1820.] M. Stromeyer on Polyhalite. 437 



(D.) 



Lastly, in order that the real quantity of sulphuric acid con- 

 tained in the fossil might be accurately ascertanied from direct 

 experiments, I made an analysis in the following manner : 



a 7-'?47 o-rms. of polyhalite being reduced into a very hne 

 powder were boiled up with 200 grms. of pure water, which 

 process was repeated with the same quantity of water until no 

 more of the residuum woidd dissolve, or excite a brackish 



flavour. . , 1 •, J • i. 



b The liquid obtained by the fossil, being thus boiled in water 

 and afterwards precipitated by acetate of barytes, produced 

 6-638 grms. of sulphate of barytes, which, when ignited, were 

 reduced to 6-539 grms. 



c. After the separation of the sulphuric acid, I evaporated the 

 acetic solution, exposed the concrete salt thus obtained to the 

 fire in order to destroy the acetic acid, and convert its bases 

 into carbonates. After which I extracted all the carbonate ot 

 potash from the ignited mass by pouring warm water upon it, and 

 saturated with sulphuric acid the alkaline liquor separated from 

 the part undissolved by water. This being afterwards dried, and 

 freed by ignition from the superfluous sulphuric acid, attorded 

 2-022 o-rm. of sulphate of potash, from which, during their solu- 

 tioninavery little water, U-0283 grm. of ignited sulphate ofhme 

 were separated ; so that the quantity of sulphate of potash 

 amounted to only 1-9985 grm. ... 



d. The powder left by the water c was dissolved in nitric acid, 

 and as the solution contained some barytes produced by the 

 decomposition of the acetate of barytes employed in too great 

 quantity for the purpose of precipitating the sulphuric acid, it 

 was mixed with a proper quantity of water, and sulphuric acid 

 dropped into it, until the sulphate of barytes ceased to be pre- 

 cipitated. This having been removed by filtration, I evaporated 

 the nitric solution to dryness, and adding more sulphuric acid, 

 converted the lime and magnesia into sulphates by the usual 

 method of evaporation and ignition ; these, when afterwards 

 separated by water, exhibited 0-580 grm. of anhydrous sulphate 

 of lime, and 1-475 grm. of anhydrous sulphate of magnesia. 



e. That portion of the mineral which was not soluble by boiling 

 <a) weighing 2-695 grms. I boiled for half an hour with double 

 that weight of carbonate of soda, in a proper quantity of water. 

 I then strained the liquor while it was yet hot, and caretully 

 washed the powder, left after filtration, in boihng water. Ihis 

 powder, when well dried, weighed 1-994 grm. By pourmg upon 

 it dilute nitric acid, it was almost entirely dissolved, with etter- 

 vescence, and there remained only red oxide of iron, weighing 

 not more than 0-020 grm. . . 



/. The nitric solution of the powder on being mixed witli 

 caustic ammonia deposited 0-005 grm. more of hydrate of oxide ot 



