2.4.1 Peroxide based Bleaching Agents
These products usually contains hydrogen peroxide or one of its precursors as an oxidizing agent
a. Hydrogen peroxide (HP,H2O2) is an effective bleaching agent. It is a pale blue liquid and is slightly more viscous than water. The molar mass of hydrogen peroxide is 34.0147g/mol .As the molecular weight of hydrogen peroxide is low it can penetrate dentin and break the bond of organic and inorganic compound inside the dentinal tubules[36] .The photolysis of hydrogen peroxide can only be achieved by low frequency light of wavelength 365nm or less and heat[37, 38].
b. Sodium perborate (NaBO3) is odorless, white, water soluble powder. It is safest and most easily controlled material for bleaching when prepared with distilled water or hydrogen peroxide. It is stable in dry state but it breaks down to form sodium metaborate, nascent oxygen and hydrogen peroxide in presence of water, acid and warm air[2].Sodium perborate may be monohydrate ,trihydrate and tetrahydrate and are mostly used for intracoronal bleaching[39].
c. Carbamide peroxide (CH6N2O3 or CH4N2O•H2O2, CP), is a white crystalline solid which dissociates into hydrogen peroxide and urea upon contact with water .It is also called urea peroxide. Urea again dissociates into ammonia and carbon dioxide. The release of ammonia and carbon dioxide elevates the pH value of the bleaching agent in the oral cavity during the bleaching process. For bleaching purpose 10-35% of carbamide peroxide is used. Usually 10% carbamide peroxide produces 3-3.35% hydrogen peroxide.
2.4.2 Non Peroxide based Bleaching Agents
These materials are based on sodium chlorite (NaClO2) which are activated by citric acid. Sodium chlorite is an very good oxidizing agent wh...
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...mperature stable and visible light active oxygen rich anatase phase titanium dioxide[77].In this method hydrogen peroxide was added to amorphous titanium dioxide to form peroxo titania complex. The band gap of the resulting titania decreased as the molar ratio of the hydrogen peroxide was increased (figure 5). The band gap narrowing was identified as factor responsible for the visible light activity. The hydrogen peroxide modified samples were more photoactive and thermally stable.
Arti bandgar et.al. in 2012 used aqueous peroxo titanate complex (PTC) precursor to obtain pure titanium dioxide[81] .Several characterization were done such as DSC–TGA, XRD, UV–Vis, SEM and TEM. In the study reflux time of PTC has increase and crystalline size too. The surface morphology of TiO2 changed to rice like shape and furtherin ellipsoid rods like shape from hexagonal shape.
The purpose of the Unknown White Compound Lab was to identify the unknown compound by performing several experiments. Conducting a solubility test, flame test, pH paper test, ion test, pH probe test, conductivity probe test, and synthesizing the compound will accurately identified the unknown compound. In order to narrow down the possible compounds, the solubility test was used to determine that the compound was soluble in water. Next, the flame test was used to compare the unknown compound to other known compounds such as potassium chloride, sodium chloride, and calcium carbonate. The flame test concluded that the cation in the unknown compound was potassium. Following, pH paper was used to determine the compound to be neutral and slightly
Triphenylmethyl Bromide. A 400 mL beaker was filled with hot water from the tap. Acetic acid (4 mL) and solid triphenylmethanol (0.199 g, 0.764 mmol) were added to a reaction tube, with 33% hydrobromic acid solution (0.6 mL) being added dropwise via syringe. The compound in the tube then took on a light yellow color. The tube was then placed in the beaker and heated for 5 minutes. After the allotted time, the tube was removed from the hot water bath and allowed to cool to room temperature. In the meantime, an ice bath was made utilizing the 600 mL plastic beaker, which the tube was then placed in for 10 minutes. The compound was then vacuum filtered with the crystals rinsed with water and a small amount of hexane. The crude product was then weighed and recrystallized with hexane to form fine white crystals, which was triphenylmethyl bromide (0.105 g, 0.325 mmol, 42.5%). A Beilstein test was conducted, and the crystals produced a green to greenish-blue flame.
