Colorant testing reporting results

To each test tube, add 10 drops of concentrated HN03 while swirling. Heat the test tubes carefully in a warm water bath. Observe any change in color. Record the results on your Report Sheet. 

The appearance of water, especially textile wastewater is systematically described in terms of its visible characteristics (Standard Methods, 1998). In this regard, the presence of color, suspended particles and turbidity is the focus of much of the testing conducted. In the case of textiles, the presence of color in wastewater is extremely important and numerical methods are normally employed to report results from making color assessments. While color in textile wastewater may arise from the presence of transition metal ions, vegetable matter and industrial plant effluents, color derived from unspent dyebaths is of primary importance. Invariably, this color is removed using a number of physical and/or chemical methods (Reife, 1993) however, methods enabling the recycle/reuse of dye-based color have been developed (Reife and Freeman, 1996). 

In the early 1950s, a number of cases of sickness occurred in children who had reportedly eaten candy and popcorn colored with excessive amounts of dye. As a result of these illnesses, new animal feeding studies were undertaken by the FDA. These studies were conducted at higher levels and for longer test periods than any experiments previously conducted and resulted in unfavorable findings for FD C Orange No. 1, FD C Orange No. 2, and FD C Red No. 32. 

Besides physicochemical methods, the use of microbiological growth-inhibition assays to test meat and milk for the presence of antibiotics residues is popular over a long period of time. These tests use antibiotic-sensitive bacterial reporter strains, such as Bacillus subtilis and Bacillus stearothermophilus var. calidolactis. These bacteria are inoculated under optimal conditions with and without sample. After culturing, results are read from visible inhibition zones or from the color change of the bacterial suspension in agar gels [6]. 

Data reporting (i.e., the statement of the results of the proximate analysis test methods) usually includes (in some countries but not in all countries) descriptions of the color of the ash and of the coke button. As an interesting comparison, the test for determining the carbon residue (Conradson), the coke-forming propensity of petroleum fractions and petroleum products (ASTM D-189 ASTM D-2416), advocates the use of more than one crucible. A porcelain crucible is used to contain the sample, and this is contained within two outer iron crucibles. This corresponds to the thermal decomposition of the sample in a limited supply of air (oxygen) and the measurement of the carbonaceous residue left at the termination of the test. 

Test the pH of each of the aqueous solutions. Do the test by first dipping a clean glass rod into the solutions and then transferring a drop of liquid to pH paper. Use a broad pH indicator paper (e.g., pH range 1-12) and read the value of the pH by comparing the color to the chart on the dispenser. Record the results on the Report Sheet (2). 

To each of the test tubes, add 5 drops of 10% NaOH solution and 2 drops of a dilute CuS04 solution while swirling. The development of a purplish-violet color is evidence of the presence of proteins. Record your results on the Report Sheet. 

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