Dr T. THOMSON'S Analysis of some Minerals. 451 



parate the silica. The silica, after edulcoration, drying, and igni- 

 tion, weighed 2.96 grains. It was a fine white powder, and was 

 perfectly pure. 



The muriatic solution, thus freed from silica, was mixed with 

 caustic ammonia slightly in excess ; a greyish-brown precipitate 

 fell, weighing, after ignition, 0.58 grain. By solution in muria- 

 tic acid, and mixing the solution with caustic potash in conside- 

 rable excess, it was resolved into 



Peroxide of iron, . . . 0.185 

 Alumina, 0.395 



.580 



Thus, from the 4 grains of the siliceous-looking matter, se- 

 parated from the hydrolite, when it was treated with carbonate 

 of barytes and muriatic acid, were obtained, 



Pure silica, 2.96 



Peroxide of iron, . . . 0.155 

 Alumina, 0.395 



3.54 

 Loss, 0.46 



4.00 



This loss could have been owing to nothing but the pre- 

 sence of a little potash in the siliceous matter (the liquid was 

 carefully examined, but nothing found), which I could not ob- 

 tain, because I had fused the 4 grains of siliceous matter with 

 carbonate of soda. 



If we now add together all the constituents, we shall find 

 that 5.8 grains of anhydrous hydrolite are composed of 



VOL. XI. PART II. 3 L 



