814 
with other com 3 being sufficient to vitiate 
the conclusions deducible from our experi- 
ments. Having ascertained the purity of our 
substance, the next care is to ensure its com- 
lete desiccation. For this purpose the fol- 
owing plan, recommended by Liebig, will be 
found the most efficient (fig. 429). A small 
quantity of the material to be dried is placed 
in an inverted syphon-tube (c), the bend of 
which is plunged into a vessel (D), contain- 
ing water gradually heated to the boiling 
point. When plain water is used, the tem- 
re of course will not rise above 212°; 
ut by substituting for it different saline solu- 
tions we may at pleasure obtain any degree of 
heat between 212° and 300°, according to the 
nature of the compound to be analysed. A 
current of dry air is made to pass over the 
substance by connecting one limb of the sy- 
hon with a tube containing chloride of calcium 
EA), and the other with a vessel (E) closed at 
top, excepting the aperture by which it is con- 
nected with the syphon-tube, and filled with 
sa which is allowed ae run out at the 
ttom with a s regulated by a stop-cock 
(f), the place oP the liquid being supplied by 
air, which has passed over the chloride of cal- 
cium and then through the sypbon-tube. Vo- 
latile liquids that are unchanged by distillation 
shoal te allowed to stand two or three days 
upon fragments of fused chloride of calcium; 
the liquid should then be decanted and dis- 
tilled in a small retort; in other cases, as in 
the examination of fats or fixed oils, it may be 
more convenient to dry the material in a watch- 
glass placed in an ordinary water-bath or the hot- 
water oven previously described. The further 
progress of the analysis will vary according to 
the form and composition of the substance to 
be examined. 
We shall describe the methods of analysing— 
1. A solid, which does not contain nitrogen. 
2. A fluid, which does not contain nitrogen. 
3. A substance, which does contain nitrogen. 
1. Analysis of a solid not containing nitrogen. 
The combustible which answers best in these 
experiments is charcoal ; it is the least expen- 
sive, and very manageable, but dusty. Spirits 
of wine or pyroxylic spirit, no doubt, are 
cleaner, but their expense is a great objec- 
tion. Gas has been tried by myself and others 
ORGANIC ANALYSIS. 
in a variety of ways, but though some modi- 
fications of burner answer tolerably well, it is- 
not on the whole to be recommended. és 
The best furnace to be used with the char- 
coal is represented at A, fig. 430, and is made 
of stout sheet-iron bent into the form of a 
trough, open at one end; the plate which 
closes the other is perforated with an aperture 
three-quarters of an inch in diameter, to allow 
the passage of the combustion tube; the fur- 
nace is about twenty inches long, five inch 
at top, two inches and three-quarters at bottom 
and three inches high. Transverse slits are 
made along the floor at intervals of two inches 
for draught, and between each are rivetted ve 
tical stiff pieces of sheet-iron one inch high 
terminating in a concave edge above, for the 
support of the combustion tube. The appi 
ratus may rest on bricks during the operatio 
as represented in the wood-cut. ra 
The tube in which the mixture is burne 
the combustion or retort tube, (fig.430, a, b, ¢,) 
should be of difficultly fusible glass free fre 
lead, about fifteen insta long and half an ine 
in diameter: the hard Bohemian glass an: 
the purpose perfectly. The tube may on cer 
tain occasions be drawn out into a fine 
strong tail bent upwards at an obtuse an 
and the mouth should be smoothed by makir 
it red hot in the flame of the blowpipe, | 
that a cork need not be torn in adjusting it. 
The apparatus for containing the chloride ¢ 
calcium which collects the water, or dryin 
tube, is conveniently made of the shape 
picted (fig. 430, B): it consists of a t 
about half an inch in diameter and four ine 
long. Upon one end is blown a bulb, to cc 
a larger portion of the chloride, and fre 
bulb a strong tube of small diameter exten 
for an inch anda half. The chloride of ¢ 
cium with which it is filled must not be fuss 
but should be prepared merely by evapor. 
the solution of the chloride in 
strong sand heat. A porous mass is thus 
tained, which does not crystallize by absorb 
moisture, as the fused variety does, to the 
struction of the tube that contains it. In 
to charge the apparatus a few fibres of co 
wool are put into the bulb, and by sucki 
through the small end adjusted over the a 
ture of the fine tube to prevent any m 
particles from falling out: into the app 
ie Fated 
© Fig. 430. 
* > d. I 
: b as eee 4 
Vari re ot O~ 
VV ~ tas 
— Pe ee ee 
: Sor the combustion of organic bodies. 
A, sheet iron trough or furnace containing the retort tube a, b, c, and resting on 
Liebig’s 
the bricks E E. 
B, the drying tube charged with chloride of calcium, or pumice stone moistened — S by 
with sulphuric acid. 
e, the potash bulbs; d, caoutchouc connector. ak a 
D, the suction tube, shewing the mode of its adjustment when used for draw- 
ing air through the apparatus at the termination of the experiment. ray 
eae 
~ 
