CE 256 Lab 2 Report

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New Mexico State University *

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256L

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Civil Engineering

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Apr 3, 2024

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docx

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Electroconductivity Lab #2 CE 256L M02 Lab Date: 09/21/22 Report Due: 09/28/22 Group Members: Louis Mauriot, Cristian Sanchez, Omar Saucedo, Cristina Esquivel, Brittany Hymer

Table of Contents INTRODUCTION ........................................................................................................................................... 3 PROCEDURE ................................................................................................................................................. 3 RESULTS ....................................................................................................................................................... 4 DISCUSSION ................................................................................................................................................. 5 REFERENCES ................................................................................................................................................ 5 APPENDIX .................................................................................................................................................... 5 List of Tables Table 1 Group Results Table 2 Group Results Table 3 Other Groups Results List of Figures Figure 1: Langelier Equation Figure 2: Russel Equation Figure 3: TDS Resultant Equation

INTRODUCTION There is an alternative to last week’s methods of determining the amount of Total Dissolved Solids (TDS, which refers to the total quantity of solids remaining in a solution once filtration and evaporation have been completed) in a solution. This method is a lot more efficient especially on a time scale. Last week, the final lab results were obtained 24 hours after performing the original experiments. Each sample contained within a crucible, or an aluminum dish were stored in a drying oven to estimate the amounts of TSS and TDS for each. This alternate method studied here in this lab allows us to acquire instantaneous results. Using the variation of the number and types of ions present in the solution being tested, we can therefore use electrical conductivity (EC) to help determine the quantity of TDS present in the solution. EC is by definition the ability of a solution to carry an electrical current. Other than the quantity of ions being a varying factor for resultant data, we need to also consider factors such as the temperature of measurement and the mobility valence. It is important to note that bases, salts and solutions of most inorganic acids are on average good conductors. Poor conductors consist of non-dissociative organic compounds. As seen in the previous lab, the amount of TDS contained in a solution sample is highly indicative of the actual potability of water. As mentioned previously, the TDS tests seen last week require a lot of time to perform properly. This EC test we are about to experiment only indicates the TDS level in a sample but is very helpful for many different types of water. In the professional world, the EC test is used quite often. In a laboratory setting, the quality of the DI water used can be measured thanks to the EC test. Out in the field, it also serves a purpose when it comes to measuring changes in surface and groundwater quality caused by a source of groundwater contamination or a wastewater discharge among other causes. The units used for an EC test in a laboratory setting are commonly µmhos/cm (mho = 1/ohm). PROCEDURE This lab consists of a single procedure repeated at different locations around campus. Initially, the lab instructor provides us with a conductivity meter, a bottle of DI water and a plastic drinking cup in the laboratory room. Each laboratory group (which consists of an average of 3-4 people) is then assigned an area on campus. The objective, if we chose to accept it, was to collect at least 3 EC measurements from 3 separate samples in 3 specific locations of the assigned area. In order to fulfill the objective by trying to prevent any kind of human or systematic errors, the usage of the conductivity meter needed to follow very specific steps. At first, the probe part of the conductivity meter or conductivity cell is disinfected. We rinse it with the DI bottle of water. The water sample is then collected from the nearest source of water (which can vary from a water fountain to a pond depending on the location). Once

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