Test tube holder, making

STRIP OF THIN CARDBOARD MAKES AN ADEQUATE TEST TUBE HOLDER. IF YOU LIKE, YOU CAN MAKE A HOLDER FROM CLOTHES HANGER WIRE AS SHOWN HERE. 

Place the test tube in a test tube holder. Immerse the test tube in the sand bath. Make sure the test tube points away from your face. (Caution Do not touch either the test tube or the beaker with your hand.) Heat the mixture in the test tube to about 140°C. The mixture will turn yellow. 

An absorbance measurement of a sample is obtained as follows. Rinse a clean cuvette or the indexed sample test tube with distilled water and then with several milliliters of sample solution. Half fill the cuvette or the test tube with sample solution, and make certain that the solution is free of bubbles and that the exterior surface of the cuvette or the test tube is wiped clean with a tissue. Then insert the cuvette or the test tube carefully into the sample holder, and close the door. Read the absorbance of that solution directly from the meter. Then remove the cuvette or the test tube from the sample holder, and rinse the cuvette or the test tube with distilled water so that it is ready to receive the next sample. Repeat the above procedure until all absorbance readings at a given wavelength have been obtained. 

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