Analysis of the magnetical Pijrites. -2 1 3 



of potash, add an ounce of arsenic, it will not be saturated; 

 if you add two and a third, the case will be the same, and 

 so on : but till the point of this saturation be discovered, I 

 must repeat to them, your arsenical potash hitherto has 

 been nothing but potash -f 1 + 2 + 3 of arsenic ; but as 

 I have not yet had tniie to verify M'hether the conihinatioti 

 will obey, as there is no reason to doubt, the law of rela- 

 tions, we must not be loo urgent to deduce from them con- 

 clusions. To conclude, these are results so variable, that 

 they annihilate your laws of proportion, and render your 

 apothegms illusory. Besides, Berthollet is too just not to 

 allow, that the series of the numbers by which t have en- 

 deavoured to represent the solutions of sulphuret of anti- 

 mony in its oxide, has^ not the least relation with uhat I 

 have hitherto called proportion in combinations. 



XXXVII. An Analysis of the magnetical Pyrites-, nitli 

 Remarks on some of the other Sidphurets of Iron. By 

 Charles Hatchett, Esq. F. R. S. 



[Concludtd f.om p. 1.1.7.] 



§ VIII. 



JC r»Q^f the whole which has been stated we find, 



1. That the substance called magnetical pyrites, which 

 has hitherto been found only in Saxony and a few other 

 places, is also a British mineral, and that, in Caernarvon- 

 shire, it forms a vein of considerable extent, breadth, and 

 depth. 



2. That the component ingredients of it are sulphur and 

 metallic iron ; the former bemg in the proportion of 36-50 

 or 37, and the latter about 63-50 or G3, 



3. That the chemical and other properties of this sub- 

 stance are very diU'erent front those of the common martial 

 pyrites, which, however, arc also composed of sulphur and 

 iron, varying in proportion, from 53-15 to 54-31 of sul- 

 pliur, and from 47-85 to 45-fi6 of metallic ir(m : the dif- 

 ference between the common jiyrites which were exauiined 

 being therefore 2-19, and the mean proportions amountiiKr 

 to 33-24 of sulphur, and 40-75 of inju ; consequently, the 

 tjinerence between the relative proportions, in the con'iposi- 

 tion of the magnetical pyrites and of the common pyrites, 

 js nearlv J6-74 or 16-24. 



4. Tliat, as the magnetical pyrites agrees in analytical 



O 3 results. 



