1872.] Capt. W. A. Ross on Pyrology s or Fire Analysis. 



453 



once prepared in this war, sulphur has uo further tendency to burn, and 

 it then has the remarkable property of giving, in a glass of phosphoric 

 acid, reactions similar to those of copper, viz. green hot, and blue-green 

 cold after treatment with a peroxidating pyrocone (to be hereafter de- 

 scribed) ; but green hot and cold after a reducing pyrocone has been ap- 

 plied*. Ultramarine might owe its blue colour to this fact. 



18. When a roundish mass of silica or alumina, or of both combined, is 

 held in the hydrocarbonous pyrocone, it becomes quite black ; and as this 

 blackness is not merely on the surface, but throughout the mass, it would 

 appear to be due to a decomposing effect exerted by the latter upon the 

 pyrocone itself, and not a mere deposition of soot, which might have been 

 supposed to have been mechanically carried along by the blast upon^its 

 surface. Alumina, however, appears to become partially fused, and thus 

 forms into roundish or botryoidal swellings, whiie silica presents a steel 

 black mass to the lens with shining metallic-looking points in it. These 

 two omnipresent and almost universally combined earths, therefore, may 

 be thus pretty correctly and extremely rapidly distinguished f. 



Alkaline Earths in H. P. 



19. Lime, strontia, and, to some extent, baryta and magnesia are not 

 thus carbonized by treatment with the hydrocarbonous pyrccone, and may 

 therefore when pure, be easily thus distinguished from the two first-men- 

 tioned earths. For lime, especially, a quantitative assay may be approxi- 

 mately made by slaking the mass thus treated in distilled water, when it 

 will remain dark or grey or white, according as the lime exists in lesser or 

 greater proportion. Above 80 per cent, of lime will cause the mass to re- 

 main perfectly white. The oxide of iron does not interfere with this reaction. 



20. This property, which lime possesses, of remaining perfectly white 

 and of resisting all tendency to reduction during such treatment, renders 

 it an excellent medium for the detection of chlorides and fluorides, which 

 seem to separate after a time from the lime, and to form some combination 

 with the carbon of the pyrocone, the lime having no such tendency ; for 

 instance, in chloride of calcium, after a few minutes of this treatment, a 

 small black patch, round in proportion to the sphericity of the mass, is 

 formed on the side next the current of blue flame, which can be easily seen 

 through the lens to be not soot, and seems to have a sweet taste ; but if 

 such a mass be often quenched in distilled water, and as often re- treated in 

 the hydrocarbonous pyrocone, the black patch will shortly assume a 

 metallic and white appearance. 



21. Fluorides after the above treatment exhibit an irregularly shaped 

 patch, also next the direction of the hydrocarbonous current; but this 

 patch, instead of being black, has a changeable green colour like some of 



* These effects are only in part producible by a gas-pyrocone. Vide paragraphs 4 & 7. 

 f The writer, by compressing the tip of the platinum jet so as to form a slit there, 

 instead of a round orifice, produced a Tery perfect H. P. 



