red dye number 40

Topics: Light, Laboratory glassware, Pipette Pages: 4 (1196 words) Published: April 15, 2014
 Determining the concentration of red dye #40 in an unknown solution

Introduction: White light is composed of many different wavelengths of light combined together. A spectrophotometer is an instrument that shines a single wavelength of light of a known intensity into a solution and then measures the intensity of the light exiting the solution. If a solution contains any compound that absorbs light, the intensity of light exiting the solution will be less than what entered the solution. On the other hand, if none of the compounds in the solution absorb at that wavelength of light, then the intensity of the light exiting the solution will be the same as that entering. The intensity of light that passes through an absorbing solution is dependent on the concentration of the absorbing compound in solution. In other words the more material in the solution absorbs the light, the less light will get through. This relationship is expressed by Beer’s Law Procedure: Work with partners.

You and your partner will be assigned a unknown solution containing red dye #40. Your standard curve is to be prepared for this particular color of dye.

Step one
(1)Turn on the spectrophotometer before preparing the solutions since it requires about 15 minutes to warm up.
1.Make sure the volumetric flasks are clean. If they appear dirty, wash them with soap and water, and do a final rinse with DI water. Dry the outside completely. The inside may remain wet since DI water will be added to the flask. Label three of the volumetric flasks #2-4.

2. Obtain about 50 mL of the stock solution in a 100 mL beaker. Transfer about half of the solution to a large test tube labeled #1. Use only about 10 mL of solution to condition a 25.00 mL volumetric pipet, then use the pipet to transfer 25.00 mL of the stock solution to the clean volumetric flask...
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