Frdm Sf RON TUN. ig 



tinguifh a candle by means of carbonic acid gas, as it ilTues 

 from a brlfkly effervefcing folution of the fpar in muriatic acid. 

 After the nitrate, comes Strontites in cryftals ; the acetite holds 

 the next place. Thofe that follow give but a faint tinge of red. 

 I fhall enumerate them in the order of their power : Tartrite, 

 fulphate, oxalate, fluate, arfenicate, carbonate, phofphate and 

 borate ; the effect of the two lafl is extremely feeble *. 



46. It is worthy of remark, that a certain portion of humi- 

 dity is abfolutely requifite to enable thefe fubftances to alter the 

 hue of the flame. By way of illuftration, dry by a gentle heat 

 the mod powerful of them all, the muriate, and by that bring 

 it to the ftate of a dry white powder. In this condition it will 

 not affedl the flame j moiften it, and inftantly you reftore its 

 former poM'^er. This holds true with regard to all the refl: ; fo 

 much fo indeed, that thofe which have not much moifture in 

 their compofition will not affe<5t the flame without an addition 

 of humidity. This is the cafe with the fulphate, tartrite, oxa- 

 late, phofphate, arfenicate, borate, fluate, carbonate and cal- 

 cined fpar. Nay, it is even true with refpedl to the acetite, 

 though in a cryftalline form, 



47. All the combinations of Strontites with different acids, 

 excepting the carbonate, are decompofed by the three alkalis in 

 their ordinary efl^ervefcent (late, by virtue, in part, of a dou- 

 ble eledlive attracflion. When a folution of carbonate of po- 

 tafs, for example, is dropped into the muriate, at firfl: a trans- 

 parent gelatinous precipitate is formed, which, upon agitation, 

 after further additions of alkali, acquires a white curdy appear- 

 ance. Similar phenomena accompany the precipitations by the 

 carbonates of foda and ammoniac ; no eflfervefcence attends any 

 of them. The precipitate, when dried, proves to be a white 



C 2 fubtle 



* The beautiful experiment with the muriate was firft mentioned to me in the 

 1787, by an ingenious gentleman, Mr Ash, who was then ftudying phyfic at iLdin- 

 burgh. 



