ITfW Metallic Acid in Siierian Red Lead, 08* 



■^ . :■ - The firjl Method. 



Experiment I. —^100 parts of this mineral reduced to a fine powder were mixed with 

 300 parts of faturated carbonate of potafli ; and this mixture, together with about 4000 

 parts of water, was boiled for an hour, I obferved that,- 1. as foon as the re-a£lion of the 

 principles began, a ftrong efFervefcence was produced, which lafted for a long time ; 2. the 

 orange colour of the lead became a briclcduft red ; 3. at a certain period the whole ap- 

 peared to be in folution ; 4. in proportion as. the efFervefcence proceeded, a coarfe powder 

 of a dirty yellow colour was thrown down ; 5, and laftly, the fluid affiimed a very fine 

 golden yellow colour. 



As foon as the effervefcence had entirely ccafed, and the re-adlion appeared to have tcr- 

 '^minated, the fluid was filtered, and the metallic powder collcifled. After wafhing and 

 ■;drying, it was found to weigh only 78 parts ; the potafh had therefore taken up 22 

 parts.; .'.^.j ^Lo.'^-.u ..._ 



Experiment 2. — Upon the 78 parts laft mentioned I poured nitric acid diluted with 

 12 parts of water. A ftrong effervefcence followed ; the greateft part of the matter was 

 diflblved ; the fluid did not acquire any colour ; and the undi^blved refidue confifted of a 

 frnall quantity of lemon-colpured powder. I feparatcd the fluid part from the refidue by 

 means of a fyphon, waftied the remaining powder feVeral times, and added the waters to 

 the former folvent. The refidue, when dried, weighed ottly 14 parts ; whence it foUowsj 

 that the nitric afcid had diflblved 64 parts. "' '-^■' " ' <" •' ; 



Experiment 3.— I again mixed thefe 14 parts with 42 parts of carbonate of potafli, and 

 the requifite quantity of water. Thefe being treated as before, afibrded the fame pheno'- 

 mena. After filtration of the liquid, it was added to the firft folution. The refidue, waflied 

 and dried, weighed i parts. It was red lead, and was iiegle£ted. 



Experiment 4. — ^The two nitric folutions put togethei' and evaporated afibrded 92 parts 

 of nitrate of lead, cryftallifed in oflahedrons, pcrfeftly white and tranfparent. : 



Thefe 92 parts of nitrate of lead diftblved in water were precipitated by a folution of 

 fulphate of foda. The produd was 81 parts of fulphate of lead, which anfwerto 56,68 of 

 metallic lead. 



£*/im«^«^ 5 .—Tne alkaline folutions, which were of an orange-yellow colour, were 

 put together. In the courfe of feveral days they depofited two parts of a yellow powdet 

 which did riot contain lead. Thefe folutions, evaporated till a pellicle was formed on the 

 furface, afforded yellow cryftals by coolfng, among which was carbonate of potafli not 

 ■decompofed. ... 



Thefe cryftals were diflblved in water, and the folution, together with the mother water, ' 

 was mixed with the weak nitric acid till the carbonate of potafli was faturated. The fluid 

 Jiad then a very deep orange-red colour. "When mixed with a folution of muriate of tiiji 

 recently prepared, it firft afliimed a brown colour, which afterwards became greenifli. 

 When mixed with a folution of the nitrate pf lead, ' there was an immediate regeneratiott 

 of the red lead. And, laftly, by fpontaneous evaporation, it afforded cryftals of a ruby re^ 

 colour, mlxe^. with cryftals of nitrate of potafli. 



Ninety-eight paris of this mineral, decompofed as h^s been here related, having aflx)rded ^ 

 Sj'parts of fulpl)ate".pf'leW, ic6 parts' 'Would have afforded 82,65, which are equivalent to 

 ^j7,i of metallic, lead. " No.wi ^{nit'ting, 'aS Is proved by' experiment, that 100 parts of lead 

 : ■V:oj-.il.-13EcM79$.'^'' " •' '•• ' • "'■ -^E- •' - •• -• ■ ■ - ■ ablbrb^ 



