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8G BLOWPIPE. chemical composition is inferred from the various appearances which present themselves. The assay may be heated alone, in a glass tube closed at one end over the flame of a spirit-lamp, in order to discover whether any thing 1S volatilized without free access of atmos- phene air. By this experiment it may be ascertained whether water, mercury, arsenic, tellurium, and, in many cases, whether sulphur or fluorine are present in the mineral. e assay is heated alone, in a glass tube open at both ends, m or er o see whether, when freely exposed to the air, vola- tile oxides or acids are formed and expelled. In this manner, or examp e, most of the compounds of sulphur, selenium, tel lurium, and arsenic may be recognized. ' e assay is heated on charcoal in order to discover the qpW; Ue0 r ar ff mc ( lu the illn er flame), or of sulphur and selenium ( m the outer flame), which betray themselves by , S / Antimony, zinc, lead, and bismuth are known by eposit that is formed upon the charcoal round the assay, any oxides and sulphurcts are reduced to a metallic state. ie assay is heated alone in the forceps, on platinum wire, or fk- ’ determine its fusibility; other appearances, such i j g ’ intumescence, shining, colour of the flame, are to he noted at the same time. Minerals differ extremely in their fusibility. Some melt rea i y m large grains ; others more difficultly; others, again, on y in fine splinters; and many are perfectly infusible before' e blowpipe. The nature of the result of fusion is also to bo o served, whether it appears as a glass, clear, or full of bubbles as enamel, or as a slag. v. Kobell expresses the degree of iw°x. a nimeral numerically, by comparing its fusibility that of one of the minerals in the following scale :— ntimomte, (2) natrohte, (3) almandine, (4) actynolite, (o) orthoclase, (e) bronzite. , f most important reagents used in testing minerals with the blowpipe are the following koda (carbonate of soda) is used for dissolving silica and j - SI lea te s i and the reduction of metallic oxides. 1'or wiHi 1C Jqlo’ 't aS8a - y ground to powder, made into a paste ,1 , ’ an ex P°sed to the inner flame on charcoal. Usually into lUt °, t] i e charcoilL The P ortion of charcoal verv firm ‘ . | 6 S °- ! s penetrated must be reduced to a coafdii8t P " imi 1 'y a ter, in an agate mortar, and the char- reducible HI W. Jf the as3a y conta iued a or nowder n ’V " * behind in the mortar in spangles S ^r * ng M th<? m0tal is or is malleable 1 Fre- of Potassium for reduc^g^etalhc'oUdes!^ 61 C ^' all ^ e
