390 CC. M. Warren on Organic Elementary Analysis. 
the supply of oxygen only requiring attention. In the ordinary 
way, on the contrary, in which the heat is applied only on one 
side of the substance, the latter, if volatile, is constantly chang: 
‘ing position backward in the tube, necessitating a corresponding 
movement of the heat in the same direction, which requires 
constant care and considerable skill. 
This proceedure—referring to the immediate expulsion of 
liquid from the bulb, ete.—implies that that portion of the tube 
immediately forward of the bulb should not already be too 
warm, which might easily be the case with a body of very low 
boiling-point. It would then be necessary to expel the sub- 
stance from the bulb no faster than the oxygen would absorb it 
in the proper proportion; which, as experience has shown, may 
be easily accomplished. 
With a body of extreme volatility it may be necessary also 
to place a dish containing pieces of ice under the bulb; as even 
the temperature of the surrounding air might in such a case 
eause the substance to pass forward too rapidly. 
8. The oxgen is admitted through Liebig’s potash bulbs con- 
taining sulphuric acid; and the carbonic acid formed is absorbe 
by similar alba with potash; to which is attached a tube filled 
not extend much backward of that part of the tube where it is desired that the 
combustion should take place, so that the temperature of the principal part of the 
column of asbestus may remain under the control of the operator, by means of the 
ca , or otherwise. 
~ Indepe of the use of a metallic bar, as described above, or any novel 
a : 
i the heat can be lated by this furnace with a nicety as great as, Or eV 
by the use of Th itions in this furnace, between the cocks, 
are two apart; so that the gas from one of the jets ignites bout two inches 
of the tube. To rely, therefore, alone u the cocks for regulating t 
burning the substance, would doubtless often lead to bad Its; but the heat ~ 
be made to approach the substance in the m adual ner,—next to 
: by a metallic bar,—by making use of a piece of thin Loge about 
_ two inches and half an inch wider than the top of the furnace, t 
If this ple 2 is laid on the wire gauze covering the furnace, conn 
th ee ee nee 
e from igniting under it, the gas 
all | soe om. igniting d of the plate, and to 
