o/" Alkalies and Earths. 345 



made in the laboratory of the School of Mines, Is to inform 

 the public that I was afllRcd by the advice of C. Vauqueiin. 

 • I nuiii: rcqueft thole chcniills whofe opinions I auj about 

 to oppofe, to confider my labour as arifmg only from a defire 

 to difcover truth, and not as the refult of a vain preteiifion to 

 alter in anv manner the eftcem whicli they deferve, and the 

 gratitude due to them for their nimaerous and ufeful difco- 

 veries. I fliall therefore conlent myfelf with defcribing the 

 manner in which I repeated their experiments. I fliall ihow 

 the rel'ults of them, and I ihall leave to chemifts to deduce 

 from them fuch conclufions as they may think proper. 



Exp. I. The firft experiment, which confifts in the re- 

 duction of a metallic oxide by potafh, prefents nothing that 

 can fupport the obfervation or the above authors. The confe- 

 quence which they themfelves deduce from it is merely ac- 

 cefibry. Befides, it is known that feveral faline fubftances 

 deflttute of potalh pollefs this property. It' is known alfo, 

 that fire alone is fufficient to reduce the a\ide of lead era- 

 ployed in this operallun. 



. Ex-p. II. Guyton and Deformes decompofed in a platina 

 crucible fulphuret of potalh 3 and with the help of a ftrong 

 heat they obtained lime. 



I rejieaied this experiment with common fulphuret of pot- 

 afh; that is to fay, the i'ubltance commonly fold in the {hops 

 under the name of liver offulpbur', and having expofed it to 

 a ftrong heat, I obtained a refiduurn which, when treated 

 with water, was not entirely dilfolved. The inloluble part, 

 treated by nitric acid, was attacked; the nitric folution, iried 

 by the oxalate of anminnia, gave a great quantity of linie. 



vSufpecling that the lime found by this experiment might 

 arife from the potafli employed to make the fulphuret, I 

 made a fecond experiment with pure lulphuret of potadi, 

 prepared from potafli purified by alcohol and fublimated ful- 

 phur. I employed \G grammes of alkali and 8 of iulphur. 

 i he mixture, made in a mortar, and poured by portions into 

 a platina crucible (Irongly heated, left a matter of a rcddidi 

 brown colour, which, treated by water, was almofl: entirely 

 ditrolved. The finall rcfidiuim, which weighed only 4 centi- 

 grammes, being carefully examined, was found to be filcx 

 coloured by charcoal ; it arofe no doubt from the potafli, 

 which, as is well known, eafily diflblvis that earth. 



Exp. III. To perform this third experiment, they took 

 oxalate of potadi with fulphur. After the mixture was moift- 

 ened and pulverifed, it was treated with heal in a faud-bath, 

 fliid oxalate of lime was obtained. 



^s the above authors do not defcribe this experiment, and 



give 



