cfAllalies and 'Earths. 351 



attention to the difference of the phaenomena by pure fub- 

 llauces and thofe which are not fo; but \ (hall confine my- 

 felf to mention that exhibited by the experiment in queftion. 



When the pure charcoal is treated with potalh, as above 

 iliid ; and when an acid is added to the fohition feparated 

 ti-om the charcoal, in order to faturate the potafli, no other 

 pluvnomenon is obferved than a difencragement of carbonic 

 acid gas, which the potafli has abforbecl daring the courl'e of 

 operation. 



But, in Read of pure charcoal, if that which we firft em- 

 ployed be made ufe of, that is to fay, charcoal of white wood ; 

 by faturating the potafli employed, a very different rcfult will 

 be obtained. The acid, as foon as poured in, produces a dil- 

 engagement of carbonic acid. When a larger quantity ia 

 added, a great deal of fulphurated hydrogen gas is produced; 

 and by faturating the potaih a lari^e quantity of fulphur is 

 precipitated. This again explains the ftate in which the lime 

 is found, and perhaps the magneda, in the charcoal ; for there 

 is no need to fay tliat the fulphur obtained in this operation 

 mult arife from the i'ulphuric acid decompofed. There is no 

 doubt that the fu'phates of lime and magnefia contributed to 

 this circumftance, fince the quantities of thefe earths in the 

 charcoal were confiderable. This illU fcrves to explain the 

 obfervation made bv C. Deformes, who feveral times found 

 lime, magnefia, and alumine in the fame refiduum. By re- 

 collecting that thefe three earths exilt in charcoal, it wilh'be 

 readily feen whence they arofe. 



Ex(>. IX. By treating foda with charcoal in the fame man- 

 ner as the potaflt was treated, the above authors obtained 

 magnefia, alumine, and lime. It is here feen that this re- 

 fult is the fame as ougitt to be given by common charcoal. { 

 fliall therefore fay nothing further refpettiug this experiment, 

 than merely to announce that in treating pure foda witii 

 pure charcoal (that in particular arifing from the decompo- 

 fiiion of the carbonic acid), none of the above earths are ob- 

 tained. 



Exp. X. Muriate of potafli treated by charcoal gave to 

 Deformes lime. It is needlefs to obferve, in this tenth ex- 

 periment, that the lime arofe from the charcoal; fince, when 

 pure matters are employed, none of that fubltance is found. 



Exp. XI. The eleventh experiment, which, bcfides lime, 

 gave magnefia and alumine, will not give any of thele earths 

 when pure charcoal is employed. This experiment was made 

 with muriate of foda and charcoal. 



Kxp. XII. The twelfth experiment, which gave exaflly 

 the fame refults as the eleventh, was made by treating mu- 

 riate 



