36 Mr. Davy’s Experiments on 
The second experiment was conducted with still more at- 
tention to minuteness. 3 grains of potassium were employed; 
above 22 cubical inches of muriatic acid gas were consumed ; 
the potassium burnt with the same brilliant phasnomena as in 
the last experiment, and the increase of weight of the tray 
was 6 ± grains. The muriate of potash was kept for some 
minutes in fusion in the tray, till a white fume began to rise 
from it, but it did not lose the 2 - r - of a grain in weight. After 
the muriate of potash had been washed out of the 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 muriate of 
potash sublimed ; this was washed out of the retort, and ob- 
tained by evaporation : it did not equal ~ of a grain. 
Now if the data for calculation be taken from this last ex- 
periment, 8 grains of potassium will combine with 3 .4 grains 
of oxygene, 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, 35.6 
of acid, and 64.4 of potash ; but 35.6 of muriatic acid accord- 
ing 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 = 6.7 — so that the potash taken as a 
standard by M. Berthollet, contains at least 9 per cent, more 
water, than that existing in the potash formed by the combus- 
tion of potassium in muriatic acid gas, which consequently may 
with much more propriety be regarded as the dry alkali.* 
* Consequently M. Behthollet’s fused potash must contain nearly 23 per cent. 
