838 C.M. Warren on a Process of Fractional Condensation. 
choking of the worm is a partial or entire stoppage of the stream 
of liquid which normally flows steadily from the end of the 
worm into the retort. Any interruption or unsteadiness of this 
flow would indicate too rapid ebullition. 
As a rule, other things being equal, the greater the difference 
between the temperature of the bath and that of the retort, the 
slower the products will come off, and the more effectual will be 
the separation. I think it possible, however, that the earlier 
fractionings may be conducted so slowly that the loss of time 
would more than counterbalance what might be gained by more 
thorough separation, and that equally good results may be more 
economically obtained by more frequent operations, somewhat 
more rapidly conducted. if 
A striking illustration of the advantage to be gained by this 
process is presented by the fact that, during the first fractioning 
of a crude mixture, such as American petroleum or coal-tar 
naphtha, for example, the difference between the temperature of 
the bath and that of the retort may sometimes be as much as 
5° C., ven more. While, as the products become purer, 
this difference between the temperatures of the bath and retort 
proportionally decreases, till finally, in operating on a pure pro- 
uct, the temperature of the bath must be brought to within a 
few degrees of that of the retort, in order to bring the vapors 
through. But the amount of this difference is variable for dif 
. 
ferent bodies of equal purity. 
retort, and by the relative quantities of the products obtained, 
—there might be something gained by exercising discretion 1” 
lowest fraction 
of the preceding series, which is large enough to operate upon 
by itself, is transferred to the retort, and brought into yess 
oe of the bath is then adjusted as above descr! ee 
and the distillation continued, the fractions obtained being pla 
‘90 4h abies: aig . f the retort 
in eo ecoprints bottles until the temperature 0 hich the 
