Examination of the Purity e/Medicities, life, ffpr 



lead become precipitated in the form of a more or lefs dark-coloured powder, which is to 

 be feparated by the filter, and wafljed with diftilled water. 



Tb analyle this precipitate, It is firft treated, with pure ammoniac, which foon acquires . 



a blue colour If copper be prefent. The blue fupernatant fluid is to be feparated, the 



remainder wafhed in diftilled Wat«r, and then diflblved in pure muriatic acid. 



In order to afcertaln the prefence of lead, the foregoing folution is mixed with an equal 

 quantity of wat-er im,pregnated with fulphuratcd hydrogen gas; and if a dark brown or 

 black precipitate enfues, it is a fure fign that lead is prefent. 



Iron that may happen to be in folution is exhibited by the admixture of a few drops of 

 pure prufTiate of potaQi or tin£lure of gall-nuts, which in the fitrft cafe will produce a blucj. 

 and in the fecond a black precipitate. 



Sulphate of potafli, or th« vegetable alkali, united to fulphuric acid is more difficult to 

 difcover, as for this purpofe a certain quantity of the acid is to be perfeftly faturatcd wkL 

 carbonate of potafh, or carbonate of ammoniac ; to this folution a little tartareous acid is 

 to be added, which by its fuperior aflSnrty will decompofe the vitriolated tartar, and indi- 

 cate the vegetable alkali under the form of tartarite of potafh feparated from the fluid. 

 If the quantity in the acid be not very fmall, as is feldom the cafe, it may alfo be dif*- 

 covered by the admixture of ftrong ardent fpirit j for by this means a quantity of ful- 

 phate of potafh, wHl be feparated in the form of a white powdery precipitate. 



The fpeci fie gravity of fulphuric acid, according to our pharmacopoeia, fliould be to 

 that of diftilled water as 185 to 100. 



Ir is void of fmell — perfe£Hy colourlefs — and boils at 546' of Fahrenheit's thermometer. 



Equal parts of vitriolic acid and water, h»ftlly mixed together, flwuW produce a.hc^''. 

 nearly equal to that of boiling water. 



Nitrous Acid*. 



THE nitrous acid of commerce (or double aqua fortis aa it Is commoniy called) always 

 contains either fulphuric or muriatic acid, and often both. 



The vitriolic acid may be difcovered by the addition of a few drops of a folution of 

 nitrate of barytes, or acetite of lead, which fort^ infolnble compounds and fall down. The 

 muriatic acid Is manlfefted by thcaddition of a folution of nitrate o;f fiiytfr. In 6hi$ cafe 

 muriate of filver is formed and precipitated. 



Its fpecific gravity ftiould be to that of diftilled water, as 155 to 100. 

 . If it is of an orange yellow colour, and emits a vaft quantity of elaftic fluid, known by 

 the name of nitrous gas, which forms yellow fumes In our atmofphere. Mixed with water, 

 it develops a confiderable degree of heat f . 



*vThe infiruflion for preparing nitrous acid according to our phartracopceia is erroneous, ss the proportion of- 

 fulphuric acid prcl'crilkd is much too fmall,: it confequentiy leaves a confiderable quantity of nitrate of potafli, 

 bthind undecompofed. A. 



, f Pure nitrous acid is deprived of a portion of nitrous gas by the application of heat.. It is then coiourlefs, 

 anJ conftitutes nitric acid. Expofure of nitric acid w light expels oxygen, and leaves the acid with that re..- 

 .dundancy of azote which conftitutes the nitroUs or yellow acid, Nitric acid muft therefore he kept in the dark,, . 

 •r elfe in bottles quite full. N. 



Muriaiie.- 



