c. of brine contains 10 grams of
salt, and is diluted with water to 200 c.c., it would be of one-half the
former strength, that is, 100 c.c. of the solution would contain 5 grams
of salt.
This confusion is avoided by always stating the strengths as so many
grams or "c.c." in 100 c.c. of the liquid. But obviously it would be
advantageous to be able to determine quickly the weight of any
particular substance corresponding to 1 c.c. or some other given volume.
Moreover, in descriptions of processes the strengths of acids and
solutions are frequently defined neither by their gravimetric nor
volumetric composition, but by a statement either of specific gravity or
of the degrees registered by Twaddell's or Beaum?'s hydrometer. Thus, in
the description of the process of gold parting, one writer gives: "The
acid should be of 1.2 specific gravity"; and another says: "The acid
must not be stronger than 32° Beaum?."
These considerations justify an account of the subject in such a work as
this. And on other grounds the determination of a specific gravity is
one of the operations with which an assayer should be familiar.
The meaning of "specific gravity" is present in the mind of every one
who uses the sentence "lead is heavier than water." This is meaningless
except some such phrase as "bulk for bulk" be added.
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