The oxygen test set can also be used as a nitrogen test set by using stick phosphorous in place of copper wire and water in place of Ammonium Chloride solution. Yellow or white phosphorous submerged in water is used for absorbing the oxygen (which is principle impurity in the nitrogen gas) to form phosphorous pent oxide, which is soluble in water. The volume of remaining gas nitrogen is then measured in the burette. A downward graduated burette may be used for easy reading.
It is dangerous to pass gas containing more than 7% oxygen into the phosphorus test set. Phosphorus is highly combustible when exposed to air. Always keep it completely immersed in water both in the test set and in storage. Use tongs when handling phosphorus. Do not handle with the fingers.
PREPARATION OF THE TEST SET:
Invert the reaction chamber, remove the rubber cork 'F' pinch the rubber tube to close it and fill the chamber and the reservoir with water. Using tong fill the chamber with 3/16 or ¼ inch diameter stick phosphorus.
Cork the reaction chamber and connect the chamber to the stop cock 'H' Fill the leveling bottle and the purging vessel half with water. Turn the stop-cock to connect the reaction chamber with the burette and lower the leveling bottle. The water from the reservoir will rise in the reaction chamber and will flow down in the burette through stop-cock 'H' then turn the stop cock 'H' to open to the purging vessel, at the same time, turn open cock 'G' also. Raise the leveling bottle so that water will raise through the burette, cock 'H', the rubber tube connection and the cock 'G' and finally it will tickle down to the purging vessel. By raising and lowering the leveling bottle a few times, all the air present in the burette and the rubber tubing connections including the cocks 'G' & 'H' should be expelled. After checking for air bubbles in the chamber and the burette, close the clock 'H' and turn open the cock 'G' for sample gas connection. The sample gas to be tested in allowed to bubble through water to atmosphere.