1872.] Capt. TV. A. Ross on Pyrology, or Fire Analysis. 



455 



or black, proceeds from the cobalt solution only, and not from any of the in- 

 gredients;" from which statement it is evident that we have hitherto lost some 

 of the most valuable qualitative indications of cobalt, due to the important 

 fact that lime and strontia are rendered caustic by much less heat than the 

 other " earths," and therefore dehydrate the cobalt solution after treat- 

 ment with a hydrocarbonous pyrocone, rendering it blue, which none of 

 the other earths will do. If the colours " proceed from the cobalt solution 

 only," how is it that lime turns blue and baryta red when it is thus 

 applied ? 



Fish-tail Flames. 



25. If a pyrochromatic substance be held on the loop of a platinum- 

 wire in a rapid hydrocarbonous current, produced by blowing strongly, the 

 current is broken upon it so as to form a kind of fish-tail flame at its rear, 

 i. e. the side turned from the base of the pyrocone, in the blue matter of 

 which its front is enveloped as usual. The inner sides of this fish-tail 

 flame will, after a short time, be observed to be deeply and continuously 

 tinged with the colour which is the chief characteristic of the substance 

 burned*. A far stronger pyrochromatic reaction is thus obtained than by 

 holding the substance in the position usually adopted, of what is called " the 

 point of the outer flame," or, in fact, in an oxyhydrogen pyrocone ; for 

 here the superposed blast is too violent, and carries away the colour as soon 

 as formed. 



The Oxyhydrogen Pyrocone. (0. P.) 



26. In which the object is held as at a, fig. 1 . It is commonly called " the 

 oxidating, oxidizing, or outer flame but that the two first of these ap- 

 pellations are incorrect is shown by the fact that when some metallic oxides, 

 as those of gold, silver, or mercury, dissolved in a flux more delicately 

 sensible to oxidation and reduction than borax or microcosmic salt, viz. 

 phosphoric acid, are held in this position, the bead, so far from being 

 further oxidized, immediately precipitates its contents, and becomes dim or 

 opaque in consequence. 



2". This pyrocone appears to be caused by the intermingling of the two 

 currents — of air and ignited hydrocarbonous matter, its broadest part being 

 at a, where they may be supposed to cross each other, giving it a slightly 

 oblate appearance. 



The Percxidizing Pyrocone. (P. P.) 



28. In order to produce the full effect of this pyrocone, the object must 

 be held at a distance of three inches from the point of the blue. It can be 

 produced, but not long sustained, by the mouth, as a very strong blast is 

 necessary to impart sufficient heat to an object at such a distance (3, fig. 1). 



The Bunsen Blowpipe. 



29. Before leaving the subject of pvroconcs, it is necessary to mention 



* The substance should occasionally be dipped in distilled water, 



