[mctaggart-edwards] METHAXE-NITROGEN 61 



Analyses 



The composition of any sample of methane-nitrogen was deter- 

 mined by estimating the methane by combustion and the nitrogen by 

 difference. The apparatus used was of the Burrell Gas analysis type. 

 A sketch is here attached, Fig. 1, showing the combustion chamber, 

 KOH absorption pipette and the measuring burette. This latter 

 could be read to hundredths of a cc. 



General Description of Apparatus 



Fig. 2 shows in diagram the essential features. The mixtures of 

 » methane and nitrogen were liquefied in a tube surrounded by a bath 

 of liquid oxygen. This part of the apparatus is shown in the centre of 

 the diagram and may be referred to as the cryostat. The mixtures were 

 admitted to it after passing through drying tubes of calcium chloride 

 and phosphorus pentoxide. Samples of the liquid and vapour phases 

 were drawn off over mercury in burettes shown on each side of the 

 diagram and collected in small sample tubes for analysis. In place 

 of glass taps it was found convenient at some points in the apparatus 

 to insert short lengths of rubber compression tubing which could be 

 closed by screw clips. These are shown at L, M, N, P, R, S. 



The Cryostat 



This is shown in detail in Fig. 3. The liquefying tube (a) was 

 closed by a rubber stopper through which four small tubes passed, 

 (b) used as exhaust tube as well as for the admission or withdrawal of 

 gas samples, (c) a capillary tube used to withdraw samples of the liquid 

 phase (this device was used by Baly, Phil. Mag. 49, 517, 1900), (d) a 

 tube for the thermocouple wires — one wire running down inside it, 

 the other outside — (e) a tube closed outside by a short length of rubber 

 tubing and containing a glass stirring rod, which could be moved by 

 hand through the rubber. 



The vacuum flask holding the bath of liquid oxygen had part of 

 the silvering removed so that the progress of liquefaction could be seen. 



The flask was closed by a rubber stopper and connected by the 

 tube (g) to an exhaust pump. By reducing the plessure to 5 cms. of 

 mercury a temperature of — 200°C. or lower could easily be reached. 

 The pressures in the liquefying tube and in the vacuum flask were 

 observed on simple mercury manometer columns. 



Manipulation 

 In carrying out an experiment with any mixture the following 

 order of proceeding was adopted. The liquefying tube was first 

 exhausted through (b), the vacuum flask being removed. The storage 



