Abstract
The purpose of this experiment was to use spectroscopy in order to measure the maximum wavelength of “fast green” dye. The maximum wavelength was found to be 620 nm. The absorbance over time was also measured for the reaction of .0001 M “fast green” dye and 1mL of 6% NaOCl, commonly known as bleach. This reaction took 16 minutes to fully react to a point where it was immeasurable by the spectrophotometer. In the lab, a spectrophotometer was used in order to determine the intensity of light emitted through the dye samples. With the Beer-Lambert law the relationship between known concentrations and absorbance helped calculate the concentration of the dyes.


Introduction
Spectroscopy deals with light and how light interacts with matter. Light has both wave and particle properties. The energy of a wave directly relates to the wavelength of the light. The longer the wavelength the lower the energy. The shorter the wavelength the higher the energy it is. These wavelengths correspond to colors in between specific wavelengths. The spectrum is the visible light spectrum and is what is colloquially known as the rainbow. The highest energy and therefore lowest wavelength is violet, while the lowest energy and therefore longest wavelength is red. The other wavelengths are not visible to the naked eye. In this lab the the intensity of the light was determined before and after light met the sample of dye which is called the transmittance. The transmittance is defined as a value between 1 and 0 with low having little light passing through and high values passing through a lot of light. 1The absorbance of light is the negative natural log of transmittance. If absorbance is a low number little is absorbed while if its high a lot is absorbed. 2The Beer-Lambert Law is A=ε*l*cwhere A stands for absorbance, the greek letter epsilon, ε, stands for a constant that is named the extinction coefficient. the l stands for length and c stands for concentration.
Ten-fold dilutions are crucial to this experiment. A ten-fold dilution is used to lower the
 concentration of a liquid in water. To do this a sample for example starts off at .01 M. The desired concentration is .0004 M. 4 mL of the sample is placed in 6 mL of water. This makes a new .004 M solution. 1 mL of this is placed in 9 mL of water. This makes the desired .0004 mL of the sample. It is called a ten-fold dilution because the concentration of the sample is changing by 10-1 each time.


Procedure

		The experiment started by setting up the equipment and using proper safety measures. Goggles were placed on eyes, and lab coats were worn to protect from the bleach and dye. The dye that was used was green 3, “fast green” dye. The dye was concentrated (.01 M) so spills were avoided in order to have no stains anywhere. A spectrophotometer was also set up. This spectrophotometer was used with care for it is a very expensive device.
		The first step was to perform ten-fold dilutions in order to get the dye to the desired concentration. The desired concentrations were .001 M, .0001 M, .00001 M, .00008 M, .00005 M, .00003 M. Normal tenfold dilutions were used for the dilutions ending in 1, for the other dilutions for example the .00003 M concentration, the dilution was performed as such: 3 mL of .01M  dye was placed in 7 mL of water getting .003M dye. Then 1mL of that was placed in 9 mL of water receiving .0003 M dye. This last step was repeated once more in order to get the desired .00003 M dye. Once the concentrations were gotten the experimental part of the lab began.
		The first part of the experiment was to find the maximum wavelength of the green dye. to do this using a 1 cm cuvette, and starting at a wavelength of 400 nm, the cuvette was filled with deionized water. This was placed inside of the spectrophotometer and then subsequently the absorbance was zeroed. Next, the .00001 M dye was placed in the spectrophotometer, and the absorbance was observed and then recorded. Wavelength was changed in increments of 20 nm until 700 nm was reached. The data observed during this part of the experiment is available in table 3.
The second part of the experiment was to observe the absorbance values for the “fast green” dye at different concentrations. The different concentrations were placed in the cuvette and the absorbance was observed using the spectrophotometer. The data was recorded and is shown in table 1.
	The third and final part of the experiment was observing absorbance over time. This was done by taking 1 mL of .0001 M green dye and putting it together with 1 mL of 6% NaOCl (bleach). The absorbance of the sample was noted every ten seconds until 5 minutes up until 20 minutes. A timer was used on a phone with the “lap button.” This was in order to see how far away from the ten seconds each measurement was taken. The average time for the ten second interval ranged from 9.90 seconds to 10.10 seconds with some outliers. This means that there is error in the data from human reaction time. The data was recorded and is in table 3.
	Following the experiment proper lab safety was taken and the dyes and bleach placed in the correct container. Gloves were thrown out in solid waste along with the glass containers. The stations were cleaned up and wiped down with water and paper towels.
  Data and calculations

