18 :’, — 
increases continually as the strength of the solution increase* 
although the weight and volume of the deep both vary. 
Inversely the regularity of the variation of drop size in the 
ease of nitre, points to the absence of definite hydrates of that 
body. 
It would be easy but delusive lo construct a formula con- 
necting the specific gravity with the drop size or dee]) weight 
of the solution. But a graphic representation seems to show 
the connexion between the variables. 
In fig. II the abscissae of the curve C represent the quantities 
of nitre dissolved in the same quantity of water. The ordi- 
nates of curve C show the corresponding weights ; those of 
P, the corresponding volumes of the drops ; those of E, the 
corresponding weights of nitrate of potash contained in a drop. 
It is confessedly a matter of great interest and still greater 
difficulty to determine exactly the relation which exists he- 
V V 
tween a dissolved solid and its solvent. The question may 
perhaps receive additional light from experiments similar to 
the above but more extensive and with this special object in 
view. Comparing the tables VI and VII there can for instance 
be little doubt that the apparent irregularities in table VI are 
owing to the existence of definite hydrates of chloride of cal- 
cium, while the uniformity of the numbers of table VII show 
that no hydrate of nitrate of potash exists at this tempera- 
ture. If this be the true explanation we may certainly 
make use of the method of drop-weighing to trace the exist- 
ence oi 1 absence of hydrates in solution of salts, or generally 
the existence of definite compounds in mixtures. And thus 
perhaps Berthollcts hypothesis of reciprocal recomposition 
may receive confirmation or the reverse. 
An investigation of this kind would lead away from the 
present purpose. 
he have next to consider the influence which the variation 
in the chemical nature of the drop-forming liquid may exer- 
cise upon the drop-size in the case SLG. 
The liquids which were selected for this purpose were clio-* 
