Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![§ 90. I. Soda, NaO [Na,,0]. 1. 8oda and its hydrate and salts have in general the same properties and reactions as potassa and its corresponding compounds. The oily Kquid which soda forms by deliquescence on exposure to the air resohdifies speedily by absorption of carbonic acid. Carbonate of soda crystallizes readily; the crystals, NaO,CO,+ lOaq [Na,CO3,10H,O], effloresce rapidly when exposed to the air; the same applies to the crystals of sulphate of soda, NaO,SO, + lOaq [Na,SO„10H,O]._ 2. If a sufficiently concentrated solution of a soda, salt with neutral or alkaline reaction is mixed, for greater convenience, in a watch-glass, Avith a solution of metantimonate of potassa prepared according to the directions given in § 51, the mixture remains clear at first, or appears only shghtly turbid; but upon rubbing the part of the glass wetted by thehquid with a glass rod, a crystalline precipitate of metantimonate of soda, NaO,HO,Sb03 + 6aq [Na^H.SboO^SH^O], speedily separates; this makes its appearance first along the lines rubbed with the rod, and ultimately subsides as a heavy, sandy precipitate. The precipitate does not separate from dilute solutions of soda salts until after the lapse of some time, occasionally as long as twelve hours. From very dilute solu- tions, it does not separate at all. The precipitated antimonate of soda is invariably crystalline. Where it has separated slowly, it occasionally consists of well-formed microscopic cubic octahedrons, but more fre- quently of four-sided prisms with pyramidal summits; if it has se^ parated quickly, it appears in the form of small boat-shaped crystals. The presence of large quantities of salts of potassa interferes very con- siderably with the reaction. Acid solutions cannot be tested with met- antimonate of potassa, as free acids will separate from the latter sub- stance hydrated metantimonic acid. It is indispensable, therefore, before adding the reagent, to remove, if possible, the free acid by evaporation or ignition, or where this is not practicable, by neutralizing the acid solution with a little carbonate of potassa until the reaction is feebly alkaline. It should also be borne in mind that solutions cannot be tested with metantimonate of potassa if they contain any other bases besides soda and potassa. 3. If salts of soda are held in the fusing zone of the Bunsen gas- lamp or in the inner spirit blowpipe flame, they show, with regard to their relative volatility and the action of decomposing agents on them, a similar behaviour to the salts of potassa; the soda salts, are, however, a little less volatile than the corresponding potassa salts. But the most characteristic sign of the presence of soda salts is the intense yellow coloration which they impart to the flame. This reaction will effect the detection of even the minutest quantities of soda, and is not obscured even by the presence of large quantities of potassa. The spectrum (see coloured plate) shows only a single yellow line a in an ordinary spectroscope, but with a more powei-ful apparatus two lines will be visible distinctly, although they are exceedingly close to each other. The reaction is so delicate that the chloride of sodium contained in atmospheric dust generally suffices to give a soda spectrum, although a faint one.](https://iiif.wellcomecollection.org/image/b21966953_0111.jp2/full/800%2C/0/default.jpg)
