20 ESSAYS AND 03SERVATia:^3 



eflPervefcence is aver, add a little more* 

 Kepeat this addition at proper intervals- 

 till no more effervefcence enfues. Then 

 throw the whole, with an equal or 

 greater proportion of water, into a filter 

 of grey paper, whole weighc is known. 

 When all the fluid parts have paffed 

 through, fill up the filter, again and again, 

 with warm water. By this means, the 

 diflTolved particles of calcarious earth, 

 adhering to tlte relidue, or entangled in 

 the pores of the paper, will be wafhed 

 awav, and nothing but what is really 

 tmfolable will remain in the filter. 

 This reftduum with the filter muft 

 be compleatly dried and weighed. 

 Then, the dif&rence betwixt its weight, 



and 



Tsntr.pe, the vrtrioHc excepted. For, tho' this acid ef. 

 fervefces violently with all marles, it does not diflblve' 

 their calciiriou^ earths; it only forms with them a whi- 

 tifh cont^uhim, which will not pafs thro* the filter. 



Is any trials that I have hitherto made with the ve- 

 getable acid, 1 have not been able by its means to estraff 

 all the cakarious earth contained in any marie. For,' 

 after the ufual filtration, the r^i/KK»j alwayse^ervefccd 

 »iolectly with the nJneral acids. 



