104 
Proceedings of the Royal Society of Edinburgh. [Sess. 
To enable neck-loss to be evaluated independently of the other modes 
of heat- transfer, an inner tube of cupronickel of the same length as the 
neck was slipped inside the latter, and the evaporation rates were again 
determined at the selected temperatures.* By inserting this extra tube, 
the sectional area was increased from 0*303 sq. cm. to 0*856 sq. cm. of 
metal. The enhanced rates of evaporation resulting therefrom are set 
forth in Table III. 
Table III. — Metal Flask : Evaporation Losses when Additional Tube 
WAS INSERTED IN NECK. 
Period of Test. 
Hours. 
Absolute 
Temperature of 
Outer Globe. 
0i. 
Absolute 
Temperature of 
Inner Globe. 
0 2 . 
Evaporation Loss, 
grams per hour. 
14 
283° 
82° 
62-5 
10 
317° 
82° 
89-4 
8± 
343° 
82° 
99*7 
j 7 
373° 
82° 
124T 
It will be observed that when the . outside temperature was 10° C. 
(283° abs.) the extra tube added 20 grams per hour to the rate of 
evaporation. By simple proportion, the neck-loss at this temperature when 
the additional tube was absent was 11 grams per hour. The equivalent 
losses at the other stated temperatures (Table IY) were obtained in the 
same manner. 
To make sure that the flask was not deteriorating under the treatment 
it was receiving, frequent check determinations were made of the normal 
evaporation rate at 10° C. There was no sign of deterioration. 
Table IY. — Metal Flask : Neck Losses Calculated from Foregoing Tables. 
Absolute 
Temperature, 
Outer 
Globe. 
^1- 
Increase of Evaporation 
due to insertion of 
Extra Tube, 0 - 553 sq. cm. 
section ; grams per hour. 
Evaporation per 
sq. cm. of Neck 
Section ; grams 
per hour. 
Actual 
Neck-Loss, 
grams per 
hour. 
283° 
20*0 
36-2 
11-0 
285° (25° C.) 
11-9 t 
317° 
28 T 
50-9 
15*4 
343° 
27-7 
50T 
15-2 
373° 
26*5 
48-0 
14-6 
t Interpolated. 
* This method of determining neck-loss is described in “ Grundlagen zum Bau von 
Transportgefassen fur verfliissigte Gase,” by F. Banneitz, G. Rhein, and B. Kurze, Annalen 
der Physik, vol. lxi (1920), p. 113. 
