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.

716/796 (page 690)

$charcoal, and then through a mixture of CaOAq and KOHAq. Properties.—A colourless, tasteless, slightly odorous gas; liquefied at low temperature and great pressure (v. supra). CO is combustible but a non-supporter of combustion : the tem- perature of the flame of CO in air is about 1400J (Valerius, J. 1874. 58). Absorbed by C, and by several metals, e.g. K, Ag, Au; quickly absorbed by Cu,Cl, in a little HOAq (v. infra) ; decomposed at very high temperature to C and CO;,; decomposed when moist by induction- sparks ; CO is an energetic reducer; it combines with moist KOH (or NaOH) to form K formate ; combines directly with CI and Br in sunlight. CO is extremely poisonous ; it removes 0 from the blood and combines with the haemoglobin. CO may be detected in the blood by observing the absorption-spectrum ; this is almost identi- cal with that of oxygenated blood, and is charac- terised by two bands between D and E ; on add- ing a little ammonium sulphide these bands dis- appear in the case of oxygenated blood, and the spectrum shows one band midway between D and E ; if the blood contains CO the two bands remain unchanged for several days (Vogel, B. 11, 235 ; Hoppe-Seyler, Fr. 3, 439). Reactions.—1. Electric sparks cause a partial decomposition to CO, and C ; if the CO., is re- moved the change proceeds (Berthelot, A. Ch. [5] 30, 547). According to Berthelot (Bl. [2] 21, 102 ; A. Ch. [5] 17, 142) CO is decomposed by the induction-discharge, with production of CO, .and (?) C40:1 and C504 (v. ante ; beginning of this art.). According to Buff a. Hofmann (C. J. 12, 282) the induction-spark does not decompose dry pure CO. Dixon (C. J. 49, 103) found that CO was decomposed (only about \ p.c. of the total gas)by sparks from aLeyden jar.—2.Heated to about 1300° CO is partially decomposed to C and C02 (Deville, C. R. 59, 873).—3. A mixture of CO with oxygen is burnt to C02 by applica- tion of a flame or electric sparks. Dixon (T. 1884'. 617) has proved that if both gases are perfectly dry no chemical change occurs when a spark is passed; that a mere trace of steam renders the mixture explosive ; that the oxida- tion of CO by O takes place very slowly if only a very small quantity of steam is present; and that as the quantity of steam is increased the rapidity of the explosion is increased also. The steam acts as a carrier of O to the CO ; it is probably reduced, and the H is then again oxidised : the reactions which occur are very probably these (v. Dixon, C. J. 49, 94): (2CO + 2H..0 = 2C02 + 2H21 12112 + 02 = 2^0 J ' Or (Armstrong, C. J. 49, 112) the changes may be represented by the formula?, before explosion O.H,O.CO; after explosion OH,.OCO. Small quantities of gases other than H20 were tried (H,S, C,H„ H,CO„ NH3, C5H„, HC1; S02, CS2, CO.,, N,0, C,N,, CCLJ ; if the'gas contained H, explosion occurred; if the gas did not contain H the mixture did not explode.—4. When a mixture of CO and steam is heated to about 600°, a portion of the CO is oxidised to C02; the amount of CO oxidised depends on the con- ditions (v. Dixon, C. J. 49, 94: references to other memoirs are given); if the C02 is removed as it is formed the whole of the CO can be oxidised. L. Meyer's experiments (B. 19, 1099), however, seem to prove that a mixture of dry CO and O can be exploded if a very strong spark is used, and the temperature is thus made very high. The gases must be under consider- able pressure; the more dilute the gaseous mixture the more difficult is it to explode it. —5. When sparks from an induction-coil are passed through a mixture of CO and steam, C02, a little formic acid, and in some cases C, are formed (Dixon, C. J. 49, 94).—6. When to a mixture of dry CO with hydrogen, oxygen in- sufficient for complete combustion is added, and the mixture is exploded by the spark, CO, and H,0 are formed; the ratio of C02 to H,0 depends on the shape of the vessel, and the pressure up to a certain limit; above this pressure — the ' critical pressure '—the ratio C02:H,0 is independent of the shape of the vessel. The larger the quantity of O used the lower is the critical pressure. So long as the volume of H is more than twice that of the O the ratio of CO x H,0:CO, x H, remains constant, provided no H,0 can condense, and the pressure is above the critical pressure: when the vol. of H is less than twice that of O the value of the ratio diminishes. The presence of an inert gas, e.g. N, increases the formation of CO, and diminishes that of H„0, hence it lowers the value of the ratio CO x H,0:C02 x H2. This ratio is called by Dixon the co-efficient of affinity of the reaction (v. Dixon, T. 1884. 617; C. J. 49, 94; Horst- mann, B. 12, 64 ; v. also Chemical change).—7. CO is oxidised to CO, (1) by bichrome and sul- phuric acid (Ludvig, J. 1872. 248); (2) by palla- dium charged with hydrogen, in presence of oxygen and water, H20.2 being also produced (Traube, B. 15, 2325, 2854; 16, 123; Kemsen a. Keiser, B. 17, 83); (3) by mixing with oxygen and passing over platinum-black; (4) by nitro- gen dioxide [NO,] (Hasenbach, J. pr. [2] 4, 1); (5) by heating with most metallic oxides ; (6) by heating with many oxysalts, e.g. alkaline sul- phates (sulphides produced).—8. Many experi- ments have been made to determine whether CO is oxidised by contact with moist oxygen in presence of slowly oxidising phosplwrus; the balance of evidence seems to show that C02 is not produced (Remsen (and others) Am. S. [3] 11, 316; B. 17, 83 ; Am. 6, 153 ; Leeds, B. 12, 1836 ; C. N. 48, 25 ; Baumann, B. 16, 2146; 17, 283).—9. CO reacts with moist potash or soda to form alkali formate (Berthelot, A. Ch. [3] 61, 463); the reaction proceeds most quickly at 190°-200°, and is best accomplished by leading moist CO over soda-lime (Frohlich a. Geuther, A. 202, 317).—10. With ferrous oxide at 300°^400°, CO, and a little C are formed (Griiner, C. R. 73, 281).—11. CO appears to react with certain metallic peroxides to form carbonates, but, according to Wright a. Luff (C. 33, 540), C02 is formed by partial reduction of the per- oxide and reacts with the lower oxide to produce carbonate.—12. Many of the preceding reactions exhibit CO as a reducing agent; it also reduces PdCl.Aq to Pd.—13. When sodium or potassium is heated to redness in CO, alkali carbonate and C are formed. Combinations.— 1. With potassium at about 80° to form the explosive compound KCO (Brodie, C. J. [2] 12, 269), v. Potassium.—$