734 GEOLOGY a:>'d mixing industry or leadville. 



No. i8 — Sulpbate of lead is reduced by carbon to the state of sulphide: PbO, 

 S03+C,=PbS+2C02 (Gay-Lussac),' and also by carbonic oxide (Rodwell).^ The 

 sulphide of lead of the mattes is produced partly bythese reactions. 



No. 19. — Sulphate of lead is decompo.scd by lime with formation of sulpbate of 

 lime and oxide of lead; sulphate of lime has been pointed out in the analyses of some 

 furnace products. 



No. 20. Reactions of sulphide of lead — Sulphide of lead is somewhat volatile; it is 

 sublimated at high temperatures (Berthier, Percy). This sublimated galena in fine 

 distinct irisated crystals is one of the constituents of normal shaft accretions. 



No. 21 — Sulphide and oxide of lead react upon each other with formation of 

 metallic lead and sulphurous acid (see reaction No. 10). 



No. 22 — Suljihide of lead antl metallic lead combine together and form subsul- 

 phides and alloys. The analyses of bullion and skimmings prove this reaction. More- 

 over, the metallurgical collection of the Survey contains specimens of alloys highly 

 charged with sulphide of lead. 



No. 23 — Sulphideof lead is reduced by zinc: PbS+Zn=Pb+ZnS (Percy-Smith). 

 The sulphide of zinc found in normal accretions and also in lead fumes is certainly 

 deposited in virtue of this i-eaction. 



No. 24 — Sulphide of lead and sulphate of lead react ujion each other with forma- 

 tion of metallic lead and sulphurous acid: PbS-f PbU,S(-'3=2Pb+2S02 (Berthier, 

 Percy). 



No. 25 — Sulphide of lead and iron produce one of the most important reactions 

 of the blast furnace; lead is completely reduced to the metallic state and sulphide of 

 iron isforraed: PbS+Fe=Pb-|-FeS (Berthier). Mostof the sulphide of iron in mattes 

 is produced in this way. 



No. 26 — Sulphide of lead and oxide of carbon act slightly upon each other with 

 formation of sulphide of carbon (Podwell).^ In all probability some of the silica found 

 in that portion of the fumes which escapes in the air is volatilized in the state of sul- 

 ])hide of silicium by the sulphide of carbon thus produced. 



No. 27. — Sulphide of lead mixed with lime. ai.d carbon is partly reduced with for- 

 mation of sulphide of calcium aud carbonic oxide: 2PbS-|-CaO+C = Pb+PbS,CaS-!- 

 CO (Berthier). This important reaction, which undoubtedly takes place in the zone of 

 agglomeration of the furnace, accounts for the sulphide of calcium iu the slags. 



No. 28 — Sulphide of lead, heated wilh oxide of iron and carbon, produces metal- 

 lic lead aud .sulphideof iron: 4PbS+2Fe.,03+3C=4Pb+4FeS+3C02.^ This reaction 

 is interesting as indicative of what actually takes place in the furnace. 



No. 29 — Sulphide of lead and basic sdicate of protoxide of iron react upon each 

 other with formation of metallic lend, and iron and lead matte: 2(3Fe0, Si03) + 5PbS= 

 2(2FeO, Si03)-f2(PbS, FeS)-fSO>+Pb3 (Percy Cloud). This important reaction is 

 illustrated by the specimens of hearth accretions or slag mattes in the collection of 

 the Survey. 



> Ann. (le Chini. et tie Phys., 1636, 73, p. 435. 



-Journal of ihe Chemical Society, new series, 1863, p. 42. 



'Journal of the Chem. Soc, antea cit., p. 48. 



■•Jordan, Ertlmann's Journal, 16'.?1, 11, p. 3?4. 



