The use of the blowpipe, in the qualitative and quantitative examination of minerals, ores, furnace products and other metallic combinations / Edited, with emendations, by Dr. Sheridan Muspratt. With a preface by Baron Liebig.

  • Plattner, Carl Friedrich, 1800-1858.
Date:
1850
Catalogue details

Licence: Public Domain Mark

Credit: The use of the blowpipe, in the qualitative and quantitative examination of minerals, ores, furnace products and other metallic combinations / Edited, with emendations, by Dr. Sheridan Muspratt. With a preface by Baron Liebig. Source: Wellcome Collection.

    67/440 (page 43)
    triturating pieces of charcoal in a mortar. It is generally employed for roasting or smelting, in quantitative tin or lead examinations. 25. Graphite (Plumbago). — It is used quantitatively, when free from impurities, for roasting earths, minerals, and various products, upon copper. When a good kind of graphite cannot be obtained, pure anthracite may he substituted. The graphite which is generally met with is so impure, that an operator, to get the best pieces, must pick from a mass of it those fragments which are unctuous to the touch, and in scales. These parts are then heated in a crucible, and afterwards well pulverized. If this graphite contains over ten per cent, of foreign matter, it must, previously to being used, he digested in nitro-hydrochloric acid (aqua regia), to free it from iron and other impurities.* 26. Tin, — Tin foil is generally used, cut into little slips, half an inch broad, and tightly rolled. Tin serves for the highest degree of reduction in glass fluxes, where small quantities of oxides of the metals are present, which are capable of being reduced to a lower state of oxide, in which state the results are more convincing. The operator brings the globule, heated in the reducing flame, in contact with the free end of a rolled rod of tin. By this means a small portion of melted tin is deposited upon the flux. The whole is then fused perfectly in the reducing flame. When the tin has been added to the bead, which contains the substance for examination, an operator must not direct the flame upon the glass for too long a time, partly because the tin would become in such a state as to prevent metallic oxides, which should only he reduced to the state of protoxide, from manifesting their presence by the peculiar color imparted to the head, or pearl, and partly because so * [Plumbago is extensively used for the manufacture of crucibles, espe¬ cially those required for the purposes of the Mint, as they are very durable, and sustain an intense heat. The composition of the plumbago of Cornwall is, according to Saussure, 96‘0 carbon, and 4*0 iron.—£'d.]