History[ edit ] Benzoic acid was discovered in the sixteenth century. In Salkowski discovered the antifungal abilities of benzoic acid, which was used for a long time in the preservation of benzoate-containing cloudberry fruits.
A nutrient used by plankton in ocean nourishment experiments for geoengineering purposes As an additive to extend the working temperature and open time of hide glue As a solubility-enhancing and moisture-retaining additive to dye baths for textile dyeing or printing As an optical parametric oscillator in nonlinear optics   Adverse effects[ edit ] Urea can be irritating to skin, eyes, and the respiratory tract.
Repeated or prolonged contact with urea in fertilizer form on the skin may cause dermatitis. Ingestion of low concentrations of urea, such as are found in typical human urineare not dangerous with additional water ingestion within a reasonable time-frame.
Urea can cause algal blooms to produce toxins, and its presence in the runoff from fertilized land may play a role in the increase of toxic blooms. The first step in the conversion of amino acids from protein into metabolic waste in the liver is removal of the alpha-amino nitrogen, which results in ammonia.
Because ammonia is toxic, it is excreted immediately by fish, converted into uric acid by birds, and converted into urea by mammals.
Ammonia is smaller, more volatile and more mobile than urea. If allowed to accumulate, ammonia would raise the pH in cells to toxic levels.
Therefore, many organisms convert ammonia to urea, even though this synthesis has a net energy cost. Being practically neutral and highly soluble in water, urea is a safe vehicle for the body to transport and excrete excess nitrogen. Urea is synthesized in the body of many organisms as part of the urea cycleeither from the oxidation of amino acids or from ammonia.
In this cycle, amino groups donated by ammonia and L- aspartate are converted to urea, while L- ornithinecitrullineL- argininosuccinateand L- arginine act as intermediates. Urea production occurs in the liver and is regulated by N-acetylglutamate. Urea is then dissolved into the blood in the reference range of 2.
In addition, a small amount of urea is excreted along with sodium chloride and water in sweat. In water, the amine groups undergo slow displacement by water molecules, producing ammonia, ammonium ionand bicarbonate ion.
For this reason, old, stale urine has a stronger odor than fresh urine. The cycling of and excretion of urea by the kidneys is a vital part of mammalian metabolism. Besides its role as carrier of waste nitrogen, urea also plays a role in the countercurrent exchange system of the nephronsthat allows for re-absorption of water and critical ions from the excreted urine.
Urea is reabsorbed in the inner medullary collecting ducts of the nephrons,  thus raising the osmolarity in the medullary interstitium surrounding the thin descending limb of the loop of Henlewhich makes the water reabsorb. By action of the urea transporter 2some of this reabsorbed urea eventually flows back into the thin descending limb of the tubule,  through the collecting ducts, and into the excreted urine.
The body uses this mechanism, which is controlled by the antidiuretic hormoneto create hyperosmotic urine—i. This mechanism is important to prevent the loss of water, maintain blood pressureand maintain a suitable concentration of sodium ions in the blood plasma.
The equivalent nitrogen content in gram of urea in mmol can be estimated by the conversion factor 0. Other species[ edit ] In aquatic organisms the most common form of nitrogen waste is ammonia, whereas land-dwelling organisms convert the toxic ammonia to either urea or uric acid.
Urea is found in the urine of mammals and amphibiansas well as some fish. Birds and saurian reptiles have a different form of nitrogen metabolism that requires less water, and leads to nitrogen excretion in the form of uric acid. It is noteworthy that tadpoles excrete ammonia but shift to urea production during metamorphosis.Nov 25, · Crystals are beautiful, both externally at the macroscopic level and internally at the atomic level.
The same is true for the process of crystallization, whi. EXPERIMENT #1 –Recrystallization Post-lab Assignment - Spring This post-lab assignment is available from January 31 until February Post-lab Question #1. Julie a CHEM student was given a sample of pure Compound Post-lab Question #2.
A CHEM . EXPERIMENT 2: Recrystallization and Melting Point Recrystallization (or Crystallization) Your complete report for this experiment should include the data page, answers to the following questions, and a conclusion (1 page maximum. EXPERIMENT 2: Recrystallization and Melting Point.
Chem Experiment 2 Recrystallization and Melting Point Determination of Benzoic Acid Essay RECRYSTALLIZATION AND MELTING POINT DETERMINATION OF BENZOIC ACID ANSWERS TO QUESTIONS 1.
How does the use of fluted filter paper hasten filtration? In this experiment, you will prepare the Grignard reagent (or use previously prepared chemical), phenylmagnesium bromide. Phenylmagnesium bromide will be used to produce either benzoic acid (reaction with CO 2 ; dry ice) or triphenylmethanol when reacted with benzophenone (or ethyl benzoate).
Organic Chemistry Experiment #3 Recrystallization 1 It is possible to purify compounds by recrystallizing them in a solvent in which they are soluble at a .