Method of Determining Thermal Conductivity. 595 



(7) Calculation of Thermal Conductivity. 



The curves in section (6) b marked A — E fall within the 

 range suitable for calculating the thermal conductivity of 

 mercury. Remembering that the velocity is negative equa- 

 tion 5 of section (3) may be written for practical purposes : — 



where V is the weight of mercury escaping in the time t, 

 which w r as always 1 5 minutes, and 1? 2 are temperatures on 



the curve in question at distances -^ on the left and right 



respectively of the point on the curve at the same tem- 

 perature as the room. 



s the specific heat of mercury = "0333. 



A the cross-section of the tube was found = 5*98 sq. cms. 



t = 15 x 60 seconds. 



5LV 



The following are the values of — ^ — in each case, 



log™ 



Ox 



-02 



for each curve three different values of L being taken. 



V. 



5L. 



9 V 



■«r 



323 



f 2x26-; 

 i 2XS9-: 



L 2x51-: 



399 



283-190 190-13-4 

 352-190 19-0-11-4 

 43-4-19 190- 99 



2x35 36-5-19-5 

 \ 2x25 30-1-19-5 

 [ 2x48 47-7-19-5 



481 



25 j 



2x25 

 2X32 

 2x40 



311-19-2 

 36-5-19-2 

 439-19-2 



2x25 29-5-18-0 



497-97-1 i 2x35 36-9-180 



2x41 431-180 



54388 



2x24 29-8-18-0 

 2x30-5 34-9-18-0 

 2x35-5 40 5-18-0 



19-5-12-0 

 19-5-13-6 

 19-5-10-3 



19-2-13-4 

 19-2-12-3 

 19-2-11-3 



18-0-12-5 

 180-11-2 

 180-10-4 



180-12-5 

 180-11-6 

 180-110 



Abscissa 

 of room 



temp. 



5LV 



i i 

 3 



Mean. 



61-3 



77120 | 

 77240 I = 

 77380 J 



77250 



48 



78610 ] 

 78430 I = 

 78750 ) 



78600 



40 



77100 ] 

 77160 I = 



77770 J 



77340 



41 



77750 ] 

 78500 I = 

 78600 J 



78310 



35-5 



78750 ] 

 78670 [ = 

 76150 J 



77860 



■2Q2 



Mean = 77870 



