120 
MEASUREMENT OF HIGH TEMPERATURES. 
[BULL. 54. 
ebullition as to vary the boiling point very perceptibly. Results oi 
of this kind are succinctly given in the following table. Succinic and 
pyrogallic acid, for instance, are failures, whereas naphthaline, benzoic 
acid, and camphor, when heat is applied gently and gradually, supply 
almost as fixed a boiling point as inorganic substances. In the case oi 
solids like the present there are two distinct planes of demarkation ob- 
servable. The first of these is the plane of ebullition, and coincides 
with the mean surface of the agitated liquid. The other is the plane of 
condensation or of solidification, and is marked by an opaque ring of the 
substance encircling the inside of the tube. The distance between these 
planes can be enlarged at pleasure by cautiously increasing the inten- 
sity of the flame of the ring burner, or by surrounding the boiling tube 
with a thick jacket of asbestos wicking. Of course it is advisable to 
insert the hot junction in vapor just above the plane of ebullition. 
Most of the results of Table 22 are obtained by older and more primitive 
forms of apparatus, and could be much improved by conducting the ex- 
periments in the new forms. The table also contains corrosive sublimate, 
which has a very convenient boiling point for many purposes. 
Table 22. — Available substances for boiling-point experiments. 
Elem. 
No. 
Substance. 
020. 
T. 
Time. 
Remarks. 
Micro- 
volts. 
° a 
36 
Corrosive subli- 
2632 
300 
■ 
'Apparatus closed by corks, both of which 
mate, HgClj. 
2627 
2606 
2639 
300 
299 
301 
are charred. 
2649 
303 
> Not taken. 
s . 
2631 
300 
12 cm above surface of liquid (melted HgCh). 
In vapor. 
2631 
300 
6 cm above surface of liquid. In vapor. 
2647 
303 
. 
( cm above surface of liquid. 
36 
Succinic acid ... 
2094 
255 
1 
f The acid boils brown, i. e., chars and gums 
2083 
255 
( 
.-. boiling point rises rapidly. 
2104 
256 
} Not taken. 
\ 
2240 
270 
| 
Ebullition intensified. 
2300 
276 
J 
( Liquid very dark brown. 
36 
Naphthaline 
1741 
210 
h. m. 
1 45 
Boils well and clear; combustion tube ele- 
1696 
205 
55 
ment 2 nm above surface of liquid. Very 
1696 
205 
2 
distinct planes of demarkation. 
1691 
205 
8 
1679 
204 
15 
1692 
205 
20 
1730 
209 
55 
More naphthaline added. This obviously 
1730 
2C9 
57 
changes the composition of tbe mass and 
the boiling point. 
36 
Pyrogallic acid.. 
1818 
218 
No constancy of temperature. Decomposed, 
forming a viscous mass. 
(774) 
