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.

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    408. When testing for the bases, we always find the chromic acid as sesquioxide of chromium, since hydrosul- phuric acid reduces it to that state. SutpHuric Actp (Oil of Vitriol) (HO, SO,). 409. Anhydrous sulphuric acid (SO5) is a white feathery crystalline mass, which, when exposed to the air, emits dense white fumes. It is destitute of acid properties until it has combined with water and passed into the hydrated state. The hydrated acid is a heavy, colourless, oily fluid, which possesses a strong affinity for water, producing, when mixed with it, a great degree of heat. Its affinity for water is so great, that it decomposes organic substances when placed in contact with them, removing their hydrogen and oxygen, whilst the carbon is left behind as a black coaly mass, a portion of which dissolves in the acid and communicates to it a brown tint. If heat is applied, the carbon is oxidized at the expense of the sulphuric acid, carbonic acid and sulphurous acid being formed: these facts may be illus- trated by pouring some strong sulphuric acid upon white sugar. Sulphuric acid, at temperatures below its boiling- point (572° F), displaces all other acids from their combi- nations with bases, but above that temperature it is itself displaced by the non-volatile acids. 410. Most of the sulphates, with the exception of the sulphates of baryta, strontia, and lead, are soluble in water. The alkaline sulphates and the three just named are the only salts of this acid which are not decomposed on simple ignition. 411. Sulphates in dilute solutions containing organic matter are gradually converted into sulphides. Water con- taming a sulphate may therefore, after it has been kept a long time in a bottle or any closed vessel, be found to con-