150 Intelligence and Miscella?ieous Articles. 



deposit of alumina and peroxide of iron was redissolved on the filter 

 by dilute hydrochloric acid. 



The solution was supersaturated with soda, which redissolved the 

 alumina, and left the peroxide of iron with a small quantity of lime 

 and magnesia, which the alumina had taken down with it. These 

 matters were redissolved in hydrochloric acid, and the oxide of iron 

 precipitated by ammonia, the filtered liquor being added to that 

 which contained the greater part of the lime and magnesia. 



The alkaline solution of alumina was decomposed by hydrochloric 

 acid, and this last separated by hydrosulphate of ammonia ; the per- 

 oxide of iron was dried and weighed ; it dissolved totally in boiling 

 hydrochloric acid. 



Lastly, the lime and magnesia were successively precipitated by 

 oxalate and phosphate of ammonia ; the ammoniaco-magnesian 

 phosphate was washed with slightly ammoniacal water. 



B. The decomposition of the mineral by means of hydrofluoric 

 acid, admitted readily of ascertaining the quantity of alkalies which 

 it contained. The operation was performed in a platina crucible, 

 and the solution evaporated to dryness with sulphuric acid"; the 

 residue was treated \v\\h water, the solution was filtered, the oxide 

 of iron and alumina separated by ammonia, and the lime then thrown 

 down by oxalate of ammonia. 



The liquor filtered after the separation of the lime was evaporated 

 to dryness, and the residue, heated to redness, consisted of alkaline 

 sulphates, mixed with sulphate of magnesia ; the sulphates were 

 dissolved in water and precipitated by acetate of barytes ; the solu- 

 tion was filtered, evaporated to dryness, and calcined to decompose 

 the acetates and convert them into carbonates ; these were treated 

 with water ; the alkaline carbonates dissolved, and the magnesia 

 remained insoluble with the carbonate of barytes. 



The alkaline carbonates were converted into chlorides and weighed, 

 the potash precipitated by chloride of platina. The magnesia was 

 separated by sulphuric acid from the carbonate of barytes, with which 

 it was mixed, and estimated in the state of sulphate. 



C. The employment of excess of boiling sulphuric acid and eva- 

 poration to dryness, is a very simple method of analysing minerals of 

 this description. The substance decomposed by this method was 

 treated with water ; the deposit separated by filtration, and which 

 consisted of silica, readily dissolved in excess of caustic soda, except 

 a minute quantity of sand, which did not amount to more than 0'0140 

 of the weight of the substance submitted to analysis. The alkaline 

 liquid, saturated by an acid, gave pure silica, which was separated by 

 the usual processes, after the evaporation to dryness had been twice 

 repeated. 



The mean of four analyses performed by M. Salvetat (I.), and of 

 three by M. Daraour (II.), gave the following results; — 



