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ISSUE NO. V1.3 DATE 12/12/00
12
Colour Scale
References
AOCS-Tintometer
Colour
AOCS Cc 13b-45 the Wesson Method,
AOCS Cc 8d-55, AOCS Cc 13j-97
ASTM Colour
ASTM D 6045, ASTM D 1500
Chlorophyll A & B
AOCS Cc 13d-55
FAC Colour
AOCS Cc 13a-43
Gardner Colour
ASTM D 1544, ASTM D 6166, AOCS Td 1a
IP Units
IP 17 Method B
Iodine Colour
DIN 6162
Klett Colour
AOCS Dd 5-92
Lovibond RYBN
AOCS Cc 13j-97, IP 17 Method A
Platinum-Cobalt/
Hazen/APHA Colour
ASTM D 1209, AOCS Ea 9-65, AOCS Td
1b-64
Saybolt Colour
ASTM D 6045, ASTM 156
5. Measuring a sample
When switched on, the operating parameters will be set to those selected when the instrument was last used. If appropriate, reselect
the colour scale and path length required (see
Setting the operating parameters
).
Performing a baseline measurement [ZERO]
It is necessary to take a baseline measurement before carrying out sample measurements and at intervals during prolonged use. The
baseline measurement calibrates the instrument on both dark and light values.
When performing a baseline measurement always
ensure that the sample chamber is empty.
The Lovibond PFX995/950 automatically takes a baseline measurement when it is first switched on. This measurement should be
repeated at least every 4 hours by pressing the
[ZERO]
key.
Sample preparation
Where the measurement is according to a standard test method (see
table), refer to the method for details of sample preparation. In
general, samples should be clear and not turbid as suspended
matter can cause scattering of the light beam, resulting in low
transmittance values, which do not correspond with the sample
colour.
Ensure that the end windows of the sample cell are clean and take
care to handle cells only by the sides. Allow viscous samples time to
settle, ensuring that air bubbles have dispersed and there is no
movement in the sample. When samples are measured at elevated
temperatures, the cell should also be heated to prevent the
temperature gradient from distorting the light beam. Stirring the
sample in the cell prior to measurement can help to create an even
temperature throughout the sample.
Taking a measurement
General instructions (see below for special instructions relating to specific colour scales)
After the baseline measurement is finished the instrument is ready for use.
Position the sample cell at the right hand end of the
sample chamber
. Insert the sample against the right-hand end of the sample chamber. Close the sample chamber lid and press the
[READ]
key.
Special instructions relating to specific colour scales
AOCS-Tintometer
Colour
Unless working to a test method that specifies the path length, the cell used should relate to the colour of the sample.
As a guideline, decrease the cell path length if the Red value is over 20 or if the Yellow value is greater than 50.
beta Carotene
Dilute the sample using a ratio of 1 gram of sample in 100 millilitres of spectroscopic grade cyclohexane. Carry out
the measurement in a 10 mm cell as per general instructions.
Chlorophyll A & B
Ensure that the path length is set at 10 mm as this value is used in the calculations for chlorophyll A & B.
FAC Colour
With melted fats, ensure that the sample is completely liquid. The sample should not be heated any higher than 10
degrees C above the melting point. Filter the sample if necessary.
Lovibond Colour
Unless working to a test method that specifies the path length, the cell used should relate to the colour of the sample.
As a guideline, decrease the cell path length if the Red value is over 20 or if the Yellow value is greater than 50.
Pt-Co/Hazen/APHA
Due to low absorption of samples, a baseline measurement should be carried out once every 2 hours.
Saybolt Colour
Due to low absorption of samples, a baseline measurement should be carried out once every 2 hours.
If the User ID option is enabled then the display will show:
User ID Backspace
^ ^ ^ ^
Enter the User ID code, and press
[
↵
↵↵
↵
]
to continue.
If the Sample ID option is enabled then the display will show:
Sample ID Backspace
^ ^ ^ ^
Enter the Sample ID code and press
[
↵
↵↵
↵
]
to continue.