26 



EXPKRIM"E>T^ WITH IONIZED AIR. 



TABLE 3. -DUST REQUIRED AT DIFFERENT PRESSURES TO PRODUCE A GIVEN 

 COLOR (BLUE) AT A CiIVEN TEMPERATURE, 21°. 



Color. 



Lim 



Temp. 



Pressure. 



Remarks. 



"1 Field remains at about the same 

 I color while pressure, at constant 

 I dust contents and temperature, 

 J varies from nearly zero to 25 cm. 

 Field remains blue from 30 cm. as 

 far down in pressure as steam sup- 

 ply is available. Depth of color 

 changes with quantity of steam. 



8. Effect of Air lemperatnre. — Correspondiug to the preceding experiments 

 in which pressure is the only vai'iable, a correlative sei'ies of experiments was made 

 in which the temperature d of the inflowing air was alone permitted to change. 

 For this purpose air was taken from without and heated in the steam drum D, 

 figure 3, Chapter I. The results are summarized in the following tables, 4 and 5, and 

 are remarkable inasmuch as no certain effect of tem2)erature could be discerned 

 within the limits employed. 



These remarks, it will be seen on consulting the tables, refer to the colors 

 of the first order, chiefly- to the blues, and in this respect are in accord with the 

 two curves in the chart, figure 3, which mei'ge into each other in the blue region. 

 For the colors of the second order, howevei', as the curve shows, the effect of 

 temperature is not negligible. Moi'e dust is I'equired, cset. par., at low temper- 

 atures than at higher temperatures, a result wliich goes hand in hand with the 

 presumably greater supersaturation at the lower temperatures of the inflowing 

 air. 



TABLE 4.— DUST REQUIRED AT DIFFERENT TEMPERATURES TO PRODUCE A 

 GIVEN COLOR (BLUE), AT THE GIVEN PRESSURE, 5 CM. 



Color. 



i 



Lfm. 



Blue-Opaque , 

 Faint Purple. 

 Dull Blue". . . , 



Blue , 



Grecn-Vcllow 



Blue 



Yellow-Green 



Blue 



Faint Purple 



.00 



•75 

 .00 



.65 

 .70 

 .00 



•65 

 .00 



•65 

 .00 

 .90 



Temp. 



17° 



16' 



t( 



O 



•7 

 18' 



Pressure. 



5.5 cm. 



Color. 



Faint Indigo 



Blue 



Dark Blue.. 



White 



Blue 



Dark Blue . 



j While 



/ Blue 



I-lm. 



.00 

 .80 



1.00 

 .00 

 .90 



1. 10 

 .00 



'•'5 



Temp. 



24 



Pressure. 



5 cm. 



