ON THE ALKALINE METAlLOinS. 3(55 



Another circumstance is to be attended to, of much im- The calculatioit 

 portance with regard to the conclusion, so far as it relates by the water ia 

 to the general theory. The estimate of 14 per cent of potash not be 

 water in ignited potash is the lowest that has been made, determitlcdr 

 Berthollet himself, on whose authority it rests, has consi- 

 dered it probable, that there is a larger quantity ; the ab- 

 straction of the whole, even by its decomposition, being 

 prevented by the powerful affinity exerted to the last por- 

 tions. By d'Arcet the proportion has been stated at 27 

 in 100 parts. Mr. Davy has inferred from an experiment, 

 in which potassium was converted into muriate of potash in 

 Aiuriatic acid gas, that fused potash must contain nearly 23 

 per cent of water ; and more lately he has remarked, that, 

 if the proportion were to be judged of from the loss of 

 weight in combining common potash with boracic acid, it 

 would appear to be from 19 to 20 per cent. If we take the 

 lowest of these numbers, 20, then the five grains of ignited 

 potash, containing 20 per cent, neutralizing 139 grains, 5 

 grains of real potash ought to neutralize 174, and this is the 

 quantity that ought to have been neutralized hy 4*3 of 

 potassium, supposing it to form the real alkali by oxi- 

 gen a ti on. 



The result, therefore, from this mode of experiment can, The result, 



not be considered as invalidating the result from the more j-iiable with 

 tfitectmode of trying the alkaline strength of the actual pro- the hypothesis. 

 duct of the combustion of potassium, and even by itself is 

 not incbnipatible with the conclusion, that a portion of hi- 

 drogen exists in potassium, but rather serves to establish it. 



The circumstance, that there is no sensible evolution of Argument from 

 hidrogen in the decomposition of common potash by galva- jj^j^Qgej^ 

 nisni, still appears to me to go far towards establishing the 

 opinion, that hidrogen enters into thecomposi-tion of pot£ts« 

 »ium. Mr. Davy, in reply to Mr. Dalton, who had stated 

 this in support of the opinion of Gay-Lussac and Thenard, 

 has lately remarked, that, in using a weak galvanic pawer^ 

 such as that which he employed in his first experiments, and 

 by which small quantities only of the metals are procured, 

 there is no sensible effervescence; but that, when from 500 

 to 1000 plates are used, there is a violent effervescence, and opposed by iti 

 a production of hidrogen, and sometimes of potassurettecir^^l^'°^""*^®' 



* • 7 . r ^ certain circun- 



'"" ' birogeOp itances. 



