Frm S-tRONT'lJN. i9 



tin^ulfh a candle by means of carbonic acid gas, as it ilTues 

 from a brifkly efFervefcing folution of the fpar in muriatic acid. 

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

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

 I {hall enumerate them In the order of their power : Tartrite, 

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

 borate ; the efFeft of the two laft is extremely feeble *. 



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

 dity is abfolutely requifue to enable thefe fubflances 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 brmg 

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

 not afFea the flame ; moiften it, and inftantly you reflore its 

 former power. This holds true with regard to all the reft ; fo 

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

 their compofition will not affba 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 refped to the acetite, 

 though in a cryftalline form. 



47. All the combinations of Strontites with dlff"erent acids, 

 excepting the carbonate, are decompofed by the three alkalis in 

 their ordinary effbrvefcent ftate, by virtue, in part, of a dou- 

 ble eledive attradion. When a folution of carbonate of po- 

 tafs, for example, is dropped into the muriate, at firft a tranf- 

 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 effervefcence 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 Edin- 

 burgh. 



