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To Concentrate Acetic Acid

by steam. The evolved nitrous vapors are Acid containing 20 per cent. of water may be usually allowed to escape, but if conveyed deprived of a good deal of its superfluous into a chamber filled with cold damp air, and water by standing over dry sulphate of soda . containing a little water, they will absorb It may then be used either with or without oxygen, and be recondensed into fuming distillation. Acetic acid of ordinary strength nitric acid. In England an equivalent promay be concentrated to any degree of rectifiportion of molasses is usually substituted for cation once or oftener from dry acetate of posugar. Another process consists in first contassa or soda, rejecting the first and last porverting potato fecula into grape sugar with tions that come over. The same acetate may be used repeatedly. The heat employed must not exceed 500 to 570° Fahr. Pure hydrated acetic acid liquefies above 62° Fahr.; at 50° to 55° it crystallizes in brilliant, colorless, transparent needles and plates; at 40° it is a cryssolid. Free acetic acid reddens litmus paper, and may be recognized by its odor and volatility. sulphuric acid, and then decomposing the sugar thus obtained by nitric acid, in the usual way . Dr. Ure recommends the use of a little sulphuric acid along with the nitric acid , which, he says, contributes to increase the product; 15 pounds of sugar yielding fully 17 pounds of crystallized oxalic acid. 3902. Dale's Process for Obtaining Oxalic Acid. At present much of the oxalic

3899. Tests for the Purity of Acetic acid of commerce is obtained by heating saw- Acid.

By heat it escapes entirely in vapor. dust with a mixture of 2 parts caustic soda Either nitrate of silver or chloride of barium with 1 part caustic potassa. A watery solution being added to it, will produce no precipitate. of the mixed alkalies is evaporated to specific When a thin plate of silver is digested in it, gravity 1.35, and then mixed with sawdust and hydrochloric acid subsequently dropped to a paste. This is heated on iron plates to in, no precipitate is formed. Its color is un- 400 Fahr., and kept at that temperature for 1 changed by the addition of hydrosulphuric or 2 hours, with constant stirring; the heat is acid, or ammonia, or by ferrocyanide of potascontinued until the mass is quite dry, but not sium added after the ammonia: The presence charred . It now contains 28 to 30 per cent. of sulphuric acid is indicated by a white pre- of oxalic acid combined with the alkalies. By cipitate being formed on the addition of a lit- washing the powder on a filter with a solution tle peroxide of lead.