78.] 
VISCOSITY OF GASES. 
Table 82 — Viscosity of hydrogen — Continued. 
261 
p 
P 
t" 
To 
6" 
V 
l+4$»/M» 
F(6") 
125.07 
89.43 
. 89.41 
89.42 
77.43 
77. 4.", 
77.43 
77.43 
90 
480 
480 
480 
48.52 
48. 56 
48. 62 
48.98 
7 
7 
7 
7 
1428 
0. 0001579 
1574 
1564 
Bearing in mind therefore that the curve 
1+4 
F{6") = 
R" 
x + 4 i 
is given by these results, is necessarily high, I constructed F(&") both 
(or Table 81 and for Table 82. The result shows a most surprising 
legree of coincidence in the values for air and for hydrogen, proving 
|beyond a doubt that the same law of variation F{0") must apply to 
)oth gases. Since the , locus constructed falls below {l+a6")l, where 
y=().()036G5, the coefficient of expansion of gases, the true value of F(B") 
aiust fall decidedly below (l-\-ad")l and a fortiori below the formula 
'L =1 + 0.002751* 
0.00000034* 2 
>y which Holman reproduced the data of his fine observations for air 
>etween 0° C. and 100°. Now, although the data in the locus drawn fall 
>elow (1 + <*#")*, it can not at once be assumed that (1+ <*#")? is to be 
7)" 
liscarded as the value of -L- for in view of the occurrence of the factor 
//„ 
1+4 
R 
here C is essentially positive and increasing with 6", it does not follow 
hat F(6") and ' are identical. 
m 
The curve shows the effect of a cold environment in a very striking 
ray; for the Bunsen-burner temperatures here lie at only 850°, and 
,140° is the highest temperature reached by the blast-lamp. Clearly 
he mean temperature of the thermo-couple is only a nominal value for 
he mean temperature of the helix of platinum tube. This is proved 
>y the high values of F(0") for hydrogen at 1,000° ; for these large data 
re due to the fact that platinum is pervious to hydrogen, an effect 
rhich, in the following tables, does not produce a serious discrepancy 
ntil much higher temperatures are reached. 
(915) 
