A handy method of determining the amount of carbonic acid in air / by William Mackie.

  • Mackie, William
Date:
1905
Catalogue details

Licence: In copyright

Credit: A handy method of determining the amount of carbonic acid in air / by William Mackie. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    Principle of the Method. The method depends on the theoretical view that equal quantities of alkali in solution, when they present equal surfaces for absorption and are of equal depth, will be neutralized by the CO2 iu a given atmosphere in equal times: and by implication that surface, depth and strength of solution being constant while other conditions vary, the times necessary for neutralization will be inversely as the amounts of CO^ present in the atmosphere to which they are exposed. Experiment shows that this is a very close approximation to the truth. To put the princi[)le in concrete form, it may be said that drops of alkaline solutions which are equal both as regards their diameters and the quantity of solution which they contain, whether of lime water, baryta, or magnesium hydrate, within the limits of strength indicated, if coloured by phenolphthalein, have their colour discharged in times which are practically in the inverse ratio of the amounts of CO2 present in the several atmospheres to which they are exposed—that is to say, if one atmosphere contains twice as much as another it will decolorize equal-sized spots of these solutions, coloured as indicated, practically in half the time ; if it contains three times as much it will decolorize them practically in one-third the time, and so on. If the diameters of the spots are unequal while the quantity of solution in the spots remains constant, the times of decolorization for the same atmosphere are inversely as the square of the diameters of the several spots, that is to say, inversely as their surfaces. This has been found from experimental data to hold good at least within the limits of experimental error. The method therefore is simply this:—A number of as nearly as ^ possible equal spots of one or other of these solutions, coloured as indicated, is exposed on a white surface to the atmosphere in which ..| it is proposed to estimate the CO2, and the time required for complete discharge of their colour noted. The CO2 present in vols. in 10,000 parts is a function of the strength of the solution used, divided by the time in minutes taken for the discharge of the colour. Stated generally the formula is:— v' ?-^^=vols. of COa in 10,000 parts, ^ K where s is the strength of the solution stated in particular terms, i / is a factor which within the range of experimental error is § fairly constant, 9 X is the time of colour discharge in minutes. 8
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