Modern Gasworks Practice

CONTROL OF HORIZONTAL RETORT SETTINGS 131 Instructions for Using the Wright-Orsat Apparatus Preliminary. 1. Fill the water-jacket surrounding the measuring burette with water. This water is simply employed to equalize the temperature of the gas. 2. Fill the aspirator with. water, preferably saturated with the gas, to be analysed. 3. The first pipette is half filled with a solution of caustic potash. To do this the burette is filled with water from the aspirator by opening the 3-way cock at the end of the capillary tube connecting to air. The 3-way cock is tlien closed and the aspirator lowered, thus drawing the potash. into the pipette up the inner tube until it reaches the level of the india-rubber connection. When this is done, there should be about |-inch of liquid sealing the bottom of the inner tube of the potash pipette. The cock on the capillary tube attached. to this pipette is now closed. 4. The above manipulation is repeated with the other pipettes on the apparatus, the second one being filled with. alkaline solution of pyrogallic acid for absorbing the oxygen, and the third with a solution of cuprous chloride for absorbing the carbon monoxide. The pipe conveying the gas to be analysed is attached to the bottom of the filter tube containing cotton-wool as shown by the arrow in Fig. 67. The rubber pump is attached to the free end of the 3-way cock at the end of the capillary and the cock is turned so that, by operating the hånd pump, the pipes are cleared of the stale gas and a supply of new gas for analysis is brought right up to the instrument. The 3-way cock is then turned the other way and the aspirator lowered so as to draw a supply of gas through, the cotton-wool filter tube into the burette. With a little care it is easy to arrange the liquid surfaces in the burette and the aspirator so that they are level and the volume of gas in the burette is at the bottom graduation 0. When this has been done, the cock connecting to the first pipette, i.e., the potash. pipette, is turned, and the gas is passed to and fro from the burette into the pipette, care being taken not to draw the liquid from the potash pipette higher than the rubber connection. After performing this manipulation two or three times, the gas is drawn back into the burette until the liquid in the potash. pipette just reaches the rubber connec-tion. The liquid surfaces in the aspirator and burette are th.en levelied as before. The new reading of the gaseous volume is observed. The contraction gives the amount of carbon dioxide in the gas. This manipulation, is repeated with the ■second and third pipettes, thus obtaining the amount of oxygen and the amount of carbon monoxide. Carbon dioxide is always the first gas to be removed from a gaseous mixture. It is important to use the reagents in the order given. If, by mistake, the gas is passed into the second pipette, it will absorb not only oxygen, for wliich it is intended, but also carbon, dioxide. Similarly, if the gas be passed into the third pipette, it will absorb not only carbon monoxide, but also oxygen, as well. Glass stop-cocks sh.ou.ld always be treated with a little vaseline when used in connection with vessels containing caustic potash.