A manual of practical chemistry for public health students : especially arranged for those studying for the D.P.H / by A.W. Stewart.

  • Alfred Walter Stewart
Date:
1913
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Licence: In copyright

Credit: A manual of practical chemistry for public health students : especially arranged for those studying for the D.P.H / by A.W. Stewart. Source: Wellcome Collection.

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    of oxalic acid (COOH)2. 2H20 ; 1-965 grm. C02 are equivalent to 126 Xl'^5 = 5-6442 grm. oxalic acid.] Use phenolphthalein as indicator. As there is no C02 present we can use this indicator. Barium carbonate, being heavy, settles in the hollow stopper when the bottle has been inverted long enough. The baryta water in the bottle absorbs the C02 and forms BaC03. After sufficient time invert the bottle and allow the precipitate to settle for ten minutes. From the hollow stopper pipette out 25 c.c. of clear liquid, place in a flask, add phenolphthalein and from a burette run in standard oxalic acid solution till the pink colour is dis- charged. Double the titration of the latter. Example :— 50 c.c. Ba(OH)2 blank experiment = 34-7 c.c. oxalic acid. 50 ,, ,, experiment = 32-4 ,, ,, Difference = 2-3 c.c. oxalic acid = 2-3 c.c. C02. Volume of water = 2910-50 c.c. for Ba(OH)2 = 2860. Pressure, 757 mm. Temp., 15-5° C. According to Boyle’s law the volume of gas varies inversely as the pressure, and according to Charles’ law a gas increases by of its bulk at o° C. for every degree increase in temperature. Expressing the result at N.T.P. (760 mm. and at o° C.), as 1 c.c. of the oxalic acid solution = 1 c.c. of CO„ at N.T.P. v x P x = V3P3 6X dr. Vj = 2910-50 = 2860 Px = 757 mm. 6X = t 4- T, i.e., 15-5° + 2730 = 288-5 d2 = T, i.e., 273 P„ = 760 Whence V2 = = 2695-6 c.c. In 2695-6 c.c. air there are 2 3 c.c. CO„ 100 c.c. „ „ 2-^T = -o85 % at N.T.P. Expressing the result at the temperature and pres- sure of experiment.—Volume of C02 observed at I5'5° C. (and at 757 mm. in volume of air 2860) = 2-3 x fff x (1 + Vrl) = 2-4 c.c. In 2,860 c.c. air there are 2-4 c.c. C02 ; in 100 c.c. air there are 2 42g6oIO° = -084 per cent, at temperature and pressure of experiment.