2.66

SECTION 2

The following abbreviations are used:

F, degrees

Fahrenheit;

C,

degrees Celsius;

K, degrees

Kelvin;

Re ´, degrees Reaumur;

R, degrees Rankine;

Z, degrees on any scale; (fp)“Z”, the freezing

point of water on the Z scale; and (bp)“Z”, the boiling point of water on the Z scale. Reference:

Dodds,

Chemical and

Metallurgical Engineering

38:

476 (1931).

F

32

C

Re ´

K

273

R

492

Z (fp)“Z”

180

(fp)“Z”

100

80

100

180

(bp)“Z”

Examples

(1)

To find the Fahrenheit temperature corresponding to

20 C:

F 32

C

or

F 32

20

180

180

100

100

F

32

( 20)(180)

36

100

F 4

(2)

To find the Reaumur temperature corresponding to 20

F:

F 32

Re ´

20 32

Re ´

180

80

180

80

i.e.,

20 F 5.33Re ´

(3) To find the correct temperature on a thermometer reading 80

C and that shows a reading of

0.30 C in a melting ice/water mixture and 99.0

C in steam at

760 mmpressure of mercury:

C

Z

(fp)“Z”

80

( 0.30)

100

(fp)“Z”

99.0 ( 0.30)

(bp)“Z”

i.e.,

C

80.87

(corrected)

2.1.2 Density and Specific Gravity

2.1.2.1

Hydrometers.

Various hydrometers and the relation between the various scales.

Alcoholometer.

This hydrometer is used in determining the density of aqueous ethyl alcohol

solutions; the reading in degrees is numerically the same as the percentage of alcohol by volume.

The scale known as Tralle gives the percentage by volume. Wine and Must hydrometer relations

are given below.

Ammoniameter.

This hydrometer, employed in finding the density of aqueous ammonia solu-

tions, has a scale graduated in equal divisions from 0

to 40 . To convert the reading to specific

gravity multiply by 3 and subtract the resulting number from 1000.

Balling Hydrometer.

See under Saccharometers.

Barkometer or Barktrometer.

This

hydrometer, which is used in determining the density of

tanning liquors, has a scale from 0

to 80 Bk; the number to the right of the decimal point of a

specific gravity reading is the corresponding Bk degree; thus, a

specific

gravity of 1.015

is

15 Bk.

GENERAL INFORMATION,

CONVERSION TABLES, AND MATHEMATICS

2.67

Baume

´ Hydrometers.

For liquids heavier than water: This hydrometer was originally based on

the density of a 10% sodium chloride solution, which was given the value of 10

, and the density

of pure water, which was given the value of 0

; the interval between these two values was divided

into 10 equal parts. Other reference points have been taken with the result that so much confusion

exists that there are about 36 different scales in use, many of which are incorrect. In general a

Baume

´ hydrometer should have inscribed on it the temperature at which it was calibrated and

also the temperature of the water used in relating the density to a specific gravity. The following

expression gives the relation between the specific gravity and several of the Baume

´ scales:

Specific gravity

m

m Baume

´

m 145 at 60

/60 F (15.56 C)

for the American Scale

For liquids lighter than water: Originally the density of a solution of 1 gram of sodium chloride

in 9 grams of water at 12.5

C was given a value of 10

Be ´. The scale between these points was

divided into ten equal parts and these divisions were repeated throughout the scale giving a

relation which could

be expressed by the formula: Specific gravity

145.88/(135.88 Be ´),

which is approximately equal to

146/(136

OtherBe ´)scales. have since come into more general

use such as that of

the Bureau

of Standards in which the specific gravity

at 60

/60 F

140/(130 Be ´) and that of the American Petroleum Institute (A.P.I. Scale) in which the specific

gravity at 60

/60 F

141.5/(131.5 API

).

See also special table for conversion to density and Twaddell scale.

Beck’s Hydrometer.

This hydrometer is graduated to show a reading of 0

in pure water and a

reading of 30 in a solution with a specific gravity of 0.850, with equal scale divisions above and

below these two points.

Brix Hydrometer.

See under Saccharometers.

Cartier’s Hydrometer.

This hydrometer shows a reading of 22

when immersed in a solution

having a density of 22

Baume

´ but the scale divisions are smaller than on the Baume

´ hydrometer

in the ratio of 16 Cartier to 15 Baume

´.

Fatty Oil Hydrometer.

The graduations on this hydrometer are in specific gravity within the

range 0.908 to 0.938. The letters on the scale correspond to the specific gravity of the various

common oils as

follows:

R

,

rape; O , olive; A , almond;

S , sesame;

HL

, hoof oil;

HP , hemp;

C ,

cotton seed; L , linseed. See also Oleometer below.

Lactometers.

These hydrometers are used in determining the density of milk. The various scales

in common use are the following:

New York Board of Health

has a scale graduated into 120 equal parts, 0

being equal to the

specific gravity of water and 100

being equal to a specific gravity of 1.029.

Quevenne

lactometer is graduated from 15

to 40

corresponding to specific gravities from

1.015 to 1.040.

Soxhlet

lactometer has a scale from 25

to 35 corresponding to specific gravities from 1.025

to 1.035 respectively.