34 



KXPEEIMENl'S WVIU. lOXIZED AlK. 



2. Method and A])paiutus. — The method of experimentation has been indicated 

 in the juvcedini; chapter, and is based on color criteiia obtainable with the steam 

 jet. Here I need only recall that a current of moderately dry air is furnislied by a 

 gasometer train (Mariotte flask, volume flask, pressure gauge, dessicator) terminat- 

 ing in the fine screw stop-cock I*] figure 1. On opening the latter, this passes 

 throufjli the phosphorus tube P (containing pellets of phospliorus l)etween strips 

 of wire irauze), where it is highly charged with the ionized emanation. This satur- 

 ated air is conveyed into the color tube CO' (old pattei-u of which ;' is the simple 

 jet), through the absorption tube f, of the length, diameter, and material to be 

 examined. The tube t is sealed into 7', while the other end dips slightly into the 

 lateral influ.v j)ipe C', of the color tube. The arrangement of C (length, etc.), has 

 very little, if any, effect on the results, as was i)ointed out in my last pajier. The 

 draft due to J is sufficient to capture all the nuclei from the open end of the 

 absorption tube t, and the whole of it is impressed on the jet. 



8. Jienidts for thin tnhe><. — To illustrate the method of work the chief <lata for 

 each tube are given in the following table. Other results are briefly summaiized 

 or expressed in the chart. Length, x, and radius, r, refers to the absorption tubing 

 employed. The volume ( F liters per minute) of charged air passing through P is 

 the amount needed to produce a definite color (full blue) in the field of the color 

 tube C. The velocity of the air current through t is given under v incentims. per 

 second. The constant h, in the final column, is the absorption velocity, computed 

 from the equation ^=2.65 ( V/rx) In ( V/ V^, where Fq is the volume in liters per 

 minute criving the identical blue color when the absorption tube t, is removed, and 

 the phosphorus tube conveys its contents directly into C. The other data (/>, the 

 pressure of the steam issuing from the jet, always low, and 6, the temperature of 

 the air at influx, measured by the thermometer T), are of little immediate interest. 

 Their variations are not important. 



In most cases, many observations (often four or five) were made for each tube 

 leno-th, X, in each series given, the difficulty being to select the same standard l)lue. 

 Tiie table contains only the mean values. 



T.\BLE I. 



ABSORPTION OF PHOSPHORUS DUST IN TUBES. 

 DL\MKTER, 2 ;• = .64 cm. / = 4 cm. = 26°. 



GR.JkY RUBBER. 



