14. S. F. Peckham on the Distillation of Hydrocarbons. 
temperature to force the vapors from the still, Such has been 
my experience repeatedly on both the large and small scale, 
Slow distillation yields the hydrocarbons unchanged, provided 
the vapors have ready egress from the still, because distillation 
is then carried on at the lowest temperature attainable. Small 
retorts are used for the manufacture of gas, in order that the 
coal may the sooner be raised to the red-heat, and the greatest 
possible “cracking” effect be experienced, while revolving re- 
torts are used in the manufacture of oil, not that the charge 
may be repeatedly cooled, but in order that it may be uni- 
formly heated, avoiding the necessity of over-heating the por- 
tion next the fire, in. order that the upper portion may be 
which the top of the still is maintained, the lower will be th 
boiling point of the liquid resulting from the condensation of 
the vapors that escape. : 
His fourth rule is too obscure in its signification to admit of 
His third rule is correct, as the lower the temperature at 
i e 
iticism. 
His fifth rule is of the most extraordinary character. Chem- 
istry is not yet ready for the announcement of the transmuta- 
tion of one element into another, and such transmutation must 
inly take place if warER can be produced by distillation 
of volatile HYDROCARBONS, with exclusion of oxyeEN. So, too, 
is it almost equally difficult to imagine how any general laws 
can be “the same” for two processes so diametrically opposed 
as distillation in a vacuum and under pressure. 
I desire in this connection to note a few suggestions which 
have occurred to me in reference to this subject. In the last 
edition of Prof. Dana’s Mineralogy (1868), he has classified the 
results obtained by Profs. Warren and Storer, and arra 
the hydrocarbons isolated by them in three groups, viz: the 
Naphtha and Beta-naphtha series, and the Pittoleum group. 
The first two are isomeric, the last contains more carbon in 
proportion to its hydrogen. The members of the Pittoleum 
group at present isolated are doubtless the lower members of a 
