146 ESSAY IX. 



SECTION III. 



(a) The diluted nitrous acid, or aquafortis, had some 

 effect upon the calculus, even in the cold. On the application 

 of heat, an effervescence ensued, and red vapours arose ; the 

 calculus was entirely dissolved. If the experiment be made 

 in a retort, and lime-water be put into the receiver, it will be 

 precipitated. 



(&) This solution is acid, though the menstruum be boiled 

 with a superabundant quantity of powder, so that there may 

 remain a portion of it undissolved. 



(c) This yellow solution produces deep red spots upon the 

 skin in half an hour after it is applied. If the saturated 

 solution be a little more evaporated, it assumes of itself a 

 blood-red colour, which, however, disappears on dropping in 

 a single drop of nitrous acid. 



(d) A solution of ponderous earth in muriatic acid 

 precipitates nothing from this solution. 



(e) Metallic solutions are not sensibly changed by this 

 solution. 



(/) It is not precipitated by alkalies, but only grows a 

 little yellower when the alkali is superabundant, and then 

 this mixture, in a strong digesting heat, likewise assumes a 

 rose colour, and produces spots of the same colour very 

 quickly, and without any sense of burning upon the skin. 

 This mixture likewise precipitates metals of different colours : 

 vitriol of iron, black ; vitriol of copper, green ; silver, grey ; 

 corrosive sublimate, zinc, and lead, white. 



(g) Lime-water decomposes this solution, and precipitates 

 a white powder from it, which I have edulcorated and dried. 

 This precipitate is soluble in muriatic and nitrous acids 

 without any effervescence. Though there be an excess of the 



