i882. 



33 



Trans. N. V. Ac. Set. 



Solution C. 

 Boil with KClOa.to oxidize sulphur. 

 Neutralize carefully and precipitate 

 Manganese with Br water as usual. 

 Filter and wash, diss, in HCl, and 

 re-precipitate with NaQCOs. 

 Ignite and weigh Mn304. 



Precipitate C. 

 Wash with HaS water, diss, in 

 HCl, oxidize sulphur, re-precipitate 

 with NasCOs. Dry, ignite and 

 weigh the ZnO. 



Results. -1st. Residue insoluble in acetic acid. 

 2d, Silica in acetic acid solution. 

 3d. ZnO dissolved by acetic acid. 

 4th. MnOo dissolved by acetic acid. 

 Undetermined ; CaO and MgO dissolved. 



Taking into consideration the previous determinations of the solu- 

 bilities of the Silicates of Zinc and Manganese, etc., we have the fol- 

 lowing data : 



Ratio of Solubilities. — 29.32 (solubility of Willemite) is to 1.80 (solu- 

 bility of Rhodonite) as 16.5 is to 1. 



Ratio of Silica in these minerals (Dana), 27 to 46. Occurrence of 

 these minerals by supposition in these ores, i to i. Multiplying these 

 ratios together we have 445.5 to 46. Hence, approximately 90.64 per 

 cent, of the silica iti solution will be due to the Willemite, and 9.36 

 per cent, to the Rhodonite — say 9-10 and i-io. Applying this method 

 and adopting this basis of calculation, I obtained the following results 

 from a series of analyses made on ten different samples : 



Residue 



Silica 



Oxide Zinc 



Oxide Manganese 



Oxide Zinc for Silica 



Oxide Zinc for Red Oxide 

 Red Oxide 



80.86 

 1. 71 



11.63 

 2.71 



415 

 7.48 



7-79 



Residue 



Silica 



Oxide Zinc 



Oxide Manganese 



Oxide Zinc for Silica 



Oxide Zinc for RedOxide 

 Red Oxide 



80.22 



2-34 

 12.56 

 3-76 

 568 

 6.88 

 7.16 



74.76 

 2.74 



"•59 

 3-29 

 6.65 



494 

 514 



Average 



78 042 

 2.227 



10.778 

 3-185 

 5-407 

 5-370 

 5-593 



