Salinity is the measure and concentration of all the salts dissolved in water. Usually measured in parts per thousand (ppt or ), ocean salinity is 35ppt and the average river water salinity is 0. 5ppt or less (University of Rhode Island). Many factors go into salinity, making water salty. To name a few, salinity affects the environment through sediment from rocks washes into the ocean, evaporation of ocean water, and sea ice formation are known to increase the salinity of the ocean (NASA). It can also effect the environment if high concentrations run off to a nearby freshwater source.
Measuring salinity was very difficult in early times. During years 300 and 600, observations of changes in salinity, temperature, and smell helped civilizations such as Polynesians explore the southern portion of the Pacific Ocean. In the mid-1870s, scientists measured not only salinity and temperature, but also water density with the help of new techniques and technologies for measuring salinity, temperature, and water density in the world’s oceans. With a refractometer, salinity is measured through either the change of direction or bending of light when it transfers from air to water (University of Rhode Island).
The purpose of this lab is to identify the barrels that exceed five percent over the regulated amount and treat these compounds through techniques while maintaining the budget of $15,000. The first experiment called Briny Barrels, consisted of identifying the 5 “barrels” through two different techniques, which utilizes the salt content of the solutions (exceeds the limit percentage) and utilizing GC Mini to determine what the mixtures contain. The second experiment, Volatile Organics, tested the salinity in the barrels and which would exceed the limit percentage of salinity.
In this lab, the two methods used to determine salt content in the water solution is through refractometer usage and conductivity. To conclude, the unknown compound assigned ended up to be methanol while the standard compound given was acetone. The intended purpose of these two experiments not only displayed the salinity percentage of the barrels but also what the mixtures contained. This report will discuss the two different experiments that have been practiced through this period.
Methods: The goal of the “Briny Barrels” experiment was to identify 25 barrel solutions of sodium chloride, where five of these barrels are categorized as hazardous. This experiment called for determining the salinity through mass. To determine mass, a small, cleaned watch glass was labeled with the sample number on the bottom using a permanent marker. The watch glass was weighed in grams. 2 mLs of the sodium chloride solution was pipetted into a 10 mL graduated cylinder that would be transferred to the watch glass.
After this transfer, the watch glass and sample were reweighed and recorded. To figure out the mass of the solution, the plain watch glass was subtracted from the plain watch glass plus solution. The watch glass was placed in the oven for approximately 20 minutes until the water evaporated, and then it was cooled to room temperature. The watch glass was reweighed. The mass of the sample solution was greater than the salts alone, which indicated that the calculations were reasonable. In addition, the mass of the sample solution with the watch glass was more than the empty watch glass.
Using the obtained masses, the salinity for each sample was determined by using this equation: (weight of salt)/ (weight of sample)*1000=salinity (This would be labeled under parts per thousand. ) To use the refractometer, 1-2 drops of saline solution were placed on the stage of the refractometer to determine the salinity. After acquiring the refractometer, 1-2 drops of saline solution was placed on the refractometer’s stage. Afterward, the stage cover was closed. After a natural light source was located, looking outside the window worked, the efractometer was pointed towards the light source and the salinity measurement was read using the scale for salinity (o/oo) on the right side and then that value was recorded. After recording the measurements, the refractometer was then cleaned with the usage of distilled water. The refractometer’s stage was dried by gently blotting with a Kim wipe. The refractometer was cleaned by using and drying both the lens/ stage and the stage cover. For the remaining samples, these steps were repeated.
In the experiment “Volatile Organics,” the purpose was to become familiar with the use of gas chromatography through two techniques (evaporation, refractometer, etc. ) in determining the volatility of a chemical through five barrels that exceeded regulatory levels, while being aware of the organic compounds holding the waste mixtures through acetone, methanol, and 2-butanone. In order to for the salinity to be determined in the ‘Volatile Organics” experiment, the GC Mini was turned on and warmed up. During this time, a needle of the syringe was soaked in methanol solution which then was dried with a Kim wipe, to sterilize the syringe.
The inside of the syringe was cleaned when 1. OuL of methanol was drawn through the syringe and pressed where it would plunge down to release the methanol on a Kim wipe. This rinse was repeated three times before drawing the next sample. Once the GC Mini was warmed up, 0. 1ul of a sample was drawn into the syringe. Next, this sample was injected into the syringe into the GC Mini column while simultaneously pressed the plunger and the collection button on the Lab Quest Handhold device to trigger the process, where it was calculated in a charted series.
