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To Prepare Citric Acid

Add 46 ounces chalk by degrees to 4 pints lemon juice, heated, and mix; set by, that the powder may precipitate; afterwards pour off the supernatant liquor. Wash the precipitated citrate of lime frequently with warm water; ployed in calico printing, and in medicine, as then pour upon it 274 fluid ounces diluted sulphuric acid and 2 pints distilled water, and and is much used by the calico printers. boil for 15 minutes; press the liquor strongly Sometimes a little nitric acid is added to the through a linen cloth, and filter it. Evapor- solution of the colored crystals, for the purate the filtered liquor with a gentle heat, and pose of whitening them, but in this way a set it aside that crystals may form. To obtain minute quantity of oxalic acid is formed. the crystals pure, dissolve them in water a Good lemon juice yields fully 5 per cent. of second and a third time; filter each solution, lemon acid, or 2 gallons yield about 1 pound evaporate, and set it apart to crystallize. The of crystals. If the imported citrate of lime preparation of citric acid has become an im- be used, a given quantity must be heated to portant branch of chemical manufacture, from redness, and then weighed, when the percentthe large consumption of this article in va- age of lime present will be ascertained; rious operations in the arts. In conducting every 28 pounds of which will require 49 this process some little expertness and care pounds of sulphuric acid of 1.845 (or a corresare necessary to ensure success. The chalk ponding quantity containing exactly 40 parts employed should be dry, and in fine powder, of dry acid) for its complete decomposition. and be added to the juice until it be perfectly 3934. Tests for the Purity of Citric neutralized, and the quantity consumed must Acid. When pure, it does not yield a crysbe exactly noted. The precipitated citrate of talline precipitate when added in excess to a lime should be well washed with water, and solution of carbonate of potassa; such a prethe sulphuric acid diluted with 6 or 8 times cipitate indicates the presence of tartaric acid. its weight of water, poured upon it while still It is entirely soluble in water, and what is warm, and thoroughly mixed with it. The thrown down by acetate of lead from this so- , and thoroughly mixed with it. The thrown down by acetate of lead from this soagitation must be occasionally renewed for 8 or lution. is entirely soluble in dilute nitric acid. agitation must be occasionally renewed for 8 or lution. is entirely soluble in dilute nitric acid. 10 hours, when the dilute citric acid must be No salt of potassa, except the tartrate, yields poured off, and the residuum of sulphate of a precipitate with the aqueous solution. It is lime thoroughly washed with warm water, entirely decomposed by heat; added sparingly and the washings added to the dilute acid. to cold lime water, it does not render it tur- The latter must then be poured off from the bid, and when a few drops of a solution of impurities that may have been deposited, and citric acid are added to lime water, a clear evaporated in a leaden boiler, over the naked liquid results, which, when heated, deposits a fire, until it acquires a specific gravity of 1.13, white powder, soluble in acids without efwhen the process must be continued at a fervescence. lower temperature until a pellicle appears