!<)• Neiv Metallic Aeid in Sthei'lan Rtd Ltatt, 



abforb, in order to combine with acids, li parts of oxygen, the 57,1 of metallic lead muft: 

 contain in the red lead 6,86 of this principle 5 which leaves the weight of the mineralifing 

 acid 36,4. 



Experiment 6. —To verify by fynthefis the prdportion of principles found by analyfis in. 

 the red lead, I diflblved 50 grains, ov about a>654 grammes, of metallic lead in ni^r^c 

 acid, which was divided into two equal parts- One of thefe was completely precipitated. 

 by the requifite quantity of the combination of the acid of red lead with potafh ; and I 

 obtained 43 grains, or about 2,285 grammes, of red lead as fine as the native mineral 



The other portion of the nitrate of lead, precipitated by cauftic potafti, afforded 28 grains 

 of the white oxide of lead. So that by this fynthefis ido parts of red lead would be com- 

 pofed of 65,12 of oxide of lead, and 34,88 of acid. It gives, therefore, a difference pf 

 1,72 lefs of acid than waft deduced by the analyfis, jn the mineraliling acid of the red lead ^ 

 a difference which (hews as great a degree of accuracy as the chemical methods can afford^ 



SECTION IV. 



Tie fecmd Procefs for decompoftng the Red Lead Ore. 



ANOTHER method, of which the execution is no lefs eafy than the foregoing, confiffs 

 in pouring 100 parts of muriatic acid diluted with the fame quantity of water upon leO' 

 parts of the red lead ore in powder, and occafionally agitating the mixtU/re. 



In this cafe the muriatic acid combines with the oxide of lead, and forms an infoluble fait,, 

 which falls down, while the acid of the red lead remains diffolved in the water which was 

 before mixed with the muriatic acid. The fluid affumes a colour perfedlly refembling that 

 of the red lead before it was pulverifed. As foon as it is perceived that the muriatic acid 

 exerts no' further action on the red lead, and the precipitated muriate of lead ftill contain?, 

 fome red particles, the fupernatant liquor is decanted, and a new quantity of muriatic acid, 

 <Dne third or one fourth of the original quantity, and diluted in the fame manner, is poured 

 on the refidue. 



The decompofition being complete, the fecond folutlon is decanted, and added to the 

 firft ; the refidue, is walhed with a fmall quantity of cold water, which is alfo added to the- 

 folutions before decanted off. 



In this procefs the operator finds himfelf under the necedlty of obtaining his acid of red 

 lead mixed with a certain quantity of muriatic acid, or of leaving a portion of the red lead 

 jmdecompofed. 



In faft, if, according to the known proportions of the component parts, no more of thfc 

 muriatic acid were to be added than is neceffary for the faturation of the oxide, part of th& 

 red lead would efcape decompofition ; for it appears that the acid of the red lead, at the- 

 time of its feparation, unites witli a portion of the muriatic acid, which feems neceffary 

 for its more ready folution in the water. 



Of thefe two inevitable inconveniences I have therefore preferred that which leaves % 

 faiall portion of the muriatic acid in the acid of red lead, becaufe it is eafy to feparate it. 



For this purpofe the acid of the red lead, contaminated with muriatic acid, is to be di- 

 luted with a fmall quantity of water, and left at reft in a cool place for feveral days, in 

 order that the fmall portion of muriate of lead which it may contain fhould cryftallize and 



fall down. The fluid is then to be filtered or drawn off by a fyphon ; and to this muft be. 



added. 



