328 C. Barus — Effect of Temperature and of Moisture 



Volumetric Comparisons. 



2. Apparatus. — The apparatus to investigate the relation of 

 the emanating activity of phosphorus to temperature is shown 

 in figure 1, the thermal part consisting of a coil of thin lead 

 pipe (-J- inch bore), Z, submerged in a large water bath of cop- 

 per, AB, 13 cm high, 15 cm broad, and 20 cm long. There were 

 21 turns of lead pipe, each turn 6 cm in diameter. The air com- 

 ing from the gasometer train by way of a desiccator at D y and 

 a stop cock, j^(fine screw valve), traversed this considerable 

 length of slender tubing, fully taking the temperature of the 

 water bath, thereafter to be discharged into the central straight 

 pipe of brass, ab* l*2 cm in diameter, containing the ionizers 

 (not shown). The charged air is finally conveyed into the 

 influx pipe of the color tube, C, by the removable short neck, 

 G. A thermometer, t, is placed in the water bath ; another 

 may be inserted into the end, b, through a perforated cork, so 

 as to be in contact with the ionizers. 



Care was taken that all changes of temperature should be 

 slow. Thus it took 3 hours for the temperature to rise from 

 5° to 13° in the following experiments, for instance. 



The ionizers, as usual, were strips of wire gauze, holding 

 thin pellets of phosphorus between them. They were inserted 

 into, or removed from the tube, ab through b. If saturation is 

 aimed at, an excess of freshly cut phosphorus surface should 



Table I. — Effect of the temperature of phosphorus on its emanation, 

 jet method : p = 4'5 cm ; influx air at 27°-28°. 



Steam 





10 2 x 





Color. 



dV/dt. 



6 





liter/ min 



°C 



Bl* 



85 



27° 



B1 + 



110 





Bl 



100 



30-8 





90 



30-7 



Bl 



95 



28-6 





100 



28-6 



Bl 



95 



25-2 





90 



25-2 



Bl 



80 



22-3 



B1 + 



90 



223 



Bl- 



61 



18-8 



Bl 



90 



188 



Bl 



75 



18-8 



B1 + 



115 



18-8 



B1 + 



60 



132 



Bl 



60 



13-2 



Bl 



70 



13-3 



opaque 



100 



13-3 



Color. 



10 2 

 dV/dt 



None 



None 



None 



Puffs faint 

 Puffs strong, ) 



greenish ) 

 Puffs bluish 



Do 

 Do. No perma- ) 



nent color f 



Greenish permanent 

 Faint yl. L 380 



green. 



Blue gray 280 

 Bl— 350 



All colors came out 

 intensely includ- 

 ing opaque 



5° 

 6 

 7 

 8-2 

 86 

 90 

 9 3 

 98 



10-2 



10-7 



10-9 



11-8 

 122 



12-8 



Color. 



10 2 x 



dV/dt 



B1 + 

 Bl 

 opaque 

 Bl 



70 

 65 



80 

 75 



Bl 

 opaque 



85 

 105 



Bl 

 B1 + 

 Bl 

 Bl 

 B1 + 

 Bl 

 B1 + 

 Bl 

 Bl 



90 

 110 



95 



90 

 105 

 100 

 100 

 110 



90 



12-8° 



12 8 



12-8 



13 



17-6 



17-6 



31-3 

 308 

 30 6 

 326 

 324 

 32 2 

 353 

 35-2 

 34 9 



*B1, blue: Bl + , dark blue ; Bl— , light blue ; y], yellow. 



