Blowpipe practice; an outline of blowpipe manipulation and analysis, with original tables for the determination of all known minerals . powder will present a dullearthy aspect, and cease to omit fumes or odour. It is then readyfor Operations 7 and 8, described below. By reducing the substanceto powder before roasting, the risk of decrepitation and fusion is pre-vented, and the process itself is more efficiently performed. (5) Treatment in Open Tube.—Roasting is sometimes effected in apiece of open glass tubing, as in Fig. 11, the test object being placednear one end of the tube, whilst the tub
Blowpipe practice; an outline of blowpipe manipulation and analysis, with original tables for the determination of all known minerals . powder will present a dullearthy aspect, and cease to omit fumes or odour. It is then readyfor Operations 7 and 8, described below. By reducing the substanceto powder before roasting, the risk of decrepitation and fusion is pre-vented, and the process itself is more efficiently performed. (5) Treatment in Open Tube.—Roasting is sometimes effected in apiece of open glass tubing, as in Fig. 11, the test object being placednear one end of the tube, whilst the tube itself is held in an inclined position. For the better retentionof the substance, the tube may besoftened at this end in the flameof the spirit-lamp, and then bentinto a slight elbow. Sulphureliminated from bodies by thistreatment, is converted into sul-phurous acid (a compound of sul-FlG- 11- phur and oxygen, the latter taken up from the atmosphere); and arsenic forms arsenious acid, whichdeposits itself in the shape of numerous microscopic octahedrons onthe cool sides of the glass near the upper part of the tube. Sulphurous. 12 BLOWPIPE PRACTICE. acid in escaping from the open end of the tube is easily recognizedby its odour (identical with that emitted by an ignited match), as wellas by its property of changing the blue colour of a slip of moistenedlitmus paper to red. Antimonial compounds form a dense whiteuncrystalline sublimate. (6) Treatment with Nitrate of Cobalt.—This operation is required inspecial cases only. It serves for the detection of alumina, magnesia,oxide of zinc, and some few other substances ; but it is not applicableto deeply coloured or easily fusible bodies, nor to such as possess ametallic lustre or coloured streak. A fragment of the substance,under treatment, is reduced by the hammer and anvil, and afterwardsby the use of the agate mortar, to a fine powdei\ This is moistenedwith a drop of the cobalt solution (nitrate of cobalt dissolved in water)
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishertorontocoppclark
