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
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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.

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    ON TESTING SOLUTION'S OF ALKALINE SUBSTANCES. specific heat of mercury. Each element has its own specific heat, and this is, generally, inversely as their atomic weights. But, if instead of com- paring equal weights of the elements with an equal weight of water, we take the atomic weights of the elements, the elements have, for the most part, the same atomic heats. The atomic heats of most of the elements may be taken as 64, and they are obtained by multiplying the specific heat of each element by its atomic weight. Water is the great solvent. As a rule, the lower the temperature, the larger the amount of gases soluble in water. Equally, as a rule, the higher the temperature of water, the greater is its solvent power upon solids. OF SUBSTANCES IN SOLUTION. Now study the reactions with Test-2>apers, especially with red litmus and blue litmus. A. Eed litmus is turned blue: solution is alkaline. B. Blue litmus is reddened: solution is acid. C. Test-papers are unchanged: neutral. A. THE SOLUTION IS ALKALINE : red litmus is blued. If an alkaline solution contains free Ammonia, or Carbonate of Ammonium, the Ammonia will be recognised by the smell. If the alkaline solution contains a Sulphide, there will be the odor as of rotten eggs. If the alkaline solution contains a Cyanide, there will be a smell of prussic acid. a. To a portion in a test-tube, say 20 drops, add a solution of Carbonate of Sodium Na2C()3: a careful observation of results is of first importance. I. No precipitate in the alkaline solution, and no smell of Ammonia NH3, even on boiling, would indicate either Potassium hydroxide KOH, Sodium hydroxide NaOH, or Salts of Potassium, or Sodium, with alkaline reaction. [Carbonate of Potassium KaC03, Carbonate of Sodium Na2COs, and Carbonate of Am- monium (NH4)2C03, are very soluble in water, and turn litmus paper blue.] II. No precipitate with Sodium carbonate Na2C03. but a smell of Ammonia Nil,, without, or with heating, would indicate a solution of Ammonium hydrate NH4OH, or some Salt of Am- monium with alkaline reaction. III. A white precipitate with Sodium carbonate Na2C03, in the alkaline solution, points to the Hydroxides or Hydrates of Barium Ba(OH)2, Strontium Sr(OH)2, or Calcium Ca(OH)2. [Barium carbonate BaCOs, Strontium carbonate SrC()s, and Calcium carbonate CaCO„ are practically insoluble iu pure water: they are precipitated from any of their soluble salts by solution of Carbonate of Sodium. Thus: