354 BIOT ON THE EMPLOYMENT OF POLARIZED LIGHT ~ 
sively added which I have given in the place above cited of my 
memoir, I calculated the successive values of <, for the different 
systems formed; and by adding to it the observed density 6, of 
the primitive system, I determined by the equation (2.) the re- 
sulting density 6, which I compared with the densities actually 
measured, The elements of these comparisons are seen in the 
following table, constructed on the model of those which I have 
already given. 
Densi' 
Ponderable | Centigrade Density caicuistst Excess of 
proportion of | temperature | observed, | the formula 
Name of the ensity 
the primitive | at which the that of (2.), on the 
observed system. system €, | density } was |distilled water] hypothesis of py an 
observed. being 1. a simple a ee 
mixture. ensity 
Primitive tartro- FA 
sulphuric system 1:000000 13°5 1:25895 
Dy] ceeeeeccceeeeenees 
System =, deduced 
from 2%, by addi- +} 0°802047 13:0 1:24843 1:24715 | +0-00128 
tion Of 7 ecco 
System 3; deduced 
from > by aif 0-608232 13:0 1:23703 1:23580 | +0:00123 
tion Of 7 ....000e- 
The differences expressed in the last column of the table are 
so slight, that they could not be relied upon in experiments 
which had not been performed with a view to such an applica- 
tion ; and they may undoubtedly be neglected, especially on re- 
collecting that the value of §,, which is an element of the calcu- 
lation, has been determined from tables which were not perhaps 
exactly established for the same temperature. Thus, in this de- 
licate state of equilibrium, in which the characteristic function 
a(P+E) 
P13 
in the first system =, are diffused in the two others by simple 
dilution, without any reaction being exerted between them and 
the quantities of the mixture o subsequently added. 
45. But here are the proofs of the fact, which show that 
the converse of this proposition is not true, as I have stated 
above; that is to say, that in the present, as in many other 
cases of combinations, the chemical groups may experience 
very considerable modifications, which alter the characteristic 
function Ss not only in its absolute values, but in its sign, 
appeared nearly constant, the chemical groups formed 
