EXPERIMENT 1: SPECIFIC GRAVITY

Specific gravity

may be defined as the ratio of the mass of a substance to the mass of an equal volume of another substance taken as the standard.

hydrogen or air;

For gases

the standard may be

water.

for liquids and solids,

the standard may be

air or in a vacuum.

A difference in the result if the masses (weights) are determined in the???

True specific gravity

is used if the masses are determined in, or referred to, a vacuum.

absolute specific gravity

True specific gravity - sometimes called

Apparent specific gravity

– the calculated result if the masses are determined in air.

25°/25

the specific gravity basis is

which is solid at 25°

the specific gravity is determined on 100°/25° basis

Theobroma oil,

which is solid at ——

the specific gravity is determined on —— basis

15.56°/15.56°

Alcohol, it is determined on a

60°F (15.56°C)

Alcohol, it is determined on a 15.56°/15.56° basis because many years ago the US government adopted ————

• as the temperature at which alcoholometric measurements are to be made for government control of alcoholic liquids.

pycnometer

is a glass flask with a closefitting ground glass stopper with a capillary hole through it.

pycnometer

• A flask is made to hold a known volume of liquid at a specified temperature.

• The bottle is weighed, filled with the liquid whose specific gravity is to be found, and weighed again.

• The difference in weights is divided by the weight of an equal volume of water to give the specific gravity of the liquid.

• 1 mL to 50 mL.

A pycnometer is a special glass bottle used to determine specific gravity.

• Generally available for laboratory use in volumes ranging from ——

Carl Friedrich Mohr

The Westphal Balance was first described by German chemist??

• in 1832.

Mohr Westphal Balance

WESTPHAL BALANCE A.K.A.

WESTPHAL BALANCE

A direct-reading instrument for determining the densities of solids and liquids; a plummet of known mass is immersed in the liquid whose density is to be measured.

tray method

Modifications were made by the good Dr. Westphal who replaced a??

• with an adjustable arm counterweight

plummet (plumb)

To measure the density of liquids,

• WHAT placed in the vessel with the liquid to be determin ed, and the balance is equalized by a djusting the riders.

Archimedes' Principle of buoyancy

WESTPHAL BALANCE

The scale relies on WHAT PRINCIPLE

RIDERS

WESTPHAL BALANCE

counterweights sometimes called —-

• respectively signify the ones place of the specific gravity of the sample solution, the tenths place, the hundredths place, and the thousandths place.

WESTPHAL BALANCE

incapable of highly accurate density readings, as large temperature ranges in laboratories can affect is ability to duplicate results, and the alignment of its pointers is based on human sight and therefore full of potential for human error .

pycnometer

extremely accurate density readings one may prefer to use a???

HYDROMETER

• is an instrument used for determining the specific gravity of liquids.

• is usually made of glass and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright.

Archimedes’ principle

hydrometer is based on WHAT principle

• liquids heavier than water

• liquids lighter than water

Hydrometers can be divided into two general classes:

Heavy Hydrometer

TYPES OF HYDROMETER

• for liquids heavier than water.

Light Hydrometer

TYPES OF HYDROMETER

• liquids lighter than water