Three flat-bottomed vials were obtained and labeled one through three. 3 mL of hydrogen peroxide was distributed to each of the vials. One drop of liquid soap was then added to each of the vials. The contents of the vials were gently swirled to ensure mixture of the hydrogen peroxide and soap. In each vial, a pH buffer was added; vial one received pH 2 buffer, vial two received pH 7 buffer, and vial three received pH 12 buffer. 1mL of catalase was then placed into each vial and the reaction was timed for 2 minutes. At the end of two minutes, the bubble column produced was measured and recorded into Table 3. The results were then graphed, as shown in Figure
Because of its undeniable and scientifically-proven powerful antioxidant properties, catalase enzyme has a wide commercial application. Primarily in combination with the enzyme glucose oxidase, catalase is used as a preserving system in mayonnaise and egg products such as whole eggs or dried egg white, in the preparation of milk and cheese, in the manufacture of baked goods, beverages, textile industry, cosmetic industry (as face mask), and in cleaning agents for contact lenses, for the elimination of the hydrogen peroxide that is present in some products, (Worthington Biochemical Corporation,
This enzyme speeds up the break down of hydrogen peroxide into water and oxygen, as enzymes are biological catalysts. [IMAGE]The reaction: Hydrogen peroxide Water + Oxygen Catalase -------- [IMAGE] 2H2O2 2H2O + O2 Apparatus: Hydrogen Peroxide, Several sticks of celery, Stand, boss and clamp, 100ml conical flask, 25cm3 burette, 1800cm3 beaker, Rubber bung with delivery tube, Distilled water, Large container filled with water, 10cm3 measuring cylinder, 10cm3 syringe, 20cm3 syringe, Blender, Knife, Ceramic tile, Electronic balance (correct to 2 decimal places), Sieve, Stopwatch/timer. The variables: There are many possible variables in this investigation, such as pH, temperature, the concentration of substrate and the concentration of the enzyme.
2.2.1. The analysis for the ability of the antioxidant activity to prevent the occurred of hydroperoxide.
2H2O(aq) à 2H2O(l) + O2 (g) It is able to speed up the decomposition of hydrogen peroxide because the shape of its active site matches the shape of the hydrogen peroxide molecule. This type of reaction were a molecule is broken down into smaller pieces is called an anabolic reaction. I will be studying the effect of concentration of the catalase in this reaction. Hypothesis Hydrogen peroxide will breakdown to oxygen in water in the presence of catalase.
The aim of this paper is to take an in-depth look at the emotion of disgust, and explore what role (if any) it should play in morality. The issue of what role disgust should have in morality is disputed by advocates and skeptics. In what follows, I will outline this dispute and show the arguments each side makes. Following that, I will take a look into Kelly’s view which takes the skeptical stance, but differs in how he comes to take that stance. Next I will show how Kelly uses his view to disprove the disgust advocates’ arguments. Finally, I will illustrate a promising line of argument that may give hope to the disgust advocates, in light of Kelly’s powerful skeptical stance.
Racism is a intricate, multidimensional construct that can be private and public, as well as institutional and personal. In other words, racism does not only consist of blatant racial insolence; subtle systemic racism is also alive and well. However, Americans are fixed on the notion that bigotry hasn’t been an issue since the 20th century mass lynchings. The United States’ distorted view of racism maintains the idea the country’s racial issues are behind us. In his article, “Between Colorblind and Colorconscious: Contemporary Hollywood Films and Struggles Over Racial Representation,” Jason Smith demonstrates the ways in which color blindness ineffectively addresses racial injustices within society. Although the logic behind this theory works towards a noble goal, color blind theory proposes that
Hydrogen peroxide (H2O2), according to Bryce Fredrickson (1999-2014), has many useful properties due to its extra oxygen atom. Hydrogen peroxide consists of two hydrogen atoms and two oxygen atoms, whereas water (H2O) consists of two hydrogen atoms and only one oxygen atom (Balcony Garden Web, 2016). Hydrogen peroxide has many uses including cleaning, bleaching, and a few health benefits (Fredrickson, 1999-2014), however the main focus of this research project is on plant growth.
In this experiment the enzyme peroxidase and the substrate hydrogen peroxide were not mixed initially, instead they were both placed in separate tubes and were incubated at a specific temperature, to prevent hydrogen peroxide from undergoing any reaction with peroxidase until they both acquire the required temperature.
Colorism has became a huge issue in today’s society. Colorism is an issue because, it is a form of racism, it reflects back on the days of slavery, it is overall rude, and jail terms are affected.
Hydrogen peroxide is a liquid which contains hydrogen atoms as well as two oxygen atoms. The oxygen atoms are very strong oxidizing agents therefore in order to break this substrate down it must undergo oxidation. This can be done
The Concentration of Hydrogen Peroxide and Speed of The Rate at Which It is Broken Down by Catalase
Investigating the Effect of the Enzyme Catalyse On Hydrogen Peroxide Introduction The aim of this experiment is to determine the effects of varying enzyme (catalyse) on Hydrogen Peroxide. Hydrogen Peroxide + Catalyse à Water + Oxygen 2H2O2 à H2O + O2 + Heat Apparatus & Diagram [IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE] Bung Potato Hydrogen Peroxide Water Collected Oxygen Delivery Tube Measuring Cylinder [IMAGE] Using the Equipment Safely It is important that we use the apparatus carefully, as safety will be an issue throughout the whole experiment. We will wear goggles and an apron or lab coat to protect our eyes and clothes. As we are using enzymes and Hydrogen Peroxide we need to be extra careful, ensuring they don't come into contact with our eyes, skin or clothes. Catalyse is an enzyme found in all living cells.