350 Examination of Ores of Iron. 



Character. Its powder is nearly black when powdered 

 without its matrix, but with it, grey ; slightly magnetic ; spe- 

 cific gravity 3,58. 



Its gangue granite. 



This ore was treated by the same pi-ocess as No. 1, and 

 yielded of granitic rock sixty, black oxide of iron forty, and 

 a trace of manganese, or 24.88 of pure iron in the hundred ; 

 this ore is said to work very readily, probably owing to the 

 large quantity of felspar in its gangue. 



No. 3. Iron ore from Crown Point, Essex County, New- 

 York. 



Character. Not magnetic ; specific gravity 3.9C ; pow- 

 der of a purple brown. 



Analysis. ( 1 .) A piece of this ore was coarsely powdered ; 

 in order to examine the earthy residuum with the microscope, 

 after it had been submitted to muriatic acid. 



(2.) One hundred grains of the powder was boiled in muri- 

 atic acid for half an hour, the solution decanted and more 

 acid added until it ceased to act on the mineral ; the solu- 

 tions were then put together, and the residuum washed ; the 

 washings added to the solution, the residuum then weighed 

 17.50 grains. (See 6.) 



(3.) To the muriatic acid solutions and washings, pure 

 potassawas added in excess, to throw down the oxide of iron. 

 The oxide was then dried and ignited with wax. Jt then 

 weighed about seventy-two grains ; when first precipitated it 

 weighed eighty-three, hence it will appear that this ore con- 

 tains more oxygen than ores No. 1. and 2. 



(4.) The muriate of potassa, which was found in adding the 

 potassa to the muriatic solution of iron, was then examined 

 in the following manner : first, some pure water of ammonia 

 was dropt into a portion of it, to precipitate the alumine if any 

 was present; it had no effect on the liquid; next the solu- 

 tion of oxalic acid was thrown into another portion of it, to 

 determine if all the iron had been precipitated, this likewise 

 had no effect. 



