ON EVAPORATION AND DISSOCIATION. 
329 
Ileats of Vaporisation. 
From the well-known thermo-dynamic equation 
L dp t 
— Sg dt J 
the heats of vaporisation at definite intervals of temperature were calculated. The 
values of dp/dt were calculated by means of the formula : log p — a + bed -f- c/3 1 ; 
pressures were calculated for one-tenth of a degree above and below the required 
temperature, and the difference was multiplied by 5 to obtain the value for 1°. The 
pressures were reduced to gra mm es per square centimetre, and the value of J was 
taken as 42,500. 
Temperature. 
dpjdt 
s i — s 2 
L 
° C. 
° Abs. 
millims. 
grammes. 
C.CS. 
calories. 
0 
273 
1-861 
2-530 
17,802 
289-17 
10 
283 
3-160 
4-296 
10,043 
287-36 
20 
293 
5-150 
7-002 
5,898 
284-54 
30 
303 
8-067 
10-978 
3,607 
282-07 
40 
313 
12-202 
16-590 
2,275 
277-78 
50 
323 
17-890 
24-323 
1,483 
274-14 
60 
333 
25-473 
34-633 
993-5 
269-41 
70 
343 
35-381 
48-104 
681-4 
264-51 
80 
353 
47-91 
65-139 
478-4 
258-96 
90 
363 
63-54 
86-330 
342-6 
252-76 
100 
373 
82-57 
112-26 
249-6 
246-01 
110 
383 
105-81 
143=86 
184-6 
239-27 
120 
393 
133-10 
180-96 
138-6 
232-00 
130 
403 
165-41 
224-89 
105-1 
224-07 
140 
413 
202-52 
275-35 
80-75 
216-12 
150 
423 
243-95 
331-67 
62-46 
206-13 
160 
433 
294-70 
400-67 
48-58 
198-34 
170 
443 
349-95 
475-80 
37-97 
188-25 
180 
453 
411-15 
559-00 
29-73 
17716 
190 
463 
482-0 
655-33 
23-21 
165-64 
200 
473 
560-85 
762-54 
17-89 
151-84 
210 
483 
649-75 
88341 
13-43 
134-78 
220 
493 
747-9 
1016=8 
9-54 
112-53 
225 
498 
797-5 
1084=3 
7-83 
99-50 
230 
503 
851 ; 9 
1158-2 
6-16 
84-47 
232 
505 
875-0 
1189-7 
5-50 
77-73 
234 
507 
897-5 
1220-2 
4-82 
70-15 
236 
509 
921-0 
1252-2 
4=11 
61-66 
238 
511 
945-5 
1285=5 
3-25 
50-22 
238-5 
511-5 
951-7 
1294-0 
2-84 
44-23 
The heat of vaporisation of methyl-alcohol has been determined by Andrews, and 
by Favre and Silbermann, at the boiling-point under ordinary pressure. The 
former found 263'7 calories, and the latter 263'86 calories. At the boiling-point our 
results give 266'7 calories ; this is a satisfactory agreement. 
From the foregoing account of our experiments with methyl-alcohol it is evident 
MDCCCLXXXVII.—A. 2 U 
