ON CALCULUS VESIC^ 153 



dryness, and the dry mass calcined to whiteness, a 

 calcareous powder is thus likewise obtained. 



As pure vitriolic acid contains no phlogistic matter, 

 I expected that it would, in the present case, immediately 

 show the presence of lime, a circumstance which really 

 happened. I dropped some pure concentrated vitriolic 

 acid into a solution of calculus in nitrous acid, and found 

 that, when the solution was saturated, some small crystals 

 immediately separated from it. They proved, on examina- 

 tion, to be gypsum ; and, after being dissolved in distilled 

 water, they were precipitated by the acid of sugar. When 

 the solution of the calculus was very much diluted, there 

 appeared no change in the beginning; but after a little 

 evaporation the above-mentioned crystals began to appear. 

 Some calculi of the bladder or kidneys at least certainly 

 contain lime, but seldom more than one-half in a hundred 

 parts, or one in two hundred parts. 



Concentrated vitriolic acid dissolves the calculus, when 

 assisted by heat, with effervescence; the solution is dark 

 brown. If a little water be afterwards added, there seems 

 to take place a kind of coagulation ; but on adding more 

 water all grows clear again, and assumes a yellowish brown 

 colour. 



The muriatic acid seems to have no effect upon it. I 

 am, however, in doubt whether it will not extract at least 

 a portion of the calcareous earth, and shall for this 

 reason make some further experiments to determine this 

 point. 



The red colour which the solution of the calculus in 

 aquafortis may be made to assume is remarkable. A 

 saturated solution discovers no smell of nitrous acid, and, 

 if evaporated by itself in a large open vessel, the liquor 

 assumes at last a deep-red colour, and it hardly contains 



