BABU8.J 
CALIBRATION OF ELECTRICAL PYROMETERS. 
123 
heated at the same time to different degrees of redness. The mean tem- 
perature of the outside of crucible was measured and found to be 1,400°. 
Table 24. — Calibration in zinc vapor, November 10, 1887. 
Couple 
No. 
t. 
e. 
C20. 
Time. 
Furnace 
No. 
Mean «2o, 
37, 38, 39, 40. 
° G. 
Micro- 
volts. 
Micro- 
volts. 
h. m. 
Microvolts. 
37 
20.8 
11065 
11070 
1 40 
1 
11074 
37 
21.2 
11065 
11070 
1 50 
2 
37 
22.8 
11050 
11070 
2 5 
3 
38 
23.6 
10995 
11030 
2 14 
1 
38 
24.0 
11013 
11050 
2 20 
2 
38 
24.8 
11030 
11070 
2 30 
3 
39 
25.3 
11040 
11080 
2 40 
1 
39 
26.0 
11075 
11130 
2 45 
2 
39 
26.6 
11030 
11090 
2 50 
3 
40 
27.0 
10995 
11050 
2. 55 
3 
22 
27.3 
9883 
9950 
3 
3 
Table 25. — Calibration in tin. 
No. 
, 
e. 
e»o. 
Time. 
° a 
Micro- 
volts. 
Micro- 
volts. 
ft. m. 
22 
20 
15630 
15630 
6 30 
35 
21 
18460 
18468 
35 
22 
21 
15860 
15868 
40 
22 
22 
15300 
15317 
40 
22 
23 
16100 
16126 
40 
36 
24 
18950 
18984 
50 
37 
25 
18950' 
18993 
55 
An accident here stopped the experiment at intense white heat. It 
has been stated that a thick, viscous slag soon forms over the surface 
of the tin and the walls of the crucible, wholly enveloping the metal 
within it. A criterion for the boiling point of tin, therefore, will con- 
tinue to be difficult of determination. 
Table 26. — Calibration in bismuth. 
No. 
t. 
e. 
em. 
Time. 
° C. 
Micro- 
volts. 
Micro- 
volts. 
ft. m. 
22 
20 
11790 
11790 
6 
22 
20 
12620 
12620 
5 
22 
20 
13940 
13940 
15 
22 
20 
14800 
14800 
25 
22 
20 
15780 
15780 
30 
22 
20 
16380 
16380 
35 
22 
20 
16510 
16510 
40 
22 
20 
16630 
16630 
45 
22 
20 
15550 
15550 
50 
22 
20 
1C900 
16900 
55 
(777 