Afterward, the syringe was cleaned using the methanol technique stated previously. After time passed, and after the completed data was collected and retrieved, the graph was stored and the GC Mini had to warm up again for two times until there were 3 graphs of the same unknown. This procedure was repeated for all the samples until all the samples were tested. After this, the graphs were stored onto a flash drive where the data was transferred to Excel. With the known sample graphs given for each of the organic compound, methanol, acetone, and 2-butanone, the unknown compound mixtures were determined and labeled accordingly.
Discussion: As mentioned in the introduction, bring water and volatile organic compounds contribute to the search for proper chemical disposal. These chemicals are hazardous; therefore, it will cost money for a company to dispose of them. For the most part, the results were reasonable. Although there we many successes in these experiments, there were also sources of error. For the Briny Barrels experiment, Table 2b displays the data of the retested measurements of the salinity. Table 2a and Table 2b display the contrast between the original measurements and the retested measurements.
Due to the error discovered in barrels 16, 19, 20, 24, 31, 36, 39, 44, 46, 49, and 50, the salinity lab was retested to fix the errors (Table 2b). To fix these errors, the lab conducted an experiment (outside procedure) where it used a conductivity and salinity probe. Because of the inaccuracy of these measurements and the usage of these new instruments, these salinity measurements were retested and affected the budget, increasing the costs (Figure 1). During the briny barrels experiment, 16 barrels exceeded 5% per liter of water (50ppt) while measuring salinity by mass.
The barrels that exceeded 50ppt were 3, 10, 11, 13, 17, 18, 22, 24, 26, 30, 31, 39, 42, 45, 47, and 49 (Table 2b). This indicated that these barrels were above the regulated amount. During this same experiment, 26 barrels exceeded the 5% (50ppt) threshold. These were barrels 3, 4, 6, 8, 10, 11, 13, 17, 18, 20, 22, 24, 25, 26, 27, 30, 31, 34, 38, 39, 42, 44, 45, 47, 49, and 50 (Table 2a, Table 2b). These barrels were not only above the regulated amount, but they indicate that measuring using a refractomer would be better to use due to its accuracy in recognizing barrels that are above this threshold.
Salinity by mass resulted in a more exact manner; however, it is less efficient since it took longer. Contrasted to this, the retest used the most efficient and exact method. In the ‘Volatile Organics” experiment, methanol is interpreted as the “unknown waste. ” This is displayed through Figure 2, where the retention rate is 1. 275 minutes and its peak signal is 1. 4 mV. The range for methanol due to its similar voltage and retention time, when comparing Figure 2a and 2b. Because these chemical mixtures contain acetone, methanol, and 2-butanone, the simplest way to determine the volatility of these chemicals is through gas chromatography.
During this experiment, the standard solution was experiment through three trials. Trial #1 has a time of 1. 45 minutes for retention strength with a 1901. 9 mV signal strength. Trial #2 has a time of 1. 55 minutes with signal strength of 77. 2 mV. Trial #3 has a time of 1. 115 minutes with signal strength of 1813. 3 mV. The budget was capped at $15,000. Table 1 indicates that the project was under budget. Because of these, it would be more efficient to use these chemicals since it is lowcost to operate.
Conclusion: The purpose of this lab is to figure out the percentage of sodium chloride in each barrel of solution such that disposal cannot surpass five percent per liter (50 ppt), but also identify the volatile organic compounds found in these barrels. The standard organics were acetone, methanol, and 2-butanone. In the briny barrels lab, 16 salt barrels exceeded the 5% threshold (50ppt) were while measuring the salinity by mass (Table 2b). While measuring the salinity with the refractometer, 26 barrels exceeded the 5% threshold (Table 2a).
The error discovered in this experiment was the inaccuracy in 11 of the salinity levels. This composed of retests, which affected the budget by adding up costs (Table 1). Restesting would increase the cost up to about $1650, depending on both trials. The global and local impact of this lab exhibits the importance on wastewater and chemical disposal. These toxic substances require a certain way of disposal due to its composition of different salinity measurements as well as different toxicity in volatile organic compounds.
