Module:5 Lecture:30Chloroform Dr. N. K. Patel Module: 5 Lecture: 30 CHLOROFOrm INTRODUCTION Chloroform is an organic compound with formula CHCl 3. It is a colourless, sweet-smelling dense liquid and it is a trihalomethane which is considered somewhat hazardous. It is one of the four chloromethanes. Chloroform readily volatilizes from soil and surface water, which then produced phosgene, dichloromethane, formyl chloride, carbon monoxide, carbon dioxide and hydrogen chloride as undergoes degradation in air. Chloroform was discovered by three researchers independently of one another. The French chemist EugèneSoubeiran was reported chloroform in 1831. It was prepared from acetone (2-propanone) as well as ethanol through the action of chlorine bleach powder (calcium hypochlorite). Chloroform was named and characterized in 1834 by Jean-Baptiste Dumas. Several million tons are produced annually as a precursor to PTFE and refrigerants, but its use for refrigerants is being phased out. Chloroform has a multitude of natural sources, both abiotic and biogenic. Greater than 90% of atmospheric chloroform is of natural origin. The American physician Samuel Guthrie prepared gallons of the material and described its "deliciousness of flavor." Independently, Justus von Liebig also described the same compound. All early preparations used variations of the haloform reaction. MANUFACTURE 1. From acetone and bleaching powder Raw material Basis: 1000kg chloroform from acetone and bleaching powder (88% yield) Chlorine 1602kg NPTEL 1 Module:5 Lecture:30Chloroform Dr. N. K. Patel Methane (STP) 200kg Reaction Manufacture process Acetone Bleaching powder Cooler Water Chlrorform Water Water Sulfuric acid Reactor and Still Lime Still Acidifier Waste Spent acid Waste Figure: Manufacture of Chloroform from acetone and bleaching powder Block diagram of manufacturing process Diagram with process equipment Animation The bleaching powder containing about 34% available chlorine was slowly added in the ratio of about 0.161kg per kg of water to the cast-iron still, fitted with efficient agitation, cooling coils and heating coils. The suspension of bleaching powder in water was properly agitated. NPTEL 2 Module:5 Lecture:30Chloroform Dr. N. K. Patel Acetone (0.045kg of acetone per 0.45kg of bleaching powder) was slowly charged into the still and mixed with bleaching powder, where the temperature was maintained below 430C with the help of cooling coils and rate of addition. The pot temperature was increased upto 560C, after all the acetone has been added. Then gradually increasing the temperature to 650C where all the chloroform formed was distilled out from the still. The chloroform vapour were passed through a cooler and collected in a tank fitted with an agitator. The crude material containing chloroform and water mixturewas purified by agitation with concentrated sulfuric acid in a weight ratio of about 0.9kg of crude chloroform (distillate) per 0.45kg of sulfuric acid. After 2 - 3hr agitation, the crude chloroform was decanted from the acid and charged to a still, where it was distilled over lime (calcium oxide). The purified chloroform having purity of 99% and was obtained in 86 - 91% yield based on the acetone charged. Continuos process These processes may be run on a continuous basis and may use the mixture of acetone and acetaldehyde as the raw material. Industrial ethyl alcohol has been used to make chloroform and was the basis for the original bleaching powder process. 2. From methane by chlorination As described in Module:5, Lecture:29 Storage and handling All person should be instructed and supervised in appropriate method while handling chloroform to prevent the exposure. Proper supervision should be given while disposing this chemical. It should be stored and place in cooled in place. Dark green glass containers should be used for storage of this chemical. Bulk storage containers should be proper galvanized. The storage tanks should be equipped with vent dryer which is packed with calcium chloride. It can be transported via trucks, rail cars, ships and drums. Health and safety Due to inhalation of chloroform liver and kidney get damaged. This is NPTEL 3 Module:5 Lecture:30Chloroform Dr. N. K. Patel the principal hazard of chloroform. If the concentration of chloroform inhaled more it leads to unconsciousness and disturbance in equilibrium, upon coontct with skin it irritates to skin as well as affect the mucous membrane but still it is believed that medically significant quantity of chloroform are not affect through skin contact. Chloroform was first used as surgical anesthetic in the past years. But later it was abandoned as narcotic concentration always leads to death. Chloroform was also banned by FDA for use in various foods. Repeated contact with skin and clothes results into inflammation. In open flame, at elevated temperature, chloroform converts into the various product like phosgene, hydrogen chloride and chlorine etc. PROPERTIES Molecular formula Molecular weight Appearance Odour Boiling point Melting point Freezing point Density Vapour pressure Solubility : CHCl3 : 119.38gm/mole : Colourless liquid : Ethereal : 61.20C : -63.50C : -63.50C : 1.498gm/cm3 at 150C : 100mm at 10.40C : Miscible with alcohol, ether, benzene, Petroleum ether, oils,carbon disulfide and carbon tetrachloride USES Chloroform is used in a manufacturing of the chlorodifluoromethane which is precursor to tetrafluoroethylene As solvent in dyes, pesticides and pharmaceutical, rubber industry Used to bond pieces of acrylic glass As a solvent for rubber, fats oils, alkaloids, waxes, gutta-percha, resins As cleansing agent and as a fire extinguishers to lower freezing temperature of carbon tetrachloride For anesthetic application NPTEL 4
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