The prison mirror. [volume] (Stillwater, Minn.) 1887-1894, 1890-10-30
SPECIFIC GRAVITY.

Take any solid substance and immense it in
water and 1t will be found to displace volume
exactly equal to its own bulk and also at the same
time lose portion of its weight just equal to
the volume of water displaced. Thus water found
every where and easely purified is taken the
unit of comparison for solids and liquids. The
bulk of bodies is sometimes altered by variations
of temperature. for that reason specific gravity
is taken at the standard of 60 degrees. To find
the specific gravity of any solid substance fill a
vessel with water and drop into it piece of sui
phur weighing say o.. having glass SO set that
the water escaping from the vessel will flow into
the glass below. On dropping the sulphur into the
larger vessel quantity of water will escape into
the smaller glass. equal to the bulk of the sulphur
Next weigh the water in the small glass and it
will be found to weigh n Thus the sui
pher weighs twice much equal volume
of water and its specific gravity is 2. The plan
to suspend the solid to the scale pan of fine bal
ance by fine thread or hair. then counterpoise it
and thus get its weight in air. lmmerse the sus-
pended body in a vessel of distilled water remove
the weights until the last equipose is obtained.
Now divide the original weight in air by the loss
in water and the quotent IS the specific gravity of
the substance weighed. To find the specific gray
ity of liquids procure small bottle and make
fine mark upon its neck you then have a specific
gravity bottle. counterpose it in the balance. fill
to the mark with distilled water 60 degrees and
weigh it, then empty the bottle, and fill it with
the liquid the specific gravity of which desired.
Its weight divided by that of the water gives the
desired result. In practice a bottle holding 1000
or LOG grains of distilled water at 60 degrees is
generally used, thus saving calculation. For
instance, the bottle holds 1000 grains of pure
water, it will be found to hold 1916 grains of sui
phufic acid which therefore has "a specific gravity
1S45.
The specific gravity of gases is obtained in a
like manner. flask or globe is weighed when
empty and again when filled with air. This gives
the weight of the air which is taken as a unit
Other gases then changed for the air and their
comparative weights ascertained. Gases vary in
density, caused through alterations of tempera-
ture and atmospheric pressure. These weights
are taken at barometric pressure of thirty
inches. The specific gravity of soil or any other
powder is obtained by Contemplating 1000 grain
bottle and weighing into it $50 grains of SOIL
partially fill with water. shake WE'LL as in putting
an the soil certain quantity of air was also put
in with the soil. Having shaken we'll fill with
water and weigh. The total is, say 1,O96 grains
$50 are soil and GAG water. Therefore 81 grains of
water have been displaced by $50 grains of SOIL The
calculation is then easy. Specific gravity is then
shown to be one of the most important of the phys
ical properties of bodies. Its laws are like the
laws of all sciences. hard and difficult. but by a
constant and energetic study of them we. like
Tennyson, will be able to say
Here about the beach wandered, nourshing a
youth sublime
With the Fairy Tales of Science and the long
result of time SECRETARY