Revision as of 15:17, 28 June 2013

Determination of the color of waxes is important because this physical property is immediately observed by consumers. This physical property also serves as a control in the manufacturing and as an indicator of the degree of refinement of waxes. Since the range of color is known a variation outside the established range could be a guide for a possible contamination or to know when they have been refined to the required grade.

Methods

Aside from the Saybolt color method, colors of waxes are sometimes expressed in the terms of the Lovibond scale, or by the NPA color standard (Method ASTM D1500). These latter methods require matching the color with a colored slide. The Saybolt method employs discs of gray-colored glass, and is limited to the white and off-white waxes.

Saybolt Chronometer Method

Saybolt color is an empirical definition of the color of a clear petroleum liquid based on a scale of -16 (darkest) to +30 (lightest). The number is derived by finding the height of a column of the sample that, when viewed through the length of the column, visually matches the appropriate one three glass standards referring to Table 1 of Test Method D156 Switch the device on (colorimeter electrical system) from 20 to 30 minutes before use it. The wax sample is melted (when the sample is cloudy, filter through a paper filter), the heating of the sample must not be higher than 8 -17 °C above its congealing point (the sample can be oxidized if overheated). Secure the key is closed by rising the colorimeter bulb’ output key’ handle that contains or will contain the sample and turn the lamp on. Arrange the filters, the mirror and the lamp to see a clear field through the ocular. Pour the sample into the bulb until it is full but make sure you can see clear through the ocular field and the filter. Start pouring the sample, draining it through the key, slowly and observing through the ocular the sample and the filter. Stop the sample output, closing the key, when the sample looks the same in color intensity than the filter; make sure the lamp, mirror and standard filters are well positioned. If the sample does not equal at any moment in color the filter in use, change the filter (the colorimeter has 3 filters, one half filter, one filter and two filter, which are used depending on the color of the sample),and rerun. Make sure the sample does not last long in the bulb otherwise it could get burn or rust, changing of color, approximate maximum time duration 10 minutes. When the samples equals in color the filter, observe the reading mark by the meniscus of the wax in the graduated bulb. To end the procedure, the reading just made is searched in the table located in the back of the colorimeter, in the “Depth of oil In” section, the filter used in the column is verified in “Number of color standards”, and the final result color is searched in the “color number” column.

ASTM Color of Petroleum Products

Using a standard light source, a liquid sample is placed in the test container and compared with colored glass disks ranging in value from 0.5 to 8.0. When an exact match is not found and the sample color falls between two standard colors, the higher of the two colors is reported. The wax sample is melted to approximately 17°C above its congealing point, after this, place the sample in its container and introduce in the other compartment and cover the containers to exclude all light from exterior. Turn the light source on and compare the sample color against the pattern glasses ‘color.

Lovibond Color Method

Lovibond also known as degrees lovibond or abbreviated as L is a scale for measuring color originally introduced by Joseph Lovibond in the 1860's. To determine color the sample is placed in a "Tintometer" which also contains several numbered discs of tinted glass. The Lovibond color is the value assigned to the disc whose color most closely matches the sample. The original Lovibond scale was used to measure gas colors, but has since expanded to measure the colors of oils, chemicals, foods and beverages. Nowadays Lovibond is a Brand dedicated to de manufacture and distribution of water equipment and color test instruments.