Table 1:
Concentrations
Absorbance
.00003 M
1.699
.00001 M
.567
.000005 M
.299
.000001 M
.078





This is the data found for the different concentrations of “fast green dye”
Equation used was the Beer-Lambert law: A=ε*l*c with l being a cuvette of size 1 cm
.00003 M
1.699 = ε * 1cm * .00003M
ε = 56633.3
.00001 M
.567  = ε * 1cm * .00001M
ε = 56700
.000005 M
.299 = ε * 1cm * .000005M
ε = 59800
.000001 M
.078 = ε * 1cm * .000001M
ε = 78000






The graph shows the calibration curve of “fast green” dye. The calibration curve plots the concentration of the dye against the absorbance at that concentration.




This graph shows the absorbance of the dye at time T in seconds. This shows how the dye reacts over time.
		Table 2:
    Time
 Absorbance
Time
Absorbance
Time
Absorbance
Time
Absorbance
0:10
1.150
2:30
0.360
4:50
0.194
11:30
0.032
0:20
1.008
2:40
0.343
5:00
0.184
12:00
0.029
0:30
0.899
2:50
0.327
5:30
0.175
12:30
0.027
0:40
0.799
3:00
0.311
6:00
0.150
13:00
0.025
0:50
0.723
3:10
0.296
6:30
0.129
13:30
0.024
1:00
0.653
3:20
0.283
7:00
0.111
14:00
0.023
1:10
0.600
3:30
0.270
7:30
0.095
14:30
0.022
1:20
0.552
3:40
0.257
8:00
0.082
15:00
0.021
1:30
0.515
3:50
0.246
8:30
0.070
15:30
0.020
1:40
0.480
4:00
0.235
9:00
0.600
16:00
0.020
1:50
0.450
4:10
0.223
9:30
0.520
16:30
0.020
2:00
0.425
4:20
0.213
10:00
0.046




2:10
0.401
4:30
0.203
10:30
0.040




2:20
0.379
4:40
0.194
11:00
0.036




This graph shows the absorbance of the dye against the wavelength of the dye. This graph shows that the highest wavelength value is at a 620 nm wavelength with an absorbance of .561.







Table 3:
 Wavelength (nm)
Absorbance
400
0.038
420
0.052
440
0.043
460
0.02`6


480
0.024
500
0.034
520
0.048
540
0.071
560
0.122
580
0.209
600
0.363
620
0.561
640
0.330
660
0.057
680
0.003
700
0.000


Conclusion
Overall this experiment was very successful. The hypothesis - that one can determine a calibration curve, the extinction coefficient, and also the maximum wavelength of the dye was proven to be true. The maximum wavelength of the “fast green” dye was found to be 620 nm. The experiment in which absorbance over time was determined that it took 16 minutes for the reaction of 1 mL bleach and .0001 M to fully take place. One reason why this lab was successful was because using a spectrophotometer there is little room for error. Possible errors come from mis-performed dilutions and miscalculations. One error that was experienced with the spectrophotometer was the spectrophotometer only can read absorption values up to a certain point. After that the numbers blink which means it did not take a successful reading. This was remedied by using a lower dilution of the sample so it did not affect the data. Other errors stem from human error of reaction time when timing when to write down absorption. A potential way to solve this would be to have a camera take a picture with a timer that goes off every ten seconds. This way it would be a timer run by the computer and have little error in comparison to a human.