Encyclopaedia Britannica > Volume 7, ETM-GOA

E U D [
Eudlowe- inches long, with a foot of glafs all made of one piece.
te!'- Within about an inch of the mouth of this tube a
kj-afs ,-;ng ;s fafteued, which contains two brafs rings
moveable upon oppofite centres, in the fame manner
that fea-compafies are ufually fufpended, and which
are commonly called gingles. C C C C reprefents the
meafuring tube or eudiometer; which is exadly the
fame with that already deferibed, having lines marked
upon its outfide furface to ihow .the fpaces occupied by
equal meafures of elaftic fluid. The fcale .5 i? is ad¬
apted to this tube, which is fhown’feparately in fig. 6.
It confifts of two brafs flips jIC, AC, conne&ed by
'two brafs rings A A, C C, through which the eudio-
•meter tube pafles. To the loweft of thefe rings a
■perforated brafs piece B £, furniflied with crofs pins
or pivots, is fere we d ; and, by means of longitudinal
cuts, its lower extremity is rendered fpringy ; Fo that
when all the piece AB is put upon the eudiome¬
ter tube, the latter cannot flip from within the former,
•unlefs the operator .forces it. When the eudiometer
tube, with the fcale, &c. is put together, as reprefented
fig. 5. the crofs pins of the piece B B, fig. 6. reft upon
the inner ring of the gingleat^y^, fig. 5. by which
means the tube C C C C is kept perpendicular within
the tube A A A A, provided this latter be fituated fo
nearly perpendicular that the former may not touch the
;fide pf it, which wamld prevent it from acquiring the
pofition defired. One of the brafs flips AC, fig. 6. is
divided into equal parts ; 100 of w'hich are equivalent
to the fpace between two of the marks on the eudi¬
ometer tube CCCC, fig. 5. and confequently ihow
the parts of a meafure. Thefe divifions are numbered
from the upper edge of the lower ring conncdling the
two brafs flips, AC, AC.
When this inftrument is to be ufed, one or more
meafures of refpirable air are thrown into the eudi¬
ometer tube; a meafure of nitrous air is then added ;
and after (baking the tube for fome time, it muft be
introduced into the large tube A AAA, which for this
purpofe muft be plunged into the water of the tub;
for the mouth of the eudiometer tube muft not at pre-
fent be taken out ,of the w'ater. After it has been
introduced into the large tube, the whole is taken out of
the water, and fet upon the ftielf or a table. Now the
large tube AAAA is filled with water, and the eudi¬
ometer tube fufpended perpendicularly in it by means
of the crofs pins or pivots of the brafs piece annexed
to the fcale, which refts upon the inner ring of the
gingle. The operator muft then Aide the tube CCCC
up and down through the fcale and brafs piece, 8cc.'
till’the furface of the w'ater within the tube coincides
exa&ly with the upper edge of the lower ring that con-
neds the two brafs flips of the fcale piece, which may
he done very accurately by means of a magnifying
glafs. The furface of the water within the eudiome¬
ter is concave; and when viewed horizontally, it ap¬
pears like a dark line or limit exceedingly well de¬
fined ; fo that the middle or lowermoft point of it
may be made to coincide with the edge of the brafs
ring with great precifion, except when fome drops of
water hang on the outfide of the tube, which fhould
therefore be wiped off.
Having afeertained this point, we muft next obferve
which diviiion of the fcale coincides with one of the
circular divifions marked upon the glafs.tube CCCC,.
23 ] E U D
which will fhow the parts of a meafure. Thus fup- Eudiome-
pofe, that when the eudiometer tube is fixed, fo that, ter- ,
the furface of the water in it coincides perfectly with *
the edge of the lower brafs ring, viz. with the begin¬
ning of the divifions ; that the 70th divifion of the
fcale falls upon the firft circular mark, as reprefented
in the figure ; then it is plain, that the quantity of
elaftic fluid contained in the tube is equal to one mea¬
fure and 70 hundredth parts more. This being obferved,
and the large tube again immerfed in the water, the
eudiometer-tube is removed from it, but always taking
care that its mouth be not lifted up above the furface
of the water. Another meafure of nitrous air muft now
be introduced into the eudiometer-tube ; which, after
being agitated as already diredted, is to be put into the
large tube AAA A. The whole is then taken out of the
water, and the diminution of the elaftic fluid obferved
as above diredted.
Thus the eudiometer tube is kept quite perpendicular,,
and the pillar of water in it rendered very fhort, not
exceeding half an inch at moil. It is eafy to perceive,
'.however, that if the operator, when furniflied with the
eudiometer-tube only, keeps it fo far immerged in the
water of the tube when he obferves the divifions, that
the water within the tube may be nearly equal with the
edge of the tub ; the large tube AAAA may be fpa-
red, and the operation will thus become much more
ealy and expeditions. Little difference can happen from
the pofition of the tube; becaufe the brafs ring afeer-
tains the pofition of the water fo well, and the diffe¬
rence occafioned by a few degrees deviation from the
true perpendicular is fo fmall, that it can fcarce be per¬
ceived.
VI. M. Sauffure of Geneva has invented an eudio-j^ g/up
meter, which he fuppofes to be more exadf than any fare’s eudj»
of thofe hitherto deferibed. His apparatus confifts of ometer.
the follow ing parts, j . A cylindrical glafs- bottle with
a ground ftopple, capable of containing about five
ounces and an half, and w'hich ferves as a receiver for
mixing the two airs. 2. A fmall glafs phial, whofe capa¬
city is nearly equal to one third of that of the reci-.
pient, and ferves for a meafure. 3. A fmall pair of
feales w'hich may weigh very exadfly. 4 Several glafs
bottles for containing the nitrous or other air to be
ufed, and which may fupply the. place of the recipient
when broken. The whole of this apparatus may be
eafily packed into a box, and thus tranfported from
place to place, and even to the fummits of very high
mountains. The method of ufing it is as follows.
1. The receiver is to be filled with water, clofed ex¬
actly with its glafs Hopper, wiped on the outfide, and./
weighed very exadtly. Being then immerged in a veL
fel full of water, and held with the mouth downwards,,
the ftopple is removed, and, by means of a funnel,
two. meafures of common and one of nitrous air are
introduced into it one after another : thefe diminifh as
foon as they come into contaft; in confequence of which
the water enters the recipient in proportionable quan¬
tity. After being flopped and well fhaken, to pro¬
mote the diminution the receiver is to be opened un¬
der water; then flopped and (haken, and fo on for
three times fucceflively. At laft the bottle is flopped
under water, taken out, wiped very clean and dry, andi
weighed exaftly as before. It is plain, that now when
the bottle is filled partly with elaftic fluid and partly
witfi'i