J90 GEOLOGICAL RECONNOISSANCE 



tate is considerable, it has to be dissolved in hydrochloric acid and precipi- 

 tated with carbonate of soda]. 



V. To the filtrate some hydrochloric acid is added, and heat applied until 

 the odors of chlorine and acetic acid have disappeared; the lime is then 

 precipitated with oxalate of ammonia, and from the filtrate the magnesia 

 with phosphate of soda. 



DOLOMITE, 



Containing : Insoluble silicates; carbonates of lime, and magnesia; sesqui- 

 oxide of iron with trace of manganese; alumina, potassa. 



I. The mineral is dissolved in hydrochloric acid, solution evaposated to 

 dryness^ residue treated with water acidified with hydrochloric acid, and 

 insoluble silicates and silica collected on filter. 



II. To the filtrate a little chlorine water is added, to oxidize the man- 

 ganese, then precipitated with ammonia; the precipitate, containing all 

 the iron, alumina, and manganese, and a little lime and magnesia, is re- 

 dissolved in hydrochloric acid and again treated as above. This precipi- 

 tate is free from the alkaline earths. It is dissolved in hydrochloric acid 

 and the solution divided into 2 equal portions: 



In the first portion iron plus alumina are determined by ammonia; 



In the second portion the iron alone is determined by chamseleon mineral. 



III. The two filtrates, and washings, are united, and about ^th of the 

 liquid used for the determination of lime by oxalate of ammonia, and that 

 of magnesia by phosphate of soda. 



IV. For the determination of the alkali a fresh portion of the mineral 

 is treated with repeated portions of boiling acetic acid; the filtrates are 

 united, evaporated, transferred to a platina capsule, and ignited until the 

 empyreumatic odor of decomposing acetic acid disappears; the residue is 

 exhausted with boiling water, the liquid mixed with some oxalic acid, 

 evaporated to dryness, ignited; the residue is again treated with boiling 

 water: the filtrate contains the potassa as carbonate; it is converted into 

 chloride, ignited and weighed. 



DETERMINATION OF NITRIC ACID. 



To ascertain the quantity of nitric acid in the nitre earths subjected to 

 analysis, I proceeded as follows: 



100 grammes of the earth are pulverized, and digested over the water- 

 bath with repeatedly renewed portions of distilled water until all the 

 soluble constituents of the earth are taken up by this liquid. The solution 



