tJ'aturt imi Fropirties of the Acid of Siherhn Rid Leai^ J^ 



»ided^ a little at a time, the oxide of Civer precipitated from its folution by lime water of 

 ty a cauftic alkali, and well waflied. 



The oxide of filver unites by preference with the muriatic acid, and forms with it a white 

 infoluble fait, which falls to the bottom of the fluid. But great care muft be taken not to 

 «dd too great a quantity of the oxide of filver, becaufe it will unite likewife with the acid of 

 the red lead, and form an infoluble combination, which will mix with the muriate of filver. 

 As foon, therefore, as it is obferved that the oxide of filver aflumes a purple red colour, it 

 is a fign that the muriatic acid is entirely faturated, and no more of the oxide muft be 

 added. It is better, however, to add too much than too little ; for, in this cafe, the only 

 danger Is that of lofing a fmall quantity of the acid of red lead ; whereas, in the other, the 

 inconvenience will be, that a portion of the muriatic acid will be left in combination with 

 ■flie metallic acid. When the acid of red lead, mixed with muriatic acid, is evaporated 

 fa) drynefs, a lilac-coloured powder is obtained, which becomes green by the conta£l of the 

 inr, and is a combination of the oxide of the new metal with the muriatic acid. 



SECTION V. 



^le Nature and Properties of the Acid of Red Lead. 



THE acid of red lead, prepared according to the foregoing inftru£lions, is of an orange- 

 Tcd colour, with a (harp metallic tafte. It is very foluble in water, and its folution evapo- 

 rated by a gentle heat, or fpontaneoufly by expofure to the air, cryftallizes in fmall long 

 prifms of a ruby-red colour. 



Experiment i . — Paper wetted with this acid, and expofed for feveral days to the fun's 

 light, aflumes a green colour, which does not change in obfcurity. 



Experiment 2. — A plate of iron, of tin, or moft of the other metals, Immerfed in the folu- 

 6.on. of this acid, caufes it to aflume the fame colour. 



Experiment 3. — Ether or alcohol, boiled for a few inftants with this fubftance, produces 

 the fame effeft. 



Experiment 4.— The muriatic acid, heated in a retort with this acid, whether foHd or in 

 folution, produces a lively effervefcence. Much oxygenated muriatic acid is afforded, and 

 the fluid aflumes a beautiful deep green colour. 



Experiment 5.— Thefe phenomena, which alfo take place when the ore of red lead is 

 idlflblved in the muriatic acid by means of heat, having led me to prefume that the acid of 

 fed lead, by virtue of the great quantity of oxygen it contains, and the flight adherence it 

 contracts with that principle, might favour the folution of gold in the muriatic acid, I put 

 fome leaves of that metal in a mixture of thefe two acids, and, by a flight ebullition, I ac- 

 tually obtained a complete folution of the gold. 



The colour of this folution was green ; it tinged the flcin purple ; and the folution of titt 

 recently prepared occafioned a very abundant precipitate of the fame colour. 



Experiment 6,— This acid, mixed with a folution of the hydro-fulphuret of pot-aih. Is pre- 

 cipitated in greenilh brown flocks. 



Experiment 7. — The aqueous fplwtjon of the tanning principle precipitates it in flocks o« 

 3 yeUowifli brown colour, 



2 E a pKperiment 



