Laboratory. 
ont of a tube of glass, and tbe common 
blow-pipes sold at the ironmongers for a few 
pence, and in universal use with workmen 
are very good. Others more costly and 
elegant, which have a small space for the 
condensation of the vapour of the breath, 
are sold by the makers of chemical appara- 
tus. It requires some address to produce 
a constant stream of air by blowing through 
this pipe ; but the principal artifice con- 
sists in keeping the tongue to the roof of the 
mouth, and using the breath by the pressure 
of the muscles of the face instead of the 
chest. Some workmen in glass contrive to 
hold the pipe steady between the teeth, 
and by that means have both hands at li- 
berty for use ; but as this requires uncom- 
mon steadiness in the head, the philosophi- 
cal chemist will probably prefer fixing his 
pipe to one of his stands. Some blow-pipes 
have been made, through which a stream of 
vapour from boiling alcohol is urged ; but 
these instruments seem to be rather toys 
than of use to the actual chemical investi- 
gator. It appears preferable to use bel- 
lows, as the enamellers do, where an ex- 
tensive application of this implement is re- 
quired ; though in this case the desirable 
requisite of portability is lost sight of. 
The bodies intended to be heated by the 
blow-pipe must not, in general, exceed the 
size of a pepper-corn, unless bellows and a 
very large flame be used. The proper sup- 
ports are either a piece of smooth, close- 
grained charcoal, for such bodies as are not 
subject to an alteration of their properties, 
from the inflammability of the coal, as 
might be contrary to the nature of the in- 
vestigation. This support is therefore most 
frequently used ; as it is properly adapted 
for saline, earthy, and many metallic bo- 
dies. The other support consists of a spoon, 
somewhat less than a quarter of an inch in 
diameter, maile pf a metal not subject to 
oxydation ; that is to say, pure gold, silver, 
or platina, or such a mixture of these me- 
tals as might be found to be least deficient 
in the requisite degree of hardness, which 
gold or silver alone does not possess. Berg- 
man advised to add one- tenth of platina to 
a given mass of silver. There is, however, 
no very considerable inconvenience result- 
ing from the use of a small spoon, either of 
gold or of silver; and platina possesses 
every quality which can be wished for. 
The small metallic spoon must of coui’Se be 
properly fixed in a socket of metal, pro- 
vided with a wooden handle. 
Very small or pulverulent substances are 
apt to be carried away by the current of 
flame. These may be secured by making a 
small hole in the charcoal, into which the 
powder is to be put, and covered with ano- 
ther small piece of charcoal, which partly 
protects them from the flame. Some experi- 
ments of reduction are made by binding 
two small pieces of charcoal. together, cut- 
ting a channel along the piece intended to 
be the undermost, and making a cavity in 
the middle of this channel to contain the 
subject matter of examination. With this 
apparatus the flame is urged through the 
channel between the two pieces of coal, 
and violently heats the substance in tile ca- 
vity, which may be considered as a closed 
vessel. 
A great nninber of mineral bodies are 
not fusible by mere flame, urged by com- 
mon air through the blow-pipe ; though oxy- 
gen gas subdues most bodies. See Gas 
oxygen. 
Whenever, therefore, the fusion of any 
refractory substance is to be attempted, 
some other substance must be added which 
is mare fusible, and capable of dissolving 
the former. These solvents, in the dry way, 
are distinguished by the name of fluxes, 
and, like the solvents used in the humid 
way, are mostly saline. It may easily be 
imagined, that the nature of the products 
will greatly vary, according to that of the 
flux, which enters into combination with 
them ; and accordingly tliey are varied in 
experiments, as well as in operations, in the 
large way. The blow-pipe experiments, 
though conducted upon the same principles 
as those upon a larger scale, differ never- 
theless from them in two particulars ; name- 
ly, that the whole of the phenomena are vi- 
sible throughout, and that the residues are 
of no value, otherwise than as they serve to 
indicate facts. For these reasons, every 
flux, without exception, might be used with 
the blow-pipe, provided it were not of such 
a nature as to sink into the charcoal. We 
may therefore select a certain small num- 
ber of the most convenient fluxes, and note 
the effects vvhich they respectively produce 
upon the various mineral bodies; and these 
will serve as indications to enable the che- 
mical enquirer to distinguish them again 
with a great degree of accuracy, not to 
mention, that he may also derive much ad- 
vantage, with regard to the more extensive 
operations he might be disposed to under- 
take. A considerable part of this prelimi- 
nary labour has already been performed by 
Engestrom, Bergman, Mongez, and others; 
