or THE DESTEHCTIVE DISTILLATION OE BOGHEAD COAL. 
451 
is, of course, passed over the reduced metal to remove any carbon which may have com- 
bined with it. The tube is arranged as in the annexed sketch. 
At a is placed a small plug of recently ignited asbestos, about two centimetres long ; 
then a mixture of fused and powdered chlorate of potash and oxide of copper as far as 
h (about seven centimetres) ; then at c two centimetres of asbestos, followed to k by the 
same length of coarse-grained oxide of copper. The substance is placed at the tube 
to f being filled completely by granular oxide of copper of about the coarseness of ordi- 
nary gunpowder, and, finally, at g is placed another plug of asbestos. The combustion 
is commenced by heating the end a to redness, and between the screens h and ^ ; when 
fully red, the space between the screens k and I is filled with live coals, the whole of the 
fluid being immediately driven amongst the oxide of copper occupying the space from 
d to i. In a short time this oxide becomes sufficiently hot to cause a perfectly steady 
distillation of the fluid over the red-hot column of oxide from ^ to A, where it is burnt. 
No farther attention is requisite until carbonic acid ceases to enter the bulbs, when the 
screen ^ is removed back ; but it is always found, if the fluid is moderately volatile, that 
very little remains. When the tube is red-hot from h to /, the mixture of oxide and 
chlorate is slowly heated to redness. Combustions made in this manner seldom fail to 
yield good results. One great advantage of the method is, that if the space from Hod 
be of the proper length, there is no fear of either a sudden rush of gas or of the operation 
being tediously slow. All the fluid analyses given in this paper were made in this 
manner. 
On the Hydrocarbons unacted on by Sulphuric and Nitric Adds. 
The lowest fraction obtained during the rectifications was between 65° and 71° ; the 
quantity was far from large ; and although working on a tolerably extensive scale, great 
care was requisite to prevent loss by evaporation during the distillation. The density at 
15°‘5 of the crude hydrocarbons was only 0'735, although containing a considerable per- 
centage of benzole. On treatment with highly concentrated fuming nitric acid, in the 
manner previously described, and placing the acid and nitrocompound in a conical glass, 
for the purpose of facihtating the separation of the hydrocarbon unacted on by acids, I 
was surprised to find that no separation whatever took place ; and on throwing the 
mixture into water, no nitrocompound fell to the bottom, the whole rising to the surface 
in the form of a pale green layer. The latter was therefore separated, placed in a 
retort, and the heat of a water-bath applied ; a considerable quantity of a colourless 
fluid distilled over, which was treated several times with fuming nitric acid to remove 
any of the other hydrocarbons present, the last traces being retained with such tenacity 
that the process had to be repeated many times before the separated acid no longer 
3n2 
