ON CALCULUS 



147 



>recipitated powder, the solution will be acid. (The same 

 ling happens likewise with animal earth and fluor spar, if 

 icy be dissolved in the same acids.) If the solution be 



evaporated to dryness, it will at last take fire. If the 



>recipitate be heated only to a dull red heat in a close 

 :ucible, it grows black, smells like burnt alum, and 



jffervesces with acids. Before the blowpipe it changes into 



juicklime. 



(h) Neither the acid of sugar nor salt of sorrel precipitate 



bhis solution. The alkaline mixture (/) is also not pre- 



jipitated by these acids. 



SECTION IV. 



The calculus, when pounded and boiled with a solution of 

 ilkali of tartar, remains unchanged. But perfectly pure or 

 mstic alkali, such as shows not the least mark of aerial 

 acid, dissolves the calculus, even in the cold. The solution 

 is yellow, and tastes sweetish ; it is precipitated by all the 

 acids, even by the aerial. Lime-water is not precipitated by 

 this solution, but metallic solutions are decomposed. Iron is 

 precipitated brown ; copper, grey ; silver, black ; zinc, corrosive 

 sublimate, and lead, white. If there be a little superabundance 

 of alkali in the solution, it yields a smell of volatile alkali. 

 Dry volatile alkali has no effect upon the stone, but the 

 caustic prepared with quicklime dissolves it ; a pretty large 

 quantity, however, is required for this purpose. 



SECTION V. 



Lime-water likewise dissolves the stone by means 

 of digestion. 12 grs. of calculus require 4 oz. of 



