12 8. F. Peckham on the Distillation of Hydrocarbons. 
_ He then gives a number of rules, the result of his own expe- 
“1st. * * * the more the temperature of the actual boiling 
point of oil of definite gravity is above the temperature to which 
the same oil is raised, the greater is the quantity of light oil 
obtained. 
“Od The gravity of distillate resulting from reduction of — 
temperature will be directly proportionate to said reduction. -_ 
* © Jn distillation, the temperature, therefore, should always 
bo wie ners to the boiling point of the oil of the specific gravity 
ve (34, The difference between the temperatures of the two 
boiling ey viz: of the oil being subjected to distillation, 
and of t erived distillate, is in direct proportion to the 
height of the still employed, or to the facility for cooling the 
upper portions of the still. 
‘Ath, The intensity of the process of ‘cracking’ is propor- 
tionate to the suddenness with which the oil vapors are con- 
densed before leaving the still. 
“Sth. The difference in gravity between that of the oil dis- 
tilled, and the desired distillate, is in ~~ proportion to the 
quantity of water produced in the proce 
‘These laws are the same with Slesiasieies distilled under 
the ordinary atmospheric pressure, as swith those distilled in a 
vacuum, or under increased pressure.” 
It is very rarely that as many errors are included within as 
little space, and the entire discussion exhibits in a remarkable 
degree to what totally erroneous conclusions the results of close 
observation and experience may lead, when explained upon a 
false hypothesis. 
The operation of “cracking,” as conducted by Mr. Downer, 
consists in a slow distillation of oils of high specific gravit 
and high boiling point, in a still furnished with a high dome, 
the outer surface of which is freely exposed to radiation. As 
distillation those oils which are condensed at the | 
tem ‘at which the dome is maintained, instead of pass- 
ing into the worm and thence into the receiver, collect in drops 
Ps n the surface of the dome, and fall back upon the surface 
he oil beneath, which has meantime become heated above 
their boiling points. Mr, Young distills the oils under pressure, 
thereby Me cpa them at a temperature above their normal 
boiling points 
It is therefore bgbrines that the primary and essential condi- 
tion of “ cracking ” simply to subject the oils to a tempera- 
ture above their oiling points, or in other words, to super-heat 
their vapors. It will be found that for oils of the same density, 
