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Trial Number 11

Trial Purpose:

To determine a method for bath life monitoring.

Date Run:

12/03/1998

Experiment Procedure:

A 125mL sample of the Soy Gold product was diluted to 50% by volume using DI water at room temperature. From this stock solution several contaminated solutions were made up using the dirty D-Greeze 500 cleaning solution. Each solution was made in a 15 mL test tube. Using LaMotteā€™s Smart Colorimeter at 420 nm, percent transmittance and absorbance readings were recorded for a blank solution (Soy Gold 50%) and seven solutions. The values were plotted to determine the correlation between contaminant loading and colorimeter readings. Two trials were conducted for %Transmittance and absorbance.
The concentrations used were:

Contaminant     Volume   Stock Volume
      % (mL) (mL)
0 0 15
2.5 0.375 14.625
5 0.75 14.25
7.5 1.125 13.875
10 1.5 13.5
12.5 1.875 13.125
15 2.25 12.75
20 3 12

SUBSTRATE MATERIAL: Liquid-AG Environmental Soy Gold 2000 @ 50%
CONTAMINANTS: Dirty cleaning solution, Solvent Kleen D-Greeze 500 w/ residual paint chips and pumice sludge
CONTAMINATING PROCESS USED: Added known volume to Cleaning Solution
ANALYTICAL METHODS: Colorimeter-%Transmittance and Absorbance at 420 nm

Trial Results:

Both %Transmittance and Absorbance were found to have adequate relationships with the amount of contaminant added to the stock solution.  These relationships were determined to be exponential in nature.  Using spread sheet calculations, the %Transmittance values were found to be a better match than the absorbance data.  Table 1 lists the information gathered in Trials 1 and 2.

Table 1.  Resultant Data for Trials 1 & 2

Contaminant   Trial 1   Trial 2
Vol % % Trans Absorbance % Trans Absorbance
0 102 0.01 98 0.01
2.5 84 0.08 82 0.09
5 55 0.26 61 0.27
7.5 59 0.23 57 0.24
10 51 0.29 51 0.29
12.5 45 0.35 45 0.35
15 43 0.37 41 0.39
20 37 0.43 37 0.43

Correlations: 0.953 1.16 0.952 1.16

The Figures 1 & 2 show the %Transmittance relationship to contaminant concentrations.
Figures 3&4 illustrate the absorbance data graphically. These graphs reveal that the values obtained for the 5% may be the reason for the discrepancies in the correlation factors.

Success Rating:

A cleanliness study, addressing only various analytical techniques.

Conclusion:

Using a colorimeter, the %Transmittance at 430 nm was determined to be a possible method for monitoring bath life.  The next step will be to correlate the %Transmittance readings to cleaning efficiency.

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