834 / 1042
H Y D
n o s
T A T
e s,
fpeaive hulks of
comm~n
pump water, whieh is genmlly
made aflandard for eomparing a11 the others by.
In eonflruaing tahles of fptcific gravities with accuracy,
the gravity of water mul! be reprefented by unity or
1.000,
wh~re
three cyphers are added, to give room for
exprelling the ratios of oth=r gravities in decimal pans,
as in the following table.
T ake away the decim,1point from tbe numbers in the
right hand column, or (which is the fame) muhiply them
by 1000, and Ihey willlhew holV many ounees avoirdu–
poife are contained in a eubic foot of eaeh body.
H()1J)
fD
jnd
Duf
Ih(
quanlil,
of
adullualion in m(la/¡.
THEufe ofthetableof fpecific grav;ties will bcfl appear
by an example. Suppofe a body 10 be compounded of
of gold and filver, and it is required to 6nd the quantity
ofeach melal in the compound.
Firn find Ihe fpeeific gravity of the compound, by
weighing it in air and in waler, and dividing its aerial
weight by what it lofes Ihereof in \\ aler, the quotient
willlhew ils fpecific gravity, or how many times it is
heavier than its bulk of water. Titen, fubtraa Ihefpe–
cific gravity of' filver (found in the table) from that of
the compound, and the fpecific gravily
oE
,Ihe com–
pound from that
oE
gold; the firfl remainder lhews,the
bulk
oE
gold, and Ihe latter the bulk of filver, in the
whole compound: and if theCe remainders be multiplied
by the refpeaive Cpecific gravities, the produas willlhew
the proponion of weightsof each metal in the body.
El{–
ample.
SuppoCe the Cpeei6e gravity of Ihe compoondtd boJy
to be 13
j
Ih,tt of fbodard filver (by the table) is 10. S,
and tb.1of gold 19.63 : therefore 10,5 from 13, remaios
2.
5, the propunional bulk of the gold'; and 13 from
19,63, remaios 6.63, the proponiODaI bulk of film iD
the compound. Then, the firfl remainder 2,5, muhi–
plied by 19.63, the fpecific gravily of gold, produces
49.075 for the proponional weighl of gold; and Ihelafl
remainder 6.63 OIuhiplied by 10.5, the Cpeci6c gravilyof
filver, produces 69.615 for the proponioDal weight of fu–
ver iD Ihe whole body. So that, for e,ery
49.07
ounees
or pounds of gold, there are 69.6 pounds or ounces
oC
filver in t'he body.
Hence it is eaCy to know whether any CuCpeacd metal
be genuine, or allayed, or counlerfeit; by finding holV
muclt it is heaviep lhan its bulk of water, and comparing
the fame wilh the table: if they agree, themetal is good'
if Ihey difIer, it is allayed Dr counterfeited.
'
HO'UJ
lofr,fpirilu,ul/.'qum.
.~ CUB~CAL
ioch of
~ood
brandy, ru?" or olher proof
fptrtls, welglts 235 .7gtatns; thererore, tf a!rue inch cube
of any metal weighs 235.7 graios lefs in fpirilS thao in
air, it ./hews the fpiril! are proof, lf il lofes lefs of il!
aerial weigbt in fporiti, theyare above proof: ifit !ofes
more, tbey aré under. For, Ihe bCtler the fpirits are,
they are the lighler; and the worfe, the heavier.
The hydrometer is one of the mofl ufeful inllrumenta
of
the philofophic kind; for though the hydrollatical
balance be the mofl general inllruruent fo[ finding
the
A
T
ULE
of the fpecific Gravities orthe reveral folid aDd Huid Bodies.
Troy weigh!
Avoirdllp. Compa-
A cubic ineh of
-----
-----
ralive
oz. pw,
gr. oz. drams . wcight.
Very fine gold
--
lO
?
3. 83
1 5 80
19.637
Standard gold
--
9 19 6'44
10 149 0 18.888
Guinea gold
---
9
?
17 18
10 47 6 17<793
Moidorc gold
--
9
o
19.84 9 14.71 17.140
~ickfilver
--
7
?
11.61
8 1.45
14. 01 9
Lead
--
--
5 19 17·55
6 9.08
11
32 5
fine film
---
5 16 23 .23 6 6.66
1108 7
Slandard filver
--
5
11
3.3 6 6 1·54
10·53 5
Copper
--
--
4 13
?
04
5 1.89
8.843
Plale braCs
--
4 4 9.60
4 10.09
8 000
Sleel
--
--
4
2
20.12
4
8.70
7.852
lron
--
--
4
o
15- 20
4 6·77
7.6
.)5
Block tin
--
3 17
5 68
4 3·79
7.321
Spclter
-
--
3 14 12.86 4 1.4
2
7 06 5
Lead ore
--
3
11
17 76
3
IH6 6.800
Glafs of antimony
--
2 15 16.89
3 0.89
5. 280
German antimony
- -
2
2
4.80
2 5.04
4 000
Copper ore
--
2 1 II .S3
2 4' 43
3·775
Diamood
--
- -
1 15 20.88
1 15048
3 4°0
Clear glafs
--
1 13 5.58
1 13 16
3.15 0
Lapi! lazuli
--
I 12
5027
1 12.27
3.0 54
¡Wdeh albcRos
--
I 10 17· 17
1 10·97
2.913
1ht