154 
PROFESSORS W. RAMSAY AND S. YOUNG 
The values of dpjdt were calculated in the same manner as with the other liquids. 
The pressures for one-tenth of a degree above and below the required temperature 
were calculated by means of the ecjuation log p — a -h and the difference 
was multiplied by 5 to obtain the vaHie for 1°. The pressures were reduced to 
grams per square centimetre, and the value of J was taken as 42,500. 
Temperature. 
■ 
dpjdt 
Si — 
L. 
° C. 
° Abs. 
mms. 
grms. 
C.C 3 . 
cals. 
80 
353 
15-99 
21-7 
957-00 
173-0 
90 
363 
22-73 
30-9 
642-00 
169-0 
100 
373 
.31-16 
42-4 
442-00 
164-0 
110 
383 
41-70 
56-7 
311-00 
159-0 
120 
393 
54-45 
74-0 
224-00 
153-0 
1.30 
403 
69-75 
94-8 
164-00 
147-0 
140 
413 
87-60 
119-1 
123-00 
142-4 
150 
423 
108-20 
147-1 
92-40 
135-3 
160 
433 
131-50 
178-8 
70-80 
129-0 
170 
443 
157-80 
214-5 
54-90 
12 -2-8 
180 
453 
187-00 
2.54-2 
42-90 
116-3 
190 
463 
219-00 
297-7 
33-80 
109-6 
200 
473 
254-00 
345-3 
26-60 
102-2 
210 
483 
292-50 
397-7 
20-90 
94-5 
220 
493 
334-00 
454-0 
16-20 
85-3 
230 
503 
379-00 
515-0 
12-30 
75-0 
240 
513 
428-00 
582-0 
9-03 
63-4 
250 
523 
481-00 
654-0 
6-29 
50-6 
260 
533 
540-00 
734-0 
3-64 
33-5 
The heat of vaporization of propyl alcohol at the boiling-point 97°‘4 would be 
165’2 calories. 
Pressui'es and Temperatures of Prop)yl Alcohol at Definite Volumes. 
In our previous papers we have given tables of the volumes of a gram of substance 
at definite temperatures and pressures. 
We have recently shown, however, in two papers read before the Physical Society 
of London and published in the ‘Philosophical Magazine’ (May and August, 1887), 
that, when the volume of a stable liquid or gas is kept constant, a very simple relation 
exists between the pressure and the absolute temperature, which is expressed by the 
equation 
j) = ht — a, 
where p> is the pressure, t the absolute temperature, and h and a are constants 
depending on the substance and on the volume occupied by a gram of it. 
We have, therefore, considered it better to construct lines of equal volume or 
“ isochors,” and to read temperatures and pressures from the isochors, rather than to 
read the volumes of a gram from isobars constructed from the isotherms. 
Owing to the directions assumed by the isochors, it is most convenient to give 
