Estimation of Methane

Since there is no known absorbent for methane, this gas is estimated in a gaseous mixture by burning it, and determining the amount of carbon dioxide produced either (a) volumetrically or (b) gravimetrically.

1. To estimate the carbon dioxide volumetrically a given volume of gas is exploded with excess of air, and the volume after explosion noted. The residual gas is then shaken with caustic potash, and the diminution of volume thus brought about is that of the carbon dioxide, which is equal to the volume of methane originally present. If the methane was mixed with hydrogen the volume of the hydrogen is estimated by the following formula:
   
   If x - contraction after explosion
   
   and y = contraction after exposure to potash = volume of methane, volume of hydrogen = 2/3(x - 2y).
   
   According to Bone and Coward small percentages of methane in presence of large excess of hydrogen cannot be accurately estimated by explosion. The hydrogen may, however, be previously removed and estimated by absorption in contact with palladium, and also by fractional combustion if the mixed gases containing excess of oxygen are passed over palladium sponge or palladium asbestos at 100° C., since at this temperature the hydrogen burns, but not the methane.
2. The carbon dioxide formed by the combustion of methane may be estimated gravimetrically after the manner of ultimate organic analysis by passing the methane through a tube containing red-hot copper oxide, and absorbing the resulting carbon dioxide in weighed potash bulbs after removing the water by calcium chloride.