1307 
line under its Own vapour pressure from s towards a. If now we 
again generate a little vapour which can be in equilibrium with the 
liquid a, therefore the vapour a,, the liquid « moves, with separation 
of /, along the saturation line under its own vapour pressure in 
the direction of 0. 
If, as assumed for the point 6 in fig. 8, the conjugation line 
liqnid-vapour (the line 6, 6) meets the saturation line under its own 
vapour pressure in the liquidum point 5, then, as we have seen 
previously, the system /’-++ L is converted, at an infinitesimal change 
in pressure, into “+ L’ + G’ without any solid substance either 
dissolving or crystallising. If, however, we withdraw a little more 
vapour, so that the liquid 5 is converted into d, Fis dissolved and 
d is converted into liquid e. Hence, on distillation the liquid s will 
traverse a part of the saturation curve of #’ under its own vapour 
pressure, first with separation of solid and afterwards with solution 
of the same. The point f in which all solid substance has again disap- 
peared will, as a rule, not coincide with the point « of the distillation 
curve rséuv. Starting from the point f, the liquid, on continued 
distillation, proceeds along a distillation curve fg. 
If no solid substance / did occur the liquid # would, on distil- 
lation, traverse the distillation curve rstuv; as now, however, 
solid matter /” appears, it first proceeds along curve rs, then along 
curve sb f and finally along curve fg. From the foregoing consider- 
ations it follows: if a distillation curve meets the saturation line 
under its own vapour pressure it proceeds starting from this point 
of intersection, along a part of the saturation line under its own 
vapour pressure and abandons it in another point along a distillation 
line which, with regard to the first one, has shifted. 
We may also express this as follows: If during the distillation of 
a liquid a solid substance /’ separates, the liquid leaves the distil- 
lation curve in order to proceed along a part of the saturation line 
of # under its own vapour pressure. As soon as, on continued 
distillation, the solid substance /’ again disappears, the liquid again 
proceeds along a distillation curve which, however, does not coincide 
with the prolongation of the first. The occurrence of the solid 
substance has, therefore transferred the liquid to another distillation 
curve. | 
Although, as stated above, the appearance of a solid substance 
generally causes the shifting of a distillation line, yet in some cases 
no shifting can take place so that the liquid after the disappearance 
of the solid matter traverses the prolongation of the original distil- 
lation curve, This will be the case when the vapour contains only 
