Spirit of the age. [volume] (Woodstock, Vt.) 1845-1913, 1871-09-14
Steam Boiler Waters and Incrustation.

DR.. Joseph G. Rogers of Madison,
Indiana, in n paper on steam boiler water
and incrustation, to the American Scien-
tifc Institute, said that practical men
have always felt the need for scientific
information on this important subject.
They have made inuumerable attempts to
overcome the difficulties attending the
use of hard water-yet so crude and
superficial have they been that but little
success has been attained. What follows
is brief resume of the various proposed
methods, together with some investiga-
tons of my own.
All natural waters contain in solution
or suspension more or less mineral matter
and vegetable matter This consists
principally of the carbonates of lime,
magnesia and iron (held in solution by
free carbonic acid, sulphates of lime and
magnesia, chlorides of calcium, sodium
and magnesia, and undissolved carbon
ates, clay, sand and vegetable matter,
held in suspension. Spring and well
waters contain a larger amount in solu-
ton than rivers, lakes, &C. The latter
hold more i'll suspension. Our American
rivers, contain from 2 to 10 grains in
solution, and varying quantity in sus-
pension generally exceeding 10 grains
Well and spring waters contain but
little in suspension, but a quantity of the
dissolved salts varying from 10 to $50
grains. These latter cause what is gen
orally known as hardness. When these
waters are boiled the carbonic acid is
driven off, and the carbonates of the
alkaline earth deprived of their solvent
are precipitated in finely crystalline
form, which tenaciously adheres to what
ever it may fall upon. Sulphate of lime
is only soluble in 500 parts of water, and
is precipitated by approximation after
further evaporation. The suspended
matter gradually subsidies and forms
additional increment to the deposit.
This gradually accumulating grows hard
and tough like porcelain, and may attain
an unlimited thickness. The evil effects
of scale are due to the fact that it is
relatively non-conductor of heat. Its
conducting power compared with that of
iron is as l to 37.5. This known, it is
readily appreciated that more fuel is
required to heat water through scale and
iron than through iron alone. 1t has
been demonstrated that scale 1-16 of an
inch thick requires the extra expenditure
of Is per cent. more fuel. AS the scale
thickens the ratio increases-thus when
it is / inch thick, GO per cent. more is
required at inch, 100 per cent and so
on. TO raise steam to working pres
sure of 80 pounds, the water must be
heated to 1902 Fair. This may be done
through inch iron shell by heating
the external surface to about 1850. If a
inch scale intervenes the boiler must
be heated to 1000, almost low red heat.
The higher the temperature at which
iron is kept the more rapidly it oxidizes,
and at any temperature above 6OOo it
soon becomes granular and brittle from
carbonization or conversion into the state
of cast iron Weakness of boiler thus
produced predisposes to sudden explo-
sions, and makes expensive repairs neces-
sary.
After detailing several processes for
the removal and prevention Of scale by
chemical means operating inside the
boilers, the writer preferred the follow
ing In this method the tannate of soda
is the essential element. This may be
cheaply prepared, and is attainable
generally. This agent being introduced
into the boiler at regular intervals in
sufficient quantity, according to the
hardness of the water, is rapidly dis
solved. and, without foaming or action
on the iron, completely does the desired
work. The reaction is as follows The
fannie acid leaves the soda and combines
with the lime of the carbonates to form
tannate of lime, which is precipitated in
light, focculent, amorphous form, which
does not subside in the boiler at all, but
floats in the currents of ebulition, till it
finds its way to the mud-receiver, where,
as there is little or no current, it is de-
posted as mushy sediment, which may
be readily blown out from time to time.
The sulphate of lime is decompoSed by
the carbonates of soda formed by the
first reaction, soluble sulphate Of soda
and carbonates of lime being formed.
The latter is converted into tannate of
lime by fresh portions of the tannate of
soda. The pre-existing scale is more
slowly disintegrated, and the resulting
tannate of lime voided as before de-
scribed. The presence of the alkaG
prevents all action of the acid on the
iron. Extensive practical trial of this
method has demonstrated its utility IN
all kinds of boilers, and its perfect eff
cacy, safety, economy, ease of applica-
ton, and general adaptability, will COM
mend it for general use.