TABLE 11.41 Pipet Capacity Tolerances

11.104

SECTION 11

TABLE 11.44

Factors for Simplified Computation of Volume

The volume is determined by weighing the water, having a temperature of

t C, contained or delivered by the

apparatus at the same temperature. The weight of water,

w grams, is obtained with brass weights in air having

a density of 1.20 mg/mL.

For apparatus made of soft glass, the volume contained or delivered at 20

C is given by

20 w

ƒ20 mL

where

20 is the volume at 20

and ƒ

20 is the factor (apparent specific volume) obtained from the table below for

the temperature

t

at which the

calibration is performed. The volume at any other temperature

t may

then be

obtained from

20[1 0.00002(t 20)] mL

For apparatus made of any other material, the volume contained or delivered at the temperature

t

is

t wf

t mL

where

w is again the weight in air obtained with brass weights (in grams), and

ft is the factor given in the third

column of the table for the temperature

t. The volume at any temperature

t may then be obtained from

t t[1 (t t)] mL

where is the cubical coefficient of thermal expansion of the material from which the apparatus is made.

Approximate values of

for some frequently encountered materials are given in Table 11.45.

t, C

ƒ 20

ƒt

t, C

ƒ 20

ƒt

0

1.001 62

1.001 22

20

1.002 86

1.002 86

1

54

16

21

1.003 05

1.003 07

2

48

12

22

26

30

3

43

09

23

47

53

4

41

09

24

69

77

5

1.001 39

1.001 09

25

1.003 93

1.004 0

6

40

12

26

1.004 17

29

7

42

16

27

42

56

8

45

21

28

68

84

9

50

28

29

95

1.005 13

10

1.001 56

1.001 36

30

1.005 23

1.005 43

11

63

45

31

1.005 52

1.005 74

12

72

56

32

1.005 82

1.006 06

13

82

68

33

1.006 13

1.006 39

14

93

81

34

1.006 44

1.006 72

15

1.002 06

1.001 96

35

1.006 77

1.007 0

16

20

1.002 12

36

1.007 10

1.007 42

17

35

29

37

1.007 44

1.007 78

18

51

47

38

1.007 79

1.008 15

19

68

66

39

1.008 15

1.008 53

40

1.008 52

1.008 91

PRACTICAL

LABORATORY INFORMATION

11.105

TABLE 11.45

Cubical Coefficients of Thermal Expansion

This table lists values of , the cubical coefficient of thermal expansion, taken from “Essentials of Quantitative

Analysis,” by Benedetti-Pichler, and from various other sources. The value of

represents the relative increases

in volume for a change in temperature of 1

C at temperatures in the vicinity of 25

C, and is equal to 3

, where

is the linear coefficient of thermal expansion. Data are given for the types of glass from which volumetic

apparatus is most commonly made, and also for some other materials which have been or may be used in the

fabrication of apparatus employed in analytical work.

Material

Glasses

Alkali-resistant, Corning 728

1.90

5

10

Gerateglas, Schott G20

1.47

Kimble KG-33 (borosilicate)

0.96

N-51A (“Resistant”)

1.47

R-6 (soft)

2.79

Pyrex, Corning 744

0.96

Vitreous silica

0.15

Vycor, Corning 790

0.24

Metals

Brass

ca.

5.5

Copper

5.0

Gold

4.3

Monel metal

4.0

Platinum

2.7

Silver

5.7

Stainless steel

ca.

5.3

Tantalum

ca.

2.0

Tungsten

1.3

Plastics and other materials

Hard rubber

24

5

10

Polyethylene

45– 90

Polystyrene

18– 24

Porcelain

ca.

1.2

Teflon (polytetrafluoroethylene)

16.5

TABLE 11.46

General Solubility Rules for Inorganic Compounds

Nitrates

All nitrates are soluble.

Acetates

All acetates are soluble; silver acetate is moderately soluble.

Chlorides

All chlorides are soluble except AgCl, PbCl

2 , and Hg

2 Cl 2 . PbCl 2 is soluble in

hot water, slightly soluble in cold water.

Sulfates

All sulfates are soluble except barium and lead. Silver, mercury(I), and cal-

cium are only slightly soluble.

Hydrogen sulfates

The hydrogen sulfates are more soluble than the sulfates.

Carbonates, phosphates,

All carbonates, phosphates, chromates, and silicates are insoluble, except those

chromates, silicates

of sodium, potassium, and ammonium. An exception is MgCrO

4

which is

soluble.

Hydroxides

All hydroxides (except lithium, sodium, potassium, cesium, rubidium, and am-

monia) are insoluble; Ba(OH)

2 is moderately soluble; Ca(OH)

2 and Sr(OH)

2

are slightly soluble.

Sulfides

All sulfides (except alkali metals, ammonium, magnesium, calcium, and bar-

ium) are insoluble. Aluminum and chromium sulfides are hydrolyzed and

precipitate as hydroxides.

Sodium, potassium,

All sodium, potassium, and ammonium salts are soluble. Exceptions:

ammonium

Na

4 Sb2 O

7 , K2 NaCo(NO

2 )6 , K2 PtCl 6 , (NH 4 ) 2 PtCl

6

, and (NH

4 )2 NaCo(NO

2 )6 .

Silver

All silver salts are insoluble. Exceptions: AgNO

3

and AgClO

4 ; AgC

2 H 3 O 2

and

Ag

2 SO

4

are moderately soluble.