ON SPECIFIC GRAVITY. 
249 
for solids and liquids, and atmospheric air for gases. Solids are 
first weighed in air and then in water. The loss of weight arising 
from the action of the water is equal to that of the mass of the 
fluid possessing the same dimensions as the solid itself. If the 
solids are so light as to float upon the water, attach to them a heavier 
body, sufficient to cause it to sink, but the weight of which in 
water must be added in computing the loss. 
The following is requisite before we can proceed; viz. the 
specific gravity which holds, up to a mark in the neck, 1000 grains 
of distilled water, at the temperature of 60° Fahr. A brass weight 
generally accompanies the bottle that exactly counterpoises it when 
empty. A glass testing tube or a large tumbler, a thermometer for 
taking the heat, and a good balance are requisite. One of the pans 
should be suspended by much shorter strings than those attached 
to the other pan, and should have a small hook at the bottom from 
which any solid can be hung by a hair or a thin thread. 
Example 1. Hang a piece of lead by a thread to the hook, the 
weight taken in the air is 398 grains. A glass of distilled water 
is placed under that end of the scale-beam to which the lead is 
attached : the lead being immersed in the water, it weighs 362.4 
grains. Difference in air and water 35.6 grains, water being 
unity. 
Therefore, if 35.6 : 1 : : 398=11.176, the specific gravity of 
the lead. 
Example 2. A piece of wax weight in air is 105.4 grains. It 
floats on the surface of the water, therefore a piece of lead should 
be attached to the wax, and the two bodies weighed in the water 
together. 
The lead alone weighs 378 grains in water. With the wax 
attached to it the weightis 372.4 grains ; difference 5.6 grains, which 
being added to the weight of the wax in air makes 111 grains : 
then, if 111 : 1 : : 105.4n0.949, the specific gravity of the wax. 
Example 3. Of Powders. If 100 grains of calomel are put 
into the specific bottle of 1000 grains when the bottle is filled 
with water it then weighs 1083.7 grains : from this deduct the 
100 grains of calomel, there remains 983.7 grains, which subtract 
from the 1000grains=16.3. If 16.3 : 1 : : 100=6.03, the specific 
gravity of the calomel. When any powder is soluble in water, 
some other liquid in which it is not soluble may be used. 
Example 4. Of Liquids. The weight in grains of any fluid 
filling the 1000 grain bottle is the specific gravity at the tempe- 
rature of 60° Fahr. 
Spiritus rectificatus, spec. grav. .835 at 60° Fahr. Acidum 
sulphuricum, spec. grav. 1.850 ; equal bulks of these two 
liquids and distilled water possess weights in the proportion 
VOL. XVIII. M m 
