1 1 8 PrectpiiaU formtd hy mixing Murialt of Lime, ?S*<r. 



fimply fulphurated, and thefe will then be two fpecies of minerals very different In theif 

 nature j the one diflblves in the fulphuric aijd muriatic acids without effer'vefcence, and 

 the other, on the contrary, affords a greater or lefs quantity of fulphurated hidrogen gas. 



Mercury, in a metallic (late, does not very intimately combine with fulphur ; ethiops 

 mineral appears to be rather a mixture than a real combination ; but when this oxided 

 metal is combined with fulphur, as in cinnabar, for example, it adheres f^ ftrongly, that 

 no fubftance is capable of direftly decompofing it } and it is only by altering one or the 

 other of thefe principles that their feparation can be effefted, or rather it is neceflary 

 to burn the fulphur or difoxide the mercury, cinnabar owes its fine red colour only to the 

 great quantity of oxigen which the mercury contains. 



VIL 



On the Precipitate formed by mixing Muriate of Lime and Muriate of Magnefta. By 



W. Lambe, M.J. 



To Mr. NICHOLSON. 

 S I R, 



H. 



-AVING difcovered, what I conceive to be, the true explanation of the appearance 

 of a precipitate by mixing the muriate of lime and magnefia, I take leave to communicate 

 it to you. All the accounts I have met with on this fubjefl are erroneous ; and that offered 

 by the celebrated Berthollet is as much fo as any (Journal, IV. 67). To refute it, I need 

 only mention a fingle fadl. Let the carbonate ofl magnefia, before diffolving it in the 

 muriatic acid, be thoroughly deprived of its carbonic acid by heat, and then there will 

 be no precipitation by mixing the two falts. To the carbonic acid, then, is this ap- 

 pearance to be attributed, of which the carbonate of magnefia cannot be wholly deprived by 

 the addition of fo much muriatic acid as will produce an apparent faturation. 



Diffolve fome common magnefia in a folution of carbonic acid in diftilled water. ' To 

 the clear folution add a little muriate of lime, and a precipitate is immediately formed, 

 entirely fimilar, I believe, to that in queftion. If the liquor be examined after fome days, 

 carbonate of lime is found dlffolved in it, inftead of carbonate of magnefia. It feems, 

 then, that thefe precipitates are formed by an interchange of principles between carbonate 

 of magnefia and muriate of lime, and confift of carbonate of lime and muriate of magnefia. 

 The liquor, by evaporation, depofits a cryftalline matter, which effervefces with acid, and 

 probably is compofed of the fame falts in different proportions, 



Laftly, put fome of the precipitate in the nitric or muriatic acids. It diffolves flowly, 



with a gradual extrication of air bubbles, and adding acid enough, it may be wholly con- 



4 ~ verted 



