Text-book of medical and pharmaceutical chemistry / by Elias H. Bartley.

  • Bartley, Elias Hudson, 1849-1937.
Date:
1898
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Licence: Public Domain Mark

Credit: Text-book of medical and pharmaceutical chemistry / by Elias H. Bartley. Source: Wellcome Collection.

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    fumes strongly in the air, giving off a part of the gas. On being heated it gives off its acid rapidly. The commercial muriatic acid is yellow in color, due to the presence of ferric chloride. It also con- tains other impurities, and is used only for manufacturing purposes. The composition of the acid may be determined by means of the apparatus shown in figure 50, page 137. The apparatus is filled with the strongest commercial acid, mixed with ten volumes of a saturated solution of common salt, NaCl. The bind- ing-posts are connected with a battery of two Bunsen cups. The chlorine separates at the positive pole, and the hydrogen at the negative pole. The volumes of the two gases are equal. By the use of the apparatus shown in figure 51, we may arrive at the same result by synthesis. We introduce, through the stopcock at the top of the apparatus, equal volumes of hydrogen and chlorine. By opening the stopcock below, we draw off the mercury until the height of the column is the same in both limbs. On passing a series of sparks from an induction coil (Fig. 34) through the mixed gases, they combine, with an explosion. No contraction is observed. No excess of either gas is left, but a new gas has taken their place—viz., hydrochloric acid. (See p. 88.) Acidum hydrochloricum (U. S. P., Br.) is a colorless, fuming liquid, having a pungent odor and an intensely acid taste. Its sp. gr. is 1.163 at 150 C. (590 F.), and it contains 31.9 per cent, of abso- lute hydrochloric acid. Acidum hydrochloricum dilutum (U. S. P., Br.) is made by diluting the stronger acid with water. (Strong acid, 100 parts; dis- tilled water, 219 parts.) The sp. gr. is 1.050, and contains about ten per cent, of HC1. Pure hydrochloric acid should be colorless, and when diluted with distilled water should give no precipitate with H2S, NH4OH in excess, or BaCl2, and should not dissolve gold leaf (absence of HN03). Tests.—1. Heated with Mn02, it gives off chlorine. 2. Added to AgN02, it gives a curdy, white ppt., soluble in ammonia water but insoluble in nitric acid. AgN03 + HC1 = AgCl + HNO3. 3. Added to mercurous nitrate, it gives a white ppt., which is blackened by ammonia water. Hg2(NOs\ + 2HC1 = Hg2Cl2 -f 2HNO3. Hg2Cl2 -f 2NH4OH =NH2Hg2Cl -f NH4C1 + 2H20. Nitromuriatic Acid, Acidum Nitrohydrochloricum (U. S. P.).—(Aqua regia.) This is made by mixing 180 c.c. of nitric acid with 820 c.c. of hydrochloric acid, in a capacious glass vessel, and when effervescence has ceased, pouring the product into amber- colored glass-stoppered bottles.