38 Oapt. A. 0. Egerton on the Vapour Pressure 



Detail of Experiments. — In Table I. are to be found the 

 results of the preliminary experiments with mercury. Tubes 

 A and B were made of glass with a platinum partition 











Table 



I. 









Platinum Plates 





Mercury. 







Tube. 



A 



A 



Time. Weight 



Area of 

 Hole. 



Length to 

 Deposit. 



Resist- 

 ance. 



Temp. 



° C. 



Vapour 

 Pressure. 



Remarks. 



2370 

 2360 



0-7867 

 0-7157 



0-0335 cm. 2 



6'5 cm. 



io-o „ 



80-46 



83-8 



33-7 

 33-8 



0-00399 

 0-00377 



Heated by 



Ether Vapour. 



B 



2160 0-6755 



0-0328 „ 



9-0 „ 



84-57 



34-3 



0-0039J 



,. 



B 



2730 08283 



>' >» 



8-7 „ 



84-21 



34-05 



0-00386 



V ) J 



A 



2317 0-1328 



0335 „ 



8-7 „ 



82-6 



15-5 



0-000646 



Thei'inostat. 



E 



(17H 



E 



(17 H 



697 

 oles) 



2844 

 oles) 



1-9105 



0-4193 



0-699 „ 



60 „ 

 7-0 „ 



8-98 

 9-5 



34-2 



o-o 



0-00366 

 0-000189 



Ice-Bath. 



E 



(17 H 

 E 



1878 

 oles) 

 2617 



2-7652 

 2-6247 



0-699 „ 



9-0 „ 

 8-5 „ 



11-68 

 11-0 



28-6 

 249 



00253 

 0-00179 



Thermostat. 



having a circular hole in the centre. Tube E had 17 

 circular holes. Before sealing on the platinum plates, the 

 holes were accurately measured. In the case of the plate 

 with many holes, a photographic enlargement was made, a 

 standard centimetre being enlarged at the same time. The 

 experiments show that, although the accuracy is decreased 

 in the latter case owing to the small resistance of the hole, 

 smaller vapour pressures can be determined by multiplying 

 the number of holes. Knudsen's correction for the tube's 



resistance, viz. 



3^2 

 8 • 



IP: 



7rJo - 



dl, appears to hold satisfactorily. 



Experiments were undertaken at various times to stan- 

 dardize the glass tube 0, the tube F with iron plate, and 

 the other tubes G and H, — these results are given in 

 Table II. The first experiments with tube C were made 

 in exactly the same way as the experiments with the platinum 

 plates, the mercury being heated in the upper portion of the 

 apparatus in a vapour- bath of ether. The other experiments 



