Chromatography Lab Report Example | Topics and Well Written Essays - 1500 words

Chromatography - Lab Report Example Unknown mixtures of dyes were also resolved into their respective components using paper chromatography. Chromatography is a separation technique that determines the components of a mixture. Drug tests of blood and urine samples as well as determining the presence of harmful substances in drinking and groundwater are the most common uses of chromatography. The solid or liquid stationary phase holds the mixture to be separated. In addition, it is the medium to which the mobile phase passes through. On the other hand, the liquid or gaseous mobile phase passes along the stationary phase and in the process carries the components of the mixture with it. In the end of the experiment, separate bands are observed, representing the different components that move along the stationary phase at different rates. The chromatogram is the pattern of separated bands produced after chromatography. Each band is characterized by its retention factor, which is the ratio of the distance between the origin line and the band of the component and the distance between the origin line and the solvent front. In paper chromatography, a specialized paper made of cellulose is used as the stationary phase. The best mobile phase for a particular separation experiment depends on which solvent system the sample components have different Rf values. Thus, measurement of Rf values of the individual sample components in a variety of solvents is necessary in deciding which solvent to use as the mobile phase. This experiment was conducted to determine, through paper chromatography, the retention factors (Rf) of the seven pure food dyes, red 3 (R3), red 40 (R40), blue 1 (B1), blue 2 (B2), yellow 5 (Y5), yellow 6 (Y6), and green 3 (G3), approved by the Food and Drug Administration (FDA) and dissolved in three different solvent systems, distilled water, 70% isopropyl alcohol, and 0.10% sodium chloride (NaCl)

Ancient Roman Architecture Essay Example | Topics and Well Written Essays - 1750 words

Ancient Roman Architecture - Essay Example The Etruscans inspired the pedestal or podium below the early Temple of Jupiter Capitolinus in 509 B.C. The true arch may or may nit have come to Rome from Etruria, but both peoples often used the corbel arch and both liked decorative terra cotta. The Punic wars I and II, during the third century B.C., brought Rome into contact with Greek culture of southern Italy and Sicily; and with the conquest of Corinth, in 146 B.C., Rome subjugated Greece itself. From the Hellenistic and later Greeks, the Romans adopted the orders of architecture but modified them. They added a base to the Doric column and lightened its proportions to eight lower diameters in height. They joined the volutes of the Ionic capital with straight lines instead of the delicate Greek curves. The Corinthians was their favorite order. To the three Greek orders they added the Tuscan, a simplified version of the Structurally, the most important innovation of the Roman was the arch, which they used widely although they had not invented it. Next to the post and lintel, arch construction is historically of greatest importance. An arch is made of wedge-shaped stones that are arranged with the small side of the wedge turned down toward the opening. When the stones have been put in place by means of scaffolding or centering, their shape keeps them from falling, just like in the aqueduct of Segovia. Each stone of the arch, by its weight, exerts constant pressure on the stones an each side of it and the arch is held in position only by an exact balancing of these pressures. If that balance is upset, the arch collapses. As an old Arabic proverb has it â€Å"An arch never sleeps (The World Book Encyclopedia, p.640).†