1 882. 31 Trans. N. V. Ac. Set. 



silica, etc., and calling what remains red oxide, we would have the 

 approximate mineralogical composition of Sample " D ": 



Franklinite 5 ^ • 5 ^ 



Red Oxide of Zinc 6.40 



Rhodonite 11.13 



Willemite 20.23 



Carbonate of Many: n-se 1.24 



Limestone ^-7^ 



99.27 

 The next trial made was to determine some solvent which would dis- 

 solve the red oxide of zinc, and practically leave the other mineral con- 

 stituents, with the exception of the limestone, unacted on. 



The experiments made by Prof. H. Carrington Bolton, of Trinity 

 College, with organic acids, upon minerals, suggested to me the use of 

 an organic acid for the quantitative estimation of the red oxide. Citric 

 acid was first employed, but without satisfactory results ; and, after 

 several experiments, acetic acid was adopted as the best solvent ob- 

 tainable. 



The first step was to determine the solubility of Franklinite, Zincite, 

 Willemite, Rhodonite, etc., in acetic acid, and a number of experiments 

 were made with this object, the results being as follows : 



Solubility of Franklinite. 



Specimen. Locality. Amount Dissolved. 



No. I Franklinite (analyzed) 5 . 42 per cent. 



No. 2 Mine Hill • 2.63 



No. 3 Mine Hill 1.45 



No. 4 Crystals 0.57 " 



Average 2.52 " 



Time i hr. 30 min. 50 per cent, acid ; 50 per cent, water. 



Solubility of Red Oxide. 



Dark Red — Entirely soluble. 



Light Red — Slight residue reacting for Manganese. 



Solubility of Rhodonite. 



Specimen. Locality. Amount Dissolved. 



No. I Mine Hill 1.66 per cent. 



No. 2 Sterling 2.33 



No. 3 Franklin i .03 " 



No. 4 Mine Hill 2.18 



Average i .80 " 



Time i hr. 30 min. 50 per cent, acid ; 50 per cent, water. 



