97 



As yet only a few readings have been made, and these were obtained 

 incidentallj^ while conducting tlie investigation referred to above. A curve 

 was platted (Fig. 2) in which temperatures are abscissas, and the cor- 

 responding currents are ordinates. Only the upper portion of the curve 

 is shown in the figure. The density increases very slowly at first, and 

 becomes constant when the critical temperature is passed. 



This method furnishes a means of determining the critical temperature 

 and critical pressure, as well as the critical volume of a liquid. 



An Improved Wehnelt Interrupter. 



[Abstract ] 

 By Arthur L. Foley and R. E. Nyswander. 



The chief difficulties encountered in working with the ordinary type 

 of Wehnelt Interrupter are that the glass tube which holds the platinum 

 wire is continually breaking and that the length and size of the project- 

 ing platinum wire can be changed only by constructing new tubes. 



In the improved interrupter a lead vessel serves as electrode and to 

 contain the electrolyte. The platinum wire is held in a brass tube 

 having its lower end slotted and conical. A collar, sliding on the conical 

 end, serves to press the jaws together and to clamp the platinum wire. 

 The projecting end of the wire may be about 1 cm. long; the remainder 

 of the wire may extend up the inside of the tube. 



The lead vessel should be filled half full of the electrolyte and over 

 this should be poured a layer of coal oil 2 or 3 cm. deep. The brass tube 

 is gradually lowered until the platinum point extends to the desired 

 depth in the electrolyte. The remainder of the platinum wire and the 

 brass tube are entirely protected by the oil. The oil serves also to 

 decrease the spray and fumes from the electrolyte. A platinum loop 

 instead of a point is preferable in many cases. The action of the inter- 

 rupter is made more constant. 



Many other electrolytes may be used besides the usual 10 per cent, 

 solution of sulphuric acid and water. As a matter of fact for high or low 

 voltages some other electrolytes are superior. The following tables gives 

 some data concerning a few of many electrolytes that liav3 been used 

 with this form of interrupter: 



