The elements of materia medica and therapeutics . in checking the frothing by breaking the bubbles. But the simplest,cheapest, and often the most useful form of apparatus, is a two-ounce wide-mouthed phial, with a cork perforated by a glass tube or tobacco-pipe (as infig. 115). It presents this great advantage, that we can employ a fresh apparatusfor every experiment, and thus avoid all possibility of contamination fromarsenical liquids used in previous experiments. y. If arseniiiretled hydrogen be subjected to a red heat it is de-composed into arsenicum, which is deposited, and hydrogen gas,w
The elements of materia medica and therapeutics . in checking the frothing by breaking the bubbles. But the simplest,cheapest, and often the most useful form of apparatus, is a two-ounce wide-mouthed phial, with a cork perforated by a glass tube or tobacco-pipe (as infig. 115). It presents this great advantage, that we can employ a fresh apparatusfor every experiment, and thus avoid all possibility of contamination fromarsenical liquids used in previous experiments. y. If arseniiiretled hydrogen be subjected to a red heat it is de-composed into arsenicum, which is deposited, and hydrogen gas,which escapes. The gas may be generated in a double-neckedbottle, or in a wide-mouthed bottle, closed by a cork bored with twoholes ; and may be allowed to escape by a horizontal tube (made ofdifficultly fusible glass), which may be heated by a large-wickedspirit lamp. The gas is decomposed by the heat; and the arsenicum 632 ELEMENTS OF MATERIA MEDICA. is deposited in the form of a metallic ring, beyond the flame and nearerthe aperture. Fig. Apparatus for subjecting Arseniuretted Hydrogen to the action of Heat or Nitrate of Silver. a. Bottle for generating the arseniuretted hy- drogen. b. Funnel, or tube, by which the sulphuric acid and arsenical liquor are introduced into thebottle. c. Escape tube, supplied with a bulb, to con- dense any liquid which may rise from thebottle. d. Wider tube, loosely filled with asbestos, to impede the passage of any water. This isnot essential. e. Narrow tube of difficultly fusible glass, drawnout to a fine point at the extremity. /. Spirit lamp. g. Curved and perforated metallic plate (copper,zinc, or tinned iron), to support the glass-tube in the event of its softeningby the heat. h. Curved glass-tube, which may be substitutedfor the tube e, when the gas is to be passedthrough a solution of nitrate of silver. i. Test-glass, containing a solution of nitrate ofsilver. The detection of arseniuretted hydrogen by heat was suggested by Liebig &
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