Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays.

  • Albert Bernays
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: Notes on analytical chemistry for students in medicine : extracted from the fifth edition of "Notes for students in chemistry" / by Albert J. Bernays. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    146/182 (page 134)
    1 34 ALCOHOLIC EX.THACT IN BEEIfS. ANALYSIS OF WATERS. 6. 25 c.c. evaporated to a syrup, stirred well with 10 c.c. rectified spirit, the latter filtered and gently evaporated gives alcoholic extract. Notice its color, whether soluble in water (separation of resin), its taste—bitter, nauseous, salty, &c. The taste of licorice comes out strongly. Hop gives a strong and pleasant bitterness, with a good deal of resin. 7. Examine sediment under microscope. [For further details, see Blyth's Food Analysis.] DIALYSIS. Liquid diffusion is the property which many substances, when dissolved, possess of passing through membrane. The majority of inorganic soluble substances, and a large number of the simpler organic compounds, are crystallizable and diffusible, and are called crystalloids. But viscous and albuminous bodies do not diffuse: they are called colloid (or glue-like) substances. Silicic acid gives a fair idea of a colloid. A dialyser is a cylinder, open above, and closed below by a diaphragm of vegetal parchment or bladder, suspended so that the diaphragm just dips into a large basin of distilled water. The mixture to be examined is poured into the cylinder : on standing, the crystalloids diffuse through into the water, while the colloids remain above the membrane. In this way arsenic, strychnia, and other crystalline poisons may be separated from an animal liquid such as blood, or a stomach contents. On evaporating the distilled water, the crystalloid may be recovered almost pure. Arsenious acid must be neutralized before evaporation, to avoid volatiliza- tion with the steam. ANALYSIS OF POTABLE WATERS. A Winchester quart (half a gallon), in a perfectly clean bottle, should be collected. Color. Place in a tall cylinder of colorless glass, and look down on to a sheet of white paper. Pure water has a bluish tint; marsh waters are brown : contamination with sewage gives a yellow coloration; alga? give a greenish tinge. Chalk waters often have a white turbidity, clay waters a brown, ferruginous waters a reddish brown, or a brown, flocculent sediment. Sediment. Allow to stand in a large conical glass, pour off the water, and examine the deposit under the microscope. Odor. Half fill a flask with the water, warm, shake vigorously and smell. A marshy, or even a fetid or urinous, odor may be detected.