Mil ture, and its Effects. 89 



iron had been dropped into it. This intestine 

 commotion is called effervescence. 



I shall now exhibit some instances of the mix- 

 ture of solids with fluids. In their union the 

 solid body is often divided into atoms so minute, 

 that they make with the fluids a homogeneous 

 liquor, and will remain dissolved as long as the 

 quality or quantity of the fluid is not altered. 



Thus Camphor thrown into spirit of 'vine 

 sinks at first ; but, dissolving and uniting by 

 degrees, the fluid remains transparent as be- 

 fore. 



Again Drop a piece of marble into muriatic 

 acid, and bubbles will arise, a violent effer- 

 vescence is produced, the marble is dissolved 

 into atoms so perfectly minute, that they be- 

 come invisible, and are equally mixed with the 

 fluid and diffused in it. This is an instance of 

 effervescence between a solid and a fluid; the 

 operation is called solution, and the fluid a solvent 

 or menstruum. In solution a solid must not only 

 be so mixed with the fluid, as to be equally dis- 

 persed and not to subside, but the mixture must 

 be perfectly transparent. In some mixtures, 

 though the matter is entirely mixed, yet for want 

 of transparency it is not called solution, but dif- 

 fusion (and in pharmacy an emulsion}. 



Saturation, I formerly observed, is used to 

 signify that some bodies are capable of being 

 united only in a certain proportion, and when a 

 menstruum or fluid has taken up exactly as much 



