454 Capt. W. A. Ross on Pyrology, or Fire Analysis. [June 20, 



the aniline compounds, and, after some quenching with water, a metallic 

 appearance, but still green. 



22. A very curious result is obtained by the treatment of bicarbonate of 

 soda in the hydrocarbonous pyrocone. After a short time violent ebulli- 

 tion commences in the melted bead ; bubbles of some (carbonic acid ?_) gas 

 are seen to rise with great rapidity through it while red-hot. In this state 

 of violent ebullition, fragments are projected from the mass, which, when 

 examined through a lens, are found to be black hollow spheres like micro- 

 scopic shells. Notwithstanding the loss occasioned by the ejectment of 

 these projectiles, the mass, if now carefully examined by a lens, will be 

 found to consist partly of caustic soda, and partly of a black substance, 

 solid and even angular and shining like a piece of coal. This substance 

 is proved to be carbon by its deflagration when heated with nitre, and its 

 formation is proved to be not due to a deposition of soot from the lamp- 

 flame, by the fact that the similar treatment of chloride of sodium will pro- 

 duce no such result. 



23. If any of the "earths " be held on platinum-wire after being made 

 into a paste with a little distilled water in a hydrocarbonous pyrocone, 

 those which carbonize in such a situation, as alumina and silica, being 

 slightly heated in an oxidating pyrocone for a few seconds so as to just 

 burn off the carbon, and if the mass be then saturated with cobalt solution, 

 lime and strontia will immediately turn a distinct blue ; and of these two, if 

 allowed to remain exposed to the air for a time, the lime will slowly turn 

 green, the strontia brown*. The previous addition or existence of iron sesqui- 

 oxide will cause these to turn, instead of blue, green in the first instance. 

 All the other earths, if pure and not in a chemically caustic state, become 

 pink with cobalt solution ; and if then they are approached carefully to the 

 natural pyrocone of a spirit-lamp, this pink colour deepens to a rich 

 carminef. Of these earths, alumina and magnesia will (as is known), when 

 treated with a peroxidizing pyrocone, change, the first to a deep blue, the 

 second to a pale flesh or salmon-colour. Silica in this case turns a distinct 

 purple, even in presence of oxide of iron; lime, baryta, and strontia a grey 

 or grey-black. We thus obtain a nearly new chromatic series between the 

 common " earths" of considerable value in analysis, as follows : — lime (a) 

 and strontia (b) blue, changing on exposure to air (a) to green and (b) to 

 brown. Alumina (a), silica (6'), baryta (c), and magnesia (d') pink ; 

 changing on treatment with a peroxidizing pyrocone (a) to blue, (b') to 

 purple, (c) to grey-black, and (d') remaining pink. 



24. Berzelius, and after him Plattner and other writers on blowpipe ana- 

 lysis, tell us we " are not to take notice of any changes of colour in a 

 substance to which cobalt solution has been applied previous to the further 

 application to it of an oxidating flame ; for the colour imparted, blue, red, 



* Fluoride of calcium remains blue. 



t Oxide of zinc thus treated affords a beautiful peach-colour ; oxide of tin, after P. P., 

 a green. 



