BrandTech Scientific EASYCAL 4.0 - Manual (Page 27)

EASYCAL ™ User Guide Version 4.0 · Status: June 2008 27
EASYCAL
™
User Guide
7.3 Calculations for Glass/Plastics
Example:
Serial No: 95 080634
Trademark: BLAUBRAND ®
Type of instrument: Standard volumetric flask
Calibration: “IN” (to contain)
Nominal capacity/subdivision: 100 ml
Error limit: ± 0.1 ml
Testing temperature: 23 °C
Material: DURAN ®
Customer-specific marking: Test Lab FT
Empty weight of weighing vessel: W1 = 25.456 g
Weight of filled volumetric flask: W2 = 125.124 g
Factor “Z” from Table 1, medium atmospheric pressure range, since capacity of volumetric flask
≤
250 ml:
z
23 °C, DURAN
® = 1.00348 ml/g
V
20
= (W
2
- W
1
) × z = (125.124 g - 25.456 g) × 1.00348 ml/g
= 100.01 ml
Factor “Z”
The factor “Z” incorporates the following parameters:
■ Density of the calibration weight of the balance (ρ
G
):
☞ 8 g/ml (see specifications provided by the balance manufacturer)
■ Density of air in relation to atmospheric pressure, temperature and relative air humidity
of 40 – 90% (
ρ
L
):
☞ For all volumetric instruments (except volumetric flasks > 250 ml) the influence of atmospheric pressure in
relation to the stated error limits is relatively small. Therefore, Factor “Z” should generally be read from the
table “Medium atmospheric pressure range”. For volumetric flasks > 250 ml, select the appropriate table
for lower, medium or upper atmospheric pressure range, according to the present conditions. To determine
the appropriate table, measure the atmospheric pressure, or inquire at a local metereological station! (The
atmospheric pressure, related to sea-level, has to be couverted into local level.)
■ Density of water in relation to temperature (ρ
W
)
■ Cubic expansion coefficient of the volumetric instrument in relation to its material:
☞ DURAN ® :
γ = 9.9 × 10 -6 °C -1
☞ AR-Glas ® : γ = 27 × 10 -6 °C -1
☞ PP: γ = 450 × 10 -6 °C -1 (Manufacturer’s information, average value of
γ = 300 × 10 -6 °C -1 to γ = 600 × 10 -6 °C -1 )
☞ PMP: γ = 351 × 10 -6 °C -1 (Manufacturer’s information: Mitsui)
☞ Liquid Handling: (by definition) = 1
Factor “Z” takes the following parameters into account: