SUBLIMING VESSELS, &c. 
300 
termediate vessels are found indispensably necessary. Mr. Peter 
Woulfe, F. R. S. has contrived an apparatus for those difficult distil 
lations, which, by proper modifications, will obviate every difficulty. 
A particular description of this apparatus would take up much of our 
time, and therefore I refer you to Phil. Trans. vol. 57. p. 517. 
After, or during some distillations, we have occasion to make use of a 
SEPARATORY, which is a glaſs veſſel, of a tall form, having a ſpout riſing 
from nearly the bottom, and rather exceeding the vessel in height. It 
is plain that by this contrivance, the lower parts can be poured off, 
without disturbing or being disturbed by the upper parts. 
For fublimation, the vessels employed are sometimes the cucurbit 
and capital, because, in many sublimations, some liquor comes before 
the dry matter sublimes. But in such cases, we more commonly use a 
retort with a wide and ſhort neck, and a receiver; for which purpose 
the conical form is much the best. For particular purposes we use an 
oblong or spherical glass vessel,—a Florentine flask, or even a common 
phial ; and sometimes the aludels, or allodials, which resemble the 
antique receivers which are mentioned above, are used in a feries. 
Having now finiſhed the list of vessels which are employed in che 
mical operations, there only remain to be mentioned those necessary 
for the preservation of many of the products of chemistry. Many of 
thoſe products are volatile, and require to be ſhut up closely in vessels. 
Others are affected by the humidity of the air; and it happens, at the 
fame time, that many of them are very corrosive, and destroy com 
mon corks. Such can be preserved, therefore, only in glass vessels, 
with glass stoppers, that ſhut them close; and a number of such phials 
are necessary. 
It is also proper to fubjoin to the enumeration of the vessels, the 
mention of a means by which we alter them on some occasions, by 
cutting off parts of them to fit them better to our purpose. This is 
done by an iron knife or rod made red hot. A small scratch being 
first made on the edge of the glass, the red hot knife is applied there,