Exercises in practical chemistry. Series I : Qualitative exercises / by A.G. Vernon-Harcourt and H.G. Madan.

  • Madan H. G. (Henry George), 1838-
Date:
1869
Catalogue details

Licence: Public Domain Mark

Credit: Exercises in practical chemistry. Series I : Qualitative exercises / by A.G. Vernon-Harcourt and H.G. Madan. 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.

    286/394 (page 266)
    organic substances (not, however, acetates) turn black when thus treated. (F) The substance does not become charred, but evolves a gas, with or ivithout previous fusion. This gas is— (a) Colourless, and has the peculiar suffocatiiig smell of sulphur dioxide, and reddens a piece of blue litmus-paper held in the mouth of the tube. This indicates the presence of a sulphate de- composable by heat. (/3) Colourless, and has the peculiar smell of cyanogen, re- sembling bitter almonds. Hold a lighted match to the mouth of the ■*-*^* tube. If the gas burns with a pink flame, a CYANIDE is present. (y) Colourless and odourless. Place a single drop of lime water on a watch- glass, and hold it close to the mouth of the tube (which should be as far as possible from the lamp-flame). If the drop becomes turbid, the gas is caebon dioxide, and pro- ceeds from the decomposition of a cakbonate or an oxalate. If carbon dioxide is not detected, drop a small splinter of charcoal from the charred end of a match into the tube, and again heat the end of the tube. If the charcoal burns vividly, the gas is oxygen- and the substance is a CHLOBATB, NITRATE, CHEOMATE, Or PEROXIDE^. (S) Orange-coloured, and reddens litmus-paper. The sub- stance is probably a nitrate; if so, a splinter of charcoal dropped into the tube will deflagrate as in the case of chlorates. Some few bromides and iodides are decomposed by heat alone, and give off orange vapours of bromine, which con- dense to an orange liquid, or violet vapours of iodine, which condense in the form of steel-grey flakes. [Hypophosphites, when heated, give off hydrogen phos- phide, which inflames spontaneously at the mouth of the tube.] 1 Ammonium ohromate, however, gives off, not oxygen, but w.^tei- and nitrogen, and a light, bulky, olive-green residue of chromium o>dde is left.