EILLEBBAND.] FEKKOUS IRON. ( . » 1 
Filling, sealing, and heating of tht focbe. — The very finely powdered 
mineral having been introduced into a tube of resistant glass free from 
ferrous iron, the open end is drawn out, so as to leave a funnel for the 
introduction of the acid. A very little water is then introduced and 
carefully heated to boiling for a moment to expel all air from the 
powder. The diluted acid— which has just been boiled down from a 
state of greater dilution in order to have it free from air — is then 
poured in until the tube is about three-fourths filled. Carbon dioxide 
is then introduced from a generator which has been in active opera- 
tion for some time, through a narrow glass tube drawn out of the 
same kind of glass as that of which the decomposing tube consists. 
In a few moments the air is expelled, and the small tube is then scaled 
into the large one over the blast lamp without interrupting the gas cur- 
rent until the very last instant, when to prolong it would perhaps cause 
a blowing out of the softened glass. The interruption of the current 
at the proper moment is easily effected by the pressure of the thumb 
and linger holding the small tube at the point where it enters the 
rubber tube leading from the gas generator. No breakage in the oven 
ever occurs as a consequence of thus fusing one tube into the other. 
The heating is done in a bomb oven at any desired temperature up 
to, say, 200° C, and continued at intervals until examination by aid 
of a low-power lens shows that decomposition is complete or has pro- 
gressed as far as can be hoped for. By inclosing the glass in an outer 
tube of strong steel, properly capped * and containing a little ether or 
benzine to equalize the pressure on both sides of the glass, the tem- 
perature can be elevated far beyond what is otherwise permissible, 
and the decomposition will then doubtless be more complete with 
refractory silicates. 
Reason for introducing gas and sealing as above directed. — The 
usual practice in employing the above method has been to expel air 
before sealing by introducing a few crystals or lumps of an alkali car- 
bonate or bicarbonate, the gas set free on their contact with the acid 
being supposed to effectively expel all air. That this is not accom- 
plished the following series of comparative results long since pub- 
lished elsewhere 2 fully show. The material used was the oxide of 
uranium U 3 8 , requiring by theory 32.07 per cent of U0 2 . Operating 
as just above described on from 0.3 to 0.5 gram, the results were 
31.06, 31.07, 29.72, 29.33, 29.89, 30.69, 
whereas after filling the tube with gas from a generator there was 
found 
32.11, 31.90, 32.15, 32.12, 32.06, 32.17, 32.28, 
the average error of the former series being 1.78 per cent. The per- 
centage error would, of course, be reduced by increasing the weight 
iUllmann, Zeitschr. fur angew. Chemic, 1893, p. '274; Zcit. fur anal. Chemie, Vol. XXXIII, p. 582, 
1894. 
2 Bull. U. S. Geol. Survey, No. 78, p. 50; Chemical News, Vol. LXIV, p. 232, 1891. 
