2 21,560 H2I2 24,210 M = Cd02H2. The quantity of heat produced with the three haloid acids increases as the atomic weight of the halogen increases; in this respect Cd02H2 is analogous to the corresponding compounds of Hg and Pb, and differs from those of Ba, Ca, Sr, and Mg. CdOJB, loses H.,0 at 300° (H. Kose, P. 20,152) ; Cd'O is not hydrated by contact with H,0; according to the thermal values given by Thomsen (Th. 3,285; and P. 143,354 a. 497) the reaction CdO + H20 = CdO,H, would require the expenditure of about 10,000 units of heat. Cadmium, Iodide of. Cdl2. Mol. w. un- known, but probably as represented by the formula. [404°] (Carnelley, C. J. 33, 278). (708°-719°, with decomposition) (Carnelley a. Williams, C. J. 37, 126). S.G. 5-644, and 4-626 (v. Preparation a. Properties). H.F. [Cd,F] =48,830; [Cd,P,Aq] = 47,870 (Thomsen). V, = V0 (l + -00008748<), t not greater than 40° (Fizeau, C. B. 64, 314). S. (20°) 92-6; (60°) 107-6 ; (100°) 133-3 (Kremers, P. 103, 57 ; 104, 133; 111, 60). Preparation and Properties.—1. By heating together Cd and I, in the ratio Cd:I2, in absence of air.—2. By digesting together Cd and I under water (Stromeyer, S. 22, 362).—3. By evapora- ting a solution of 20 parts KI and 15 parts CdSO., to dryness, dissolving in alcohol, and crystalli- sing (Vogel, N. B. P. 12, 393).—4. By dissolving CdC03 in HIAq, decolourising by addition of clippings of Cd, and crystallising (Clarke, Am. 5, No. 4).—5. By dissolving Cd in HIAq, evapo- rating, and crystallising (Clarke, I.e.). Accord- ing to Clarke (I.e.) Cdl2 exists in two forms ; the normal salt is white, is unchanged by heating to 250°, and has S.G. 5-644; the other salt is brownish, loses weight even at 40°, and has S.G. 4-626. The conditions under which the less stable salt is formed have not yet been exactly determined ; Clarke obtained it twice, by the action of HIAq on Cd and on CdC03. The S.G. of the less stable salt increases by heating to 50° for some time. If the formula- weight Cdl2 is divided by the S.G., the results are, for the stabler salt 64-8, and for the less stable salt 79-2; now S.V.S. of Cd + S.V.S. of I2 = 64-3 (Clarke, I.e.). Combinations.—1. With ammonia to form CdI2.6NH3 and CdI,.2NH3 ; obtained as the corresponding CdCl2 compounds (q. v.): both are decomposed by H20 with ppn. of Cd02H2 (Ram- melsberg, P. 48, 153).—2. With some metallic iodides to form double salts; Croft (J. pr. 68, 399) described CdI2.2KI.2H20 (aqueous solution of this salt pps. most of the organic bases from plants; Marme, N. B. P. 16, 306); CdI,.2NH ,I.2H.,0 ; CdI.,.2NaI.6H.,0 ; CdI..BaI2.5H20; and CdI2.SrI,.8H20. Clarke (Am. 5, No. 4) obtained CdI2~3HgI2 as gold- coloured plates. Cadmium, Oxide of. CdO. Mol. w. unknown. S.G. (amorphous) 6-95, (crystalline) 8-11 (Stro- meyer, S. 22, 362; Werther, J. pr. 55, 118; Schuler, A. 87, 34; Sidot, C. B. 69, 201; Fol- lenius, Fr. 13, 279). H.F. [Cd,0] =75,500 (cal- culated from data given by Thomsen, Th. 3, 285 ; P. 143, 354 a. 497). Preparation.—As a dark-brown, amorphous, infusible, powder, by burning Cd in air or O ; or by strongly heating Cd02H2, or CdC03. As black-brown very small octahedra (or other forms of the monometric system), by strongly heating Cd.2N03, or CdSO,, (Werther, I.e.; Schil- ler, I.e.; Herapath, B. J. 3, 109). Properties &e.—Reduced to Cd by heating with C. At red heat CI forms CdCL. Readily combines with C02 forming CdC03. Dissolves in aqueous acid with production of Cd salts. Thomsen (P. 143, 354 a. 497) gives the thermal values, [CdO,H-SOAqJ = 14,240 for crystalline CdO, and 14,510 for amorphous CdO. Marchand (P. 38, 145) supposed that a lower oxide than CdO was formed when CdC20, was heated; but Vogel's experiments (J. 1855. 390) seem to prove that the substance was a mixture, in varying proportions, of CdO and Cd. By the action of H20,Aq (about 3 p.c. H.,0.,) on moist Cd02H21 Haas (B. 17, 2249) obtained an oxide of Cd containing more O than CdO. Analyses gave results agreeing fairly with the formula Cd305, in one case with Cd40;. These results were confirmed by Bailey (C. J. 49, 484) who obtained Cd305 by the action of H20.,Aq on CdS04Aq followed by addition of NH3Aq. The pp. obtained by these methods may have been a mixture, or possibly a loose compound, of CdO and Cd02 (v. Haas, I.e. 2255). Cadmium, Phosphides of. Cd and P are said to combine when heated together to form a grey, slightly metal-like, mass, which burns in air to phosphates, and dissolves in HClAq with evolution of PH3 (Stromeyer, S. 22, 362). According to B. Renault (C. B. 76, 283) when P vapour is passed over hot Cd, two phosphides are formed, Cd.,P2 and Cd2P. Oppenheim (B. 5, 979) describes Cd3P2 as a grey, metal-like, crys- talline substance, produced by heating CdO with KOHAq and P, and heating in H. Cadmium, Salts of. Compounds obtained by replacing the H of acids by Cd. The Cd salts form one series CdX2, when X2=C12, (N03)2, (C103)2, S04, C03, HP03, &c. The V.D. of one salt, CdBr2, has been determined; from this result, and from the similarities between the salts of Cd and Zn, it is probable that the gaseous molecules of the haloid Cd salts are](https://iiif.wellcomecollection.org/image/b21995990_0001_0682.jp2/full/800%2C/0/default.jpg)
