BAD 
“O- 
NATURE 
[APRIL 29, 1915 


had been first noticed in America in 1861, and was 
patented in England by James Young in 1865. 
Thorpe and Young took 34 kilos. of paraffin 
wax obtained from shale and distilled it in an 
iron mercury bottle connected with a second by a 
bent tube carrying pressure gauge and stop-cock. 
The distillation was carried out over an open coal 
fire, one bottle containing the parafin being 
heated, whilst the other acted as a condenser. In 
about four or five hours the distillation was com- 
pleted, the pressure throughout being kept at 
25 lb., and a magma of oil and unaltered paraffin 
resulted, which could be liquefied completely by 
the warmth of the hand. Four litres of liquid 
hydrocarbons were obtained, and on a preliminary 
factionation gave :— 
Below 100° C. os Sot o°3 litre 
100-200" C. ee 50 Be 10 
200-300° C. 
au, litres 
Repeated distillations of the portion boiling below 
100° C. resolved it almost entirely into three frac- 
tions :— 
(1) 32°-38° C., consisting of pentane and amylene 
(2)h65.=70n G., ah Ran hexane and hexylene 
(3) 94°-97° C., iene heptane and heptylene 
Members of the acetylene and benzene series were 
absent. 
Extended experiments with the portions distil- 
ling from 100°C. up to 300°C., and the solid 
hydrocarbon left above 300°C., showed them to 
be mixtures of saturated hydrocarbons and ole- 
fines. In the fractions distilling below 100° C., 
these two classes of bodies were in nearly equal 
proportions, but above that temperature the pro- 
portion of paraffin hydrocarbon to olefine became 
gradually larger as the molecular weight in- 
creased. 
In cracking a heavy oil there are two factors 
that govern the course of the actions taking place, 
and these are temperature and pressure. The first 
loosens the groups of atoms that build up the 
complex molecule; the second to a great extent 
determines whether the action is a dissociation or 
a decomposition. 
The temperature at which the dissociation takes 
place is above the boiling point of the heavy 
hydrocarbons, and if no pressure is employed the 
oil vaporises and the amount of alteration that 
takes place is small and depends on the local 
heating of the vapours as they are formed, but if 
pressure is used the necessary temperature for 
dissociation is reached, and by suiting the tem- 
perature and pressure to the particular mixture 
of heavy hydrocarbons being dealt with, the 
maximum of alteration with the minimum of de- 
composition can be attained. Directly the action 
commences to be decomposition, gases are 
evolved, and carbon with heavy asphaltic bodies 
make their appearance in the residual liquid, while 
the volume of gas affords an index to the amount 
of decomposition taking place. 
The more complex the original molecule the 
lower the temperature needed to loosen the bond- 
age of the groups it contains, and therefore the 
NO. 2374, VOL. 95] 


easier to prevent decomposition; hence Thorpe 
and Young, using a nearly uniform compound like 
parafhn, were able to dissociate it entirely at a 
temperature of between 300°C. and 400° C., and 
prevent decomposition by distilling and condens- 
ing under a pressure of 25 lb., but when we come 
to deal with a mixture of complex molecules, such 
as are found in Solar oil, the dissociation tem- 
perature of some is well above the decomposition 
temperature of other molecules, and the tempera- 
ture at which it is best to carry on the conversion 
can be found by determining the temperature at 
which part of the oil just commences to decom- 
pose, 1.e., gives off 10 or 12 cubic ft. of gas per 
gallon at atmospheric pressure, and then to regu- 
late the pressure so as to prevent any gas being 
evolved. 
With a Solar or other residual oil, what is 
wanted is a temperature round about 500° C., and 
a pressure that may run up to 1ooo Ib. or more 
if heavy oils are being treated. It is also clear 
that the heated hydrocarbons must be cooled 
down under pressure to prevent the chance of a 
and to prevent the escape of the more volatile 
products of the conversion as vapours. 
It was this principle that was embodied in the 
apparatus which was patented by Sir Boverton 
Redwood and Sir James Dewar in 1889, and has 
been copied in the Burton process by which, at the 
present time, thousands of tons of heavy residual 
oils are being converted into lighter products by 
the Standard Oil Company. In both cases the 
form of apparatus is identical; large vessels or 
boilers are employed, and the pressure is re- 
stricted to 4 or 5 atmospheres, whilst the tem- 
perature is 400°C. to 500°C. 
Burton’s patent was granted on the grounds 
that by his process only hydrocarbons of the 
paraffin series were formed, whilst in all previous 
processes a mixture of the saturated and un- 
saturated series was produced, this idea being 
due to the fact that the bulk of the unsaturated 
hydrocarbons formed were naphthenes. 
The inventor of another process obtains greater 
safety by heating the flowing oil in a coil of iron 
tube heated to about the same temperature 
(450° C.) in a bath of molten lead at a pressure 
of 4o to 50 atmospheres, the oil then flowing to 
a second coil in a water condenser; this process 
differs from the previous ones by the pressure 
being kept sufficiently high to prevent any vapor- 
isation. These processes may be taken to repre- 
sent simple conversion, and the products found 
in the low boiling portions are chiefly paraffins, 
olefines, and naphthenes. 
A very interesting process for making 
“cracked” spirit is that devised by Mr. W. A. 
Hall, in which dissociation, decomposition, and 
recombination all play a part, as after vaporising 
the oil and passing the oil vapour at a rapid rate 
of flow through a great length of tube heated 
to about 600°C. under a pressure of 60 Ib., he 
suddenly lowers the pressure by allowing the 
| heated and decomposing oil vapours to pass into 

decomposition temperature existing in the liquid 
