230 Dr. Marcet on an Aluminous Chalybeate Spring 



This precipitate, after being carefally separated, edulcorated, dried, 

 and ultimately heated to redness with wax in a platina crucible, 

 weighed exactly 14 grs. It appeared in the form of a red-brown 

 .magnetic powder.* 



6. Since therefore 50 grs. of crystallized green sulphat of iron, 

 gave 14 grs. of this oxyd, the 7,2 grs. of oxyd obtained from 

 50 grs. of residue, would represent 25,7 grs. of green sulphat of 

 iron; and 11,59 grs. of oxyd (which is the quantity contained 

 in an English pint of the water), would represent 41,4 grs, of that 

 salt. 



§ IX. Sulphat of A! amine . 



1. Fifty grains of residue f were boiled in two successive lixivia 

 -of ca-ustic potash (as in § VIII. 1), so as to take up all the alumlne 

 present ; the residue was separated and well washed, and the wash- 

 ings were added to the alkaline solution. The clear liquor had a 

 brownish colour, and on being tried with muriatic acid and prussiat 

 of potash, a blue tinge was produced, which appeared to have 

 Arisen from a few particles of oxyd of iron which were suspended 



* Thts result ^Th!ch was obtained in two cIiffi.Tcnt trials, with the variation of only 

 /3,1 gr. corresponds exactly with the proportions given by Mr. Kirwan in his treatise 

 on mineral waters (table iv.), in which 28 grs. is the quantity of oxyd stated to exist 

 in 100 grs. of green sulphat. But in order to establish the perfect coincidence of these 

 rcs-nlts, it would be necessary to know the process which Mr. Kirwan followed. Tlte 

 iron in his experiment, is stated to have been obtained iii the state of black oxyd. 



■(- These fifty grains had been previously boiled in neutral carbonat of ammonia, in 

 order to separate the magnesia as will be detailed hereafter. The previous intcrven. 

 tion of a carbonated alkali renders the subsequent application of caustic potash for the 

 separation of the alumine, more unexceptionable, as a solution of caustic potash might 

 rcdissolvc a small portion of the liuie, if it were not previously carbonated. 



