( 374 ) 
From here we proceed with continued heating and constant loss 
of water along the line FG to solutions gradually getting poorer in 
water until we should have reached in G the boiling point of the 
salt itself. 
I will now call the point # the second boiling point of the 
saturated solution. This solution, however, will not show the phe- 
nomenon of boiling on heating but on cooling. We may for that 
object proceed along the reverse way, melt the salt, bring it in 
contact with water vapour which would yield the solution corres- 
ponding with C and cool the same. If we continue passing H20 
over or through the liquid this will absorb more of it as ¢ decreases 
until the point / is reached. On further cooling, solid salt would 
erystallise and the pressure consequently increase along /’B; this 
not being possible at 1 atm. pressure the liquid in / boils to dryness 
on cooling — the temperature remaining again constant. 
It is a very remarkable sight to see the boiling start as soon as 
the hot liquid commences to deposit solid salt and the phenomenon 
may be accelerated by taking the vessel out of the oilbath in which 
the melting of the salt and its saturation with aqueous vapour took 
place. The quicker the vessel cools the more rapid the boiling takes 
place. On continuing to cool, absorption of aqueous vapour ought 
of course, to take place again at Z. 
The following table contains the observations collected by Dr. Smits. 
Salt. List Eoiling point. 2nd Boiling point. Melting point. 
| 
K NO, 115 331 334 
Na NO, 120 310 313 
Na ClO, 126 255 261 
Ag NO, 135 Won 208 
TINO, 105 196 205 
From this list it appears that the second boiling points are 
generally situated close to the melting points. This follows from 
the small value of the temperature interval which will generally exist in 
systems containing salts and water between the points B and C on 
account of the great heat of evaporation of the water, causing the 
point B, and even more so #, to correspond to solutions containing 
very little water. 
