Most differential stains have a challenge step that follows staining with a primary dye. In the Gram stain the challenge step is a rinse with either ethanol or acetone (either may be used). This step dehydrates and tightens the cell wall of Gram positives (mainly peptidoglycan) such that the rinse does not enter the cell. Gram negatives have mainly a lipid cell wall (even though they do contain peptidoglycan) that allows the challenge rinse to penetrate the cell and rinse out the crystal violet-iodine complex rendering the Gram negative cell colourless. Thus, the Gram negative cells must be stained to be seen, and this is done with the counter stain.
The dichloromethane is then separated from the mixture in the rotary evaporator. Figure 1: The structure of caffeine is very similar to those of purine bases (adenine and guanine) in DNA, therefore caffeine is a good substance to practice on for dealing with nucleic acids. Procedure Approximately 10g of tealeaves, CaCO3 (4.8g, 0.048 mol) and deionised H2O (100mL) is added into a beaker and boiled for 15 minutes. The mixture is then cooled to 20˚C and is filtrated using a Buchner funnel (vacuum filtration). The extraction process is when a solvent, dichloromethane (15mL) is added to the filtrate in a separatory funnel; the mixture is gently swirled together 3 times, and stopcock is released in between to vent the funnel.
The conical flask was then positioned to just under the burettes dropper which had its stopcock opened to allow a medium drip rate and had the sheet of filter paper slipped under it so that the colour could be seen more earily. As it was dripping the conical flask was gently stirred to allow the two substances to mix together. 10.
Tannins, which are organic compounds that can bind to alkaloids such as caffeine, are going to be taken out of the tea water using sodium carbonate. The sodium carbonate is a base, which will convert the acidic tannins into sodium salts that are highly soluble in water. Isolating the caffeine will continue once methylene chloride is added to the remaining tea solution, which increases the solubility of the caffeine. Methylene chloride can be evaporated quickly leaving the caffeine to be purified by sublimation. Materials and Methods: The tea solution was obtained when a tea bag was placed in boiling water and its liquid mix was carefully squeezed into a beaker; and eventually placed into a test tube.
Then by writing a balanced chemical equation and using the titration formula, Nb+Ma+Va=Na+MbVb , the molarity is able to be determined. Procedure: 1) Using the graduated cylinder add 10.0 mL of water into the Erlenmeyer flask. 2) Add 5.0 mL of HCl into the flask using another graduated cylinder because acid goes into water when mixing them. 3) Add three drops of phenolphthalein indicator into the flask. 4) Swirl the flask in circular movements to mix the substances.
Epoxy resins are generally cured with primary/secondary polyamines, anhydrides, and polyamides. A cross-linked structure is produced; this network structure is the desired infusible, insoluble product [2]. EXPERIMENTAL Materials: Piperazine, Toluene, Dow -D.E.R. 331- (Epoxy Resin), MDAP –diamine-, triethylamine Reflux Set-Up( 2-neck round bottom flask, vigroux column, thermometer, heater, boiling chips) Glass Rod,
Introduction Caffeine is a molecule that is similar to the purine base xanthine. The only recognizable difference is that caffeine has a methyl group. The goal of this experiment is to isolate caffeine from tea leaves, and then purify it by using sublimation. This experiment will use three techniques, extraction, recrystallization and melting point determination. A sequence of extractions has to be done to take out the other components from tea.
I. Experimental Objective(s): The objective of this experiment is to extract caffeine from tealeaves with boiling water. Once the caffeine is extracted it will then be isolated from most of the colored compounds by extraction with dichloromethane. After this the crude caffeine will be recrystallized, and then further purify it by sublimation. This will produce a white crystalline solid.
The sheet, which can be the size of a microscope slide, is placed on end in a covered jar containing a shallow layer of solvent. As the solvent rises by capillary action up through the adsorbent, differential partitioning occurs between the components of the mixture dissolved in the solvent the stationary adsorbent phase. The more strongly a given component of a mixture is adsorbed onto the stationary phase, the less time it will spend in the mobile phase and the more slowly it will migrate up the plate. The following are some common uses of Thin-Layer Chromatography: 1. To determine the number of components in a mixture.
Organic Chemistry Preparation of Methyl Orange Purpose In this experiment the azo dye methyl orange is prepared by the diazo coupling reation. Introduction The first step is called “diazotization”. The first product obtained from the coupling is the bright red acid for of methyl organge, called helianthin. In base, helianthin is converted to the orange sodium salt, called methyl organge (1). Reaction Scheme [pic] Although sulfanilic acid is insoluble in acid solutions, it is nevertheless necessary to carry out the diazotization reaction in an acid (HNO2) solution.