62 



Proceedings of the Royal Irish Academy. 



D 



Measurements of the Coiulensatiorb-Nuclei. 



The number of nuclei per c.c. of the gas at any tune was obtained by 

 means of Aitken's counting apparatus described in detaU in the "Proceedings 

 of the Eoyal Society of Edinburgh," vol. 18, g jr 



pp. 39-52. As this form of the apparatus, 

 however, is suitable only for measurements in 

 air in which there are comparatively few nuclei _ 

 — less than 10,000 per c.c. — and as the num- 

 bers per c.c. in the flame-gas were as high as 

 1,000,000, it was necessary to dilute the ^as 

 containing the nuclei with a known volume of 

 filtered air so as to get a concentration suitable 

 for measurement with the counter. The dilu- 

 tion was made in the apparatus shown in fig. 5. 

 -4 is a glass vessel of about 250 c.c. capacity 

 fitted with taps at B and C. i) is a three-way 

 tap by means of which the vessel A may be 

 put in communication with' the T-piece F or 

 the tube E, which itself is fitted with a three- 

 way tap G, leading either to the Aitken appa- 

 ratus or to a gasometer filled with thoroughly 

 filtered air. Below the tap B there is a flexible 

 tube attached, by means of which the vessel A 

 is connected to a cistern containing mercury. 

 By raising this cistern the whole vessel may be 

 filled with mercury up to F. At K there is 

 a short length of rubber tubing. The gas to 

 be tested flows from the gasometer through 

 the tube EF. In making an experiment the 

 tap D is turned to give communication be- 

 tween A and F, and the whole vessel is filled 

 with mercury up to F. The mercury cistern 

 is then lowered untU there is a known volume, 

 say 10 c.c, of the gas below D in the tube 

 DC, which is graduated. The tap D is then 

 turned round to connect A and F, and the tap G is turned so as to 

 connect with the gasometer containing the filtered air. The filtered air 

 is allowed into A until a certain volume, say 200 c.c, occupies the vessel 

 below C. The taps B and C are then closed, and, by making the remaining 



K 



Fig. 5. 



