on various Objects, 4 1 5 



till a white fume began to rise from it, but it did not lose 

 the Vo- o^ ^ grain in weight. After the muriate of potash 

 had been washed out ot ihe tray, and it had been cleaned 

 and dried, it was found to have lost about a third of a 

 grain, which was platina in a metallic state, and that had 

 alloyed with the potassium where it was in contact with 

 the tray, during the combustion. There was no appearance 

 of any water being separated in the process. A little mu- 

 riate of potash sublimed ; this was washed out of the re^ 

 tort, and obtained by evaporation : it did not equal l of 

 a grain. 



Now if the data for calculation be taken from this last 

 experiment, 8 grains of potassium will combine with 1*4 

 grains of oxygen, to form 9*4 grains of potash, and 6-6 — 

 1*4 = 5*2, the quantity of muriatic acid combined with the 

 potash, which would give in the 100 parts in muriate of 

 potash, 33*6 of acid, and 64-4 of potash; but 35*6 of 

 murialic acid, according to M. Berthollet's estimation, 

 would demand 71*1 of alkali, in the state of dryness in 

 which it exists in muriate of potash, and 71*1-— 64*4 =: 

 fi*7— so thatthe potash taken as a standard by M. Ber- 

 thollet, contains at least 9 per cent, more water ' than th.at 

 existing in the p©tash formed by the combustion of potas- 

 sium in muriatic acid gas, which consequently may with 

 much more propriety be regarded as the dry alkali*.' 



After these illustrations, I trust the fonncr opinions 

 which I ventured to bring forward, concerning the me- 

 tals of the fixed alkalies, will be considered as accurate, 

 and that potassium and sodium can with no more pro- 

 priety be considered as compounds, than any of the 

 common metallic sulstances; and that potash and soda, 

 as formed by the combustion of the metals, are pure me- 

 tallic oxides, in which no water is known to exist. 



Thess conclusions must be considered as entirely inde^ 

 pendent of hypothetical opinions, concerning the existence 

 of hydrogen in combustible bodies, as a common principle 

 of inflanmiability, and of intimately cotnh'ned water, as an 

 essential constituent of acids, alkalies, and oxides : this part 

 of the inquiry I shall reserve for the conclusion of the 

 lecture, and I shall first consider the nature of the metal of 

 ammonia, and the metals of the earths. 



[To be continued.] 



* Consequently M. Berthollet's fused potash must contain nearly 23 per 

 cent, of water. From my own observations I am inclined to believe, that 

 potash kept for some time in a red heat contains J6 or 17 percent, of wa- 

 ter, taking the potash formed by the combustion of potassium as the dry 

 standard. 



LXIf. Oh^ 



