132 On Sir B. Davys Theory of [Aug. 



by calculation, that while the oxygen of 100 of potash unites 

 with the hydrogen of 524748 of muriatic acid, the residual 

 potassium (861) combining with the chlorine (50 16) forms 

 136*26 of muriate of potash. But the materials employed were 

 in weight 1524748; so that a deficiency in the weight of the 

 product, of not less than 16*2 M8, remains to he accounted for. 

 It may, indeed, be said, that on account of the water contained 

 in potash, a deduction is requisite on either theory ; but as this 

 operates equally on both, while the other is entirely unnecessary 

 on the old theory, we are thus furnished with an apparently easy- 

 mode of discrimination. 



Nor does the analysis of the salt seem less decisive: according 

 to Sir H. Davy's theory, 100 parts of muriate of potash should 

 yield 35*976 °f muriatic acid, and 71*93 of anhydrous potash j 

 in all, 107-906. 



Moreover, in decomposing muriate of potash by nitrate of 

 silver, the potassium must be oxidated by decomposing either the 

 water or the oxide of silver. If by the former means, there 

 must be an evolution of 88*6 cubic inches of hydrogen from the 

 decomposition of 136*26 grs. of the salt. If in the latter way, 

 then, as 50*16 grs. of chlorine can decompose 239*2741 grs. of 

 oxide of silver, the oxygen of this quantity, which amounts to 

 nearly 22*085 grs., must unite with the potassium; but 81*6 grs. 

 of potassium can take 13*9 grs. of oxygen only : therefore there 

 must be an extrication of 8* 185 grs. of this gas, or about 

 24*0735 cubic inches. Beside, the residual muriate of silver 

 will not weigh 291*7 189 g rs -j 1)ut 267*3491 grs. only. 



Before concluding, I have only to remark, that the calcula- 

 tions above detailed are rendered in a great measure uncertain, 

 from the want of accurate and consistent statements of the 

 composition of potash, and of water, as well as of the quantity 

 of oxygen which may be obtained from a given portion of oxy- 

 muriatic gas. 



With regard to potash, the various statements given by 

 different chemists, and on different occasions, are full of per- 

 plexity. 



Sir H. Davy details two experiments, the mean result of 

 which was 13 9 per cent, of oxygen ;* and on the basis afforded 

 by this estimate, the calculations in the foregoing paper were 

 made : the method practised in these experiments was the com- 

 bustion of potassium in oxygen gas, the result of which process 

 is afterwards f said by Sir H. Davy to be peroxide of potassium. X 



* Phil. Trans. 1808, p. 28. + Phil. Tran>. 1811, p. 6. 



J Yet Ihe experiments detailed in page 4 of the Phil. Trans, for 1811 seem 

 to iii'licate that the peroxide of potassium coutains about 30 per cent, of 

 oxv^en; and MM. Gay-Lussac aud Thenard (Recherrhes, &c. i. p. 133) state 

 that it contain-, three times as much oxygen as exists in potash. 



