Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

    23/272 (page 5)
    action is clearly perceptible with a very minute quantity of the substance tested for. The student must be very par- ticular in always mixing thoroughly the reagent with the solution te which he has added it, and not simply content himself by adding it (as is generally the case with begin- ners), without attempting, by agztation, to incorporate the two fluids. The way for mcorporating them has been fully described in the first experiment (par. 9); it only remains for us to guard the student against the accident of losing the liquid, which is likely to occur, when the liquid is hot, unless the operator keeps his thumb firmly fixed upon the mouth of the test-tube; because the air in the upper part of the test-tube, in passing over the heated liquid, becomes expanded, and would therefore expel the liquid, unless the mouth of the tube was kept firmly closed. 13. If to any salt of ammonia one of the soluble bases is added, the latter will deprive the ammonia of its acid ; consequently, the ammonia will be set free, which will be perceived by the smell. The soluble bases set the ammonia free from its salts in the solid state, as well as in solution ; heat assists the liberation in each case. If, to any salt of the volatile acids, an acid having a stronger affinity for the base of the salt is added, the volatile acid will be set free ; the deeomposition takes place as well when the salt of the volatile acid is insoluble as when it is soluble, in water. The following experiments illustrate the principles here stated. EXERCISES. 14. Dissolve two or three grains of chloride of ammo- nium in a test-tube containing water; add to it some caustic soda solution, and then warm the liquid in the tube; ammonia will be set free in the gaseous state. It will be known, when it is in the free state, by the smell.