128 TERMINOLOGY* 



which is best obtained by the aid of one of the finest appendages, the 

 opening of which should be introduced only within the edge of the 

 flame. A less distinctly blue cone than in the former instance, sur- 

 rounded by a more brilliant one, will be the result. The matter to be 

 deoxidized is to be supported completely within the bright flame, just 

 beyond the apex of the blue cone : this medium consists of an inflam- 

 mable gas not yet saturated with oxygen, and which, of course, will seek 

 it from the matter of assay. 



The ordinary support for the substance placed before the blowpipe is 

 well burnt charcoal. In its selection, it is important to attend to the cir- 

 cumstance of its being freshly burned, and that it be of a light texture ; 

 as the more compact charcoal, besides being too good a conductor, is in- 

 convenient on account of the large quantity of ashes it produces, Gahn 

 preferred charcoal from pine wood. Platina wires three or four inches 

 in length, are employed in those cases where the reducing effect of a 

 charcoal support is liable to prevent the reaction which we wish to pro-, 

 duce. The matter of assay is easily attached to the wire, by bending 

 up one extremity into a hook, moistening it with the tongue, and dip- 

 ping it into the powdered flux we have occasion to employ, which ad- 

 heres to it in sufficient quantity : it is now brought before the flame of 

 the blowpipe where it melts into a drop, and this being brought near the 

 matter of assay, they immediately unite and are melted together. In 

 those instances where it is requisite to roast the matter of assay in or- 

 der to discover the substances with which it is engaged, little tubes of 

 glass two or three inches in length and about one tenth of an inch in di- 

 ameter, are employed. The substance to be examined is introduced into 

 the tube and placed at a little distance from one of its extremities, in- 

 clining the tube so that this extremity shall be the lowest: the flame of 

 a spirit of wine lamp i? now gradually brought to bear upon the tube 

 by means of the blowpipe, and in such a manner that the flame shall 

 play around the part containing the matter of assay : the volatile matters 

 sublime into the upper part of the tube, where they are in part con- 

 densed and capable of being recognized. Occasionally in these trials, it 

 is convenient to have a tube closed at one extremity : this is easily pre- 

 pared from open tubes by the aid of the blowpipe. 



The reagents most commonly used with the blowpipe, are the sub? 

 carbonate of soda, the borate of soda, and the double salt formed of the 

 phosphate of soda and phosphate of ammonia, which, for the sake of 

 brevity, are called soda, borax, and salt of phosphorus. The objects in 

 view, when the first of these is employed, are to ascertain if the bodies 

 combined with it are fusible or infusible, and to favor the reduction of 



