PRESSURE MEASUREMENTS OF CORROSIVE GASES. THE VAPOR PRESSURE OF NITROGEN PENTOXIDE.1
Journal of the American Chemical Society
The Transhence Number of Potassium Ion in Potassium Chloride Solutions a t 25 ' . 1 0 -0 I o 3162 0 496 Concentration Mean Transference range. concentrdtion number 0 . 5 -0.05 o.o5-0,005 0 . 1 -0.01 0.1581 0.03162 o.oi.581 0.498 0.496 0.494 Summary. The work o€ MacInnes and Parker on the activity values and trans-Ierence numbers of potassium chloride solutions is extended to one molal concentration. The potential of the normal calomel electrode is calculated t o be -0 2826 volt, agreeing quite
... lt, agreeing quite well with Lewis, Sebastian and Brighton's value (--Q 2824 volt), when corrected for the liquid junction potential between o . r and I .o N potassium chloride solutions. C4MBRIDGI3, MASS [GONTRIBUTION FROM THE FIXED NITROGEN RESEARCH LABORATORY. ] Pressure measurements of the higher oxides of nitrogen and nitric acid are difficult because these substances attack materials on which the chemist usually relies, including rubber tubing, mercury and stopcock grease. Since such measurements are necessary for the proper study of nitr0ge.n fixation processes, an apparatus made entirely of glass has been devised which is capable of measuring gas pressures conveniently and accurately over a wide range of conditions. With it the vapor pressure of nitrogen pentoxide has been determined. Further related researches are also in progress. Description of the Apparatus. Its unique feature consists of the glass diaphragm, movement of which makes or breaks an electrical circuit and permits balancing of an air pressure against the unknown pressure. The air pressure is read directly on a mercury manometer as shown. A small bulb of glass, with a thin end, is blown as shown in the first illustration. This is flattened by plunging the end into a flame, momentarily, ~vliile rotating. A little practice is necessary to judge properly the ex-?' he vapor pressure apparatus in its final form is shown hi Fig. I . The method of making the glass diaphragm is shown in Fig. 2 .