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.

    183/272 (page 165)
    tain sulphuretted hydrogen, although originally it was per- fectly free from that gas. 412. Sulphate of baryta, from its insolubility in aecds, is at once distinguished from all the other baryta salts ; any soluble salt of baryta is therefore the best and most delicate test for SULPHURIC ACID. 413. Insoluble sulphates are completely decomposed by fusion with alkaline carbonates, an ALKALINE SULPHATE being produced along with a CARBONATE or an OXIDE of the METAL. 414. When a sulphate, mixed with eharcoal and carbo- nate of soda, is fused upon a charcoal support by the inner blowpipe flame, sulphide of sodium is produced. If the fused mass, moistened with water, be placed upon a piece of silver, a brown stain of sulphide of silver will be formed. Boractc Actp (BOQ,). 415. This acid is best obtained by adding to a boiling concentrated solution of biborate of soda (borax) strong sulphuric acid, until the liquor becomes sour to the taste : on cooling, the greater part of the boracic acid separates from the solution in the form of colourless crystalline scales, containing water. When ignited, they fuse to an anhy- -drous glassy mass, which, on exposure to the air, absorbs water, swells, and becomes opaque. This acid, in the anhy- drous state, is a colourless fixed glass, fusible at a red heat ; the hydrate (2 BO,, 3 HO) is a porous white mass; in the crystalline state (2 BO,, 83 HO +3 aq.) it presents small scaly lamine. The hydrated acid is much more soluble in hot than cold water. When an alcoholic or an aqueous solu- tion of this acid is evaporated, a portion of the acid vola- tilizes with the vapours of the solvent, but alone it is per- fectly fixed at a red heat. One peculiar property which