Blow-Pipe Analysis baixar o livro de graça

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1875 Excerpt: ...detected by inserting a strip of moistened Brazil-wood paper at the open end of the tube. 2. When fluorides are heated in a glass tube with bisulphate of potash, hydrofluoric acid is given off. This etches the tube immediately above the assay, and gives the reactions with Brazil-wood paper just mentioned. 3. The best method for the detection of fluorine in all cases is to mix the assay with previously fused salt of phosphorus, and heat in the open tube in such a manner that the flame passes into the end of the tube. In this way hydrofluoric acid is formed; it may be recognized by its peculiar pungent odor and its corrosive action on the inner surface of the glass tube, rendering it opaque and lustreless at the points where moisture has condensed. For a confirmatory test the reaction with Brazil-wood paper may be employed. As the heat required in this experiment is so great that the glass tube often becomes soft and unmanageable, it has been recommended to use a piece of platinum foil rolled together and inserted into the end of the glass tube, as in Fig. 25. Fio. 2u. The substance to be tested is placed with the flux upon the projecting part of- the foil, and the flame directed as before. 115. Glucina gives no reactions which admit of being determined B. B. With certainty (see page 33). It is not of frequent occurrence, being only found in combination with silica and alumina. 116. Gold may usually be recognized by its physical characters. It is separated from the easily volatile metals by simple heating on charcoal in O. F. If associated with copper or silver, it must be fused with a large excess of metallic lead and subjected to cupellation (see 142). The copper becomes absorbed and passes off with the lead, while the silver remains alloyed with the g...