72 TIN AND COPPER. 



46. MIXTURES OF PROTOXIDE OF MERCURY, 

 MINIUM, AND CINNABAR. 



By digesting with dilute nitric acid, the protoxide 

 of mercury is extracted, together with a portion of the 

 protoxide of lead, the remainder of the lead being left 

 behind in the form of brown binoxide, mixed with the 

 cinnabar. This residue is well washed upon a weighed 

 filter. 



From the solution, which must contain an excess of 

 nitric acid, the lead is precipitated by an excess of sul- 

 phuric acid, and a little alcohol. The mercury may 

 then be precipitated as protochloride by hydrochloric 

 acid and phosphorous acid. Before the separation of 

 the lead these last two reagents would have given 

 chloride of lead with the protochloride of mercury. 



The mixture of cinnabar and binoxide of lead is 

 treated, upon the filter, with a warm mixture of dilute 

 nitric acid and a little oxalic acid, which dissolves the 

 binoxide of lead, with evolution of carbonic acid. The 

 cinnabar is then washed, dried at 100, and weighed. 



The lead is precipitated from the solution by sul- 

 phuric acid, with addition of some alcohol. 



In order to analyze the cinnabar, it is dissolved (in 

 this case, together with the filter) in concentrated hydro- 

 chloric acid, with careful addition of chlorate of potassa ; 

 the sulphuric acid is then precipitated from the diluted 

 solution by chloride of barium, the filtrate concentrated, 

 and the mercury precipitated by protochloride of tin, 

 or, better, by phosphorous acid. 



47. TIN AND COPPER. 

 (Bronze, Gun-metal, Bell-metal.) 



I. The alloy, as finely divided as possible, is oxidized 

 with concentrated nitric acid, the greater excess of the 



