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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    talline precipitate. The addition of bichloride of platinum should always be preceded by that of hydrochlorie acid, to convert the potassium into chloride, if it should not exist already in that form. . 112. Cartmell* has proposed a very beautiful photo- chemical method for the detection of potash in the presence of soda; he views the blowpipe flame through deep blue cobalt glass;+ through this coloured glass no coloured rays from soda (or lithia) can pass, but it admits those peculiar to potash. Potash, viewed through this coloured glass, gives to the flame an intense violet colour ; and this is still visible when one part of potash is present with two hundred parts of soda. As all substances which make flame luminous, especially ali organic substances which burn with separation of carbon, give the same violet colour, these substances must first be removed by heat, before the colour of the flame can be used as a test for potash. Cartmell recom- mends Bunsen’s lamp as the blowpipe lamp to be used. 113. Sopa.—This alkali and its hydrate, on exposure to the air, attract moisture and become fluid; but in absorbing carbonic acid from the air, which it does very rapidly, it again becomes solid. The salts of this base, with a few exceptions, are very soluble; the means we have of detect- ing it are therefore limited. It exists in the mineral king- dom as cHLORIDE (kitchen salt), suLPHATE (Glauber’s salt), BORATE (borax or tincal), NITRATE, and CARBONATE. It likewise forms a constituent of many SILICEOUS MINERALS. 114. The best test for soda is the blewpipe flame, to * “Philosophical Magazine,’ 1858. t The cobalt blue glass can be obtained at the operative chemists. Before using the glass, it must first, of course, be ascertained how small a quantity of potash mixed with soda (or lithia) it will clearly indicate. 3