, 1881-05-04

Steam having been turned on as above
mentioned the liquor will shortly be in full
boil, as can be seen through the peep glass
though the temperature. as shown by the
thermometer is only 40 to 1900 Fab.
instead of 23Oo at which syrup will boil in
the open air. AS is known, a liquid bolls
at a lower temperature when the atmos-
pheric pressure has been wholly .sor partly
removed, because. as it bOllS, the elastlc
force of it's yapour becomes greater than
the pressure exerted on it's surface, and,
as the elasticity of the vapour Of all H.
guilds is increased by q rise of temperature
it is plain that such will boil at a lower
temperature in a vessel from which The
air pressure has been removed, because
the point at which the tension OF the
vaponrs will exceed the remaining pres
sure on them, will be sooner reached.
The degree of vacuum is regulated dur
ing the boiling by the injection cock. The
wider this cock is opened so much the more
water goes into the condenser, consequent
" from the quicker condensation OF the
steam. the thermometer falls. 1t is custo'
mary to boil syrup with 1926 inches Vacu'
um as shown by the guage when the
temperature will be between 600 and 65o
Fab. If syrup is being boiled Tor mus
coyadO sugar in an open copper, the
WuOlO QuduUlpN w NO OOlON~ 49,
be, put in and concentrated at once with
out any more liquid being added to it after
it begins to get thick for, if to get a
larger quantity of sling in the copper,
further additions of syrup are added, the
first part put in would be too long expos
ed to the high temperature, and conSe-
quently lose a great part of it's crystalllsa-
bic power This consideration however
does not hold good when boiling in vacuum,
because the low temperature OF the boiling
syrup greatly lessons the danger OF q
disastrous change in it's saccharine proper
ties, and, therefore, there is no harm IN
adding more syrup in the vacuum pan to
that originally admitted and decreased by
concentration
While the syrup in the pan is thin, the
waves it makes in boiling are high and
sharp, and pitch about lightly and frothl-
ly; but as it gets more concentrated they
become heavier and less lively, all OF
which can be distinctly followed through
the glass. The timo now approaches
when by means of the ''proof-stick" the
boiler begins to try the stoutness of the
pans contents, !. o., to see whether it's
degree of viscidity shows that it has been
so much reduced that sugar il ready to
crystallise out. Before proceeding to this
point however, | must say a few words
aboutsthe previous boiling down OF the sy-
rup to this degree af concentration. 1t is
customary to draw into the pan as much
syrup, as will cover the bottom coil latter
having been reduced by concentratlon),
this is called "graining low down )" some
pan boilers prefer to grain high up, and
some when the pan is half full. The OBJ.
lection to granting high mp is, that the
grain has not SO much time to grow IN
size, and this is avery sound objection. but,
does not. from the shape and interior con.
struction of the pan, always hold good. fla
vacuum pan take say seven hours to boil
asstrike of eight tons apaSse.cuite, and was
grained low down, it will only take six
hours to boil similar quantity, if grained
high up; the crystals in the second
case will not be so big as in the
first; but in q large eight ton pan they
will be of a fair size, even by the quicker
method. 1T sometimes happens, though
not often, and this, although [ cannot give
good reason for it, is we'll known and
appreciated by pan boilers, that sugar of
a larger crystal and better quality can be
made III some pans by high than by low
granting. oIS knew of a pan in which for
long time good sugar was rot made,
until pan boiler at the suggestion of the
engineer tried granting high up, and the
sugar, then turned out, was very satistac-
ory, the sam man afterwards tried grain
10 low down in this pan and was most
1successful. The reason for this is pro-
bly, to be found in the position of the
Is. bnt this explanation to my mind is