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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    surface of the latter as to obtain a clear, unbroken flame. A weak blast of air is only required for the reducing flame, but a strong blast is required for the oxidizing flame. 59. The colour of the reducing flame is bright yellow if an oil lamp or candle is used; but if gas is used, it should be of the same blue colour as the centre of the oxidizing flame. The colour of the oxidizing flame in all cases is a pale-blue colour, almost invisible by daylight. 60. “ When any substance is submitted to the action of the reducing flame, it should be so held as to be entirely surrounded by the reducing flame, and protected from the oxidizing action of the surrounding atmosphere; but this condition being fulfilled, it should be held as near as possible to the point of the flame, in order to gain the greatest amount of heat, and prevent any deposition of soot, which would shield the substance from the action of the flame, and would be occasionally attended with other disadvantages.” 61. When a substance is submitted to the action of the oxidizing flame, it should be held just beyond the point of this flame if a candle or oil lamp is used; butif gas is used, it should be held at a considerable distance(viz., one halfto three quarters of an inch) beyond the point of the visible flame.* 62. “ As the current of air which is supplied ought to be continuous, its production requires some attention and address. The air is not blown directly from the lungs, but is forced from the mouth by means of the cheeks. The difficulty consists in inspiring and expiring through the nose, while a continued stream escapes from the mouth. This may be attained by attention to the following direc- * In order to exercise himself in the manipulation of the blowpipe flame, the student will do well to practise the reactions afforded by the oxides of manganese and copper, as described in the par. “On the Treatment with Borax,” and the corresponding part of the table on blowpipe operations,