Mineralogy of South America. 143 



The quantitative analysis was effected as follows : — 



100-37 grains of the nitrate dried at 212°. "The nitrate did not 

 contain any other than hygroscopic moisture •" it dissolved into 

 a colourless solution in cold water, and left 0'32 grain insoluble 

 red sand, equivalent to 0*31 per cent. The solution was divided 

 into three portions, respectively representing 50" 185, 25*092, 

 and 25*092 grains in weight of the original mineral. 



50*185 grains gave, upon addition of oxalate of ammonia, a 

 precipitate of oxalate of lime, which, upon incineration, yielded 

 0*22 carbonate of lime, equivalent to 0*23 per cent, of lime, or 

 representing 0*45 per cent, chloride of calcium. 



25*092 grains gave, when precipitated by nitrate of silver, 

 13*69 grains chloride of silver, equivalent to 13*41 per cent, 

 chlorine, from which, after deducting 0*22 as combined with 

 calcium, the percentage of chloride of sodium present was calcu- 

 lated at 21*63. 



25 09 grains, when precipitated by chloride of barium, afforded 

 0*42 grain sulphate of barytes, equivalent to 0*52 per cent, sul- 

 phuric acid, or 0*92 per cent, sulphate of soda. 



The nitrate of soda present was estimated by loss ; and the 

 analysis will therefore stand as follows : — 



Nitrate of soda . . . 76*69 



Sulphate of soda . . . 0*92 



Chloride of sodium . . 21*63 



Chloride of calcium . . 0*45 



Insoluble silica . . . 0*31 



10000 



The specimen represented by the above analysis must be re- 

 garded as not only far superior to the general average of what 

 would be regarded as native nitrate of the best quality, but 

 must be viewed more from a mineralogical than a technical point 

 of view. 



It was, however, considered interesting also to examine the 

 more massive nitratine for sake of comparison, and for this pur- 

 pose the following analysis was made. 



The specimen was taken from a virgin working about to be 

 commenced, situated on the slope of the hill overlooking the Sal 

 de Obispo, in the interior, to the west of the port of Pisagua, and 

 about 30 feet higher than the salt bottom of that dry plain or 

 former lagoon. 



The nitrate of soda here cropped out to the surface, barely 

 covered by a little sand and salt, and possessed a saccharine- 

 white appearance veined with brownish dirty-looking streaks ; 

 the quality was pronounced fine by the experienced workmen, 

 and the specific gravity taken in petroleum was found to be 2*21 



