( 1215 ) 
or 
mda fin dfn 
== (1 —m) —, 
adm m dm 
and so 
If we wish to determine the value of /; perfectly accurately, we 
are confronted, even with SypNry Youna’s determinations, by difficul- 
ties. SypNry Youre represents the form of p by the formula of Bior, 
viz. Log pat bel Heg; on the whole he succeeds in deter- 
mining the many constants occurring in the formula so that the 
agreement with the experimental data is very satisfactory. But though 
we confine ourselves to the socalled normal substances — so excluding 
acetic acid and the alcohols — yet appreciable differences occur, 
especially in the neighbourhood of 7). Differences great enough to 
mda 
be of importance for the value of (==) which is to be calculated. 
adm / her 
A very elaborate investigation would be required to determine the most 
probable value of f;. And perhaps the most reliable method for the 
calculation of this quantity is the direct one; viz. by reading as 
well dx as dm and a and m at temperatures near 7), from the 
table of the observations. As an example I calculate for ethyl-acetate 
from : 
p af 
ZOT eren 245 
ATA REE 247 
SEK ores ent 249 
BOBO a 250 
Boat: oR. ses 250,1 
\ uo Day mda 
From the two first observations follows for — or the value 
pd1 adm 
795 X 519 430  522,5 
vat tha Set and Att obgereution ee ey ee 
27137 x2 28585 
while the difference of the temperatures is too slight for the calcu- 
lation from the two last observations. The rise of p, which per 
degree is equal to 395 at 7=246, and to 430 at 7=249,5, would 
namely suddenly be equal to 770 at 250,05. Thus much we shall 
no doubt be able to conclude that /; will not differ much from 7,6 
or 7,8 for ethyl-acetate. I have thought I ought to call attention to 
this uncertainty of the absolutely accurate value of ft, as we shall 
