351 



have misled the French chemists, and with the most scrupulous at- 

 tention to the products. 



When the experiment is conducted in tubes of iron, there is always 

 a conversion of a portion of potassium into potash, a loss of nitrogen, 

 and a production of hydrogen ; but when platina or copper tubes are 

 employed, the quantity of potassium remains the same, there is no 

 loss of nitrogen, but there is a loss greater or less of hydrogen. The 

 explanation suggested for this difference is, that an affinity of these 

 metals for potassium may prevent its attracting oxygen from the 

 ammonia. 



For the decomposition of ammonia, sodium seems preferable to 

 potassium, on account of the greater facility of employing it free from 

 moisture ; as the latter oxidates more rapidly at the surface, while 

 transferring from one vessel to another, and more rapidly attracts 

 moisture when oxidated. 



Mr. Ritter founds the same opinion, that hydrogen is a constituent 

 part of potassium and sodium, upon a singular circumstance that he 

 has observed respecting tellurium ; for he finds that this is the only 

 metal by which potassium cannot be procured, when it is used as the 

 conductor of voltaic electricity ; and he ascribes the difference to the 

 affinity of tellurium for hydrogen being stronger than that of potash. 



From many experiments which Mr. Davy has made upon tellurium, 

 and upon its alloys with potassium, he finds that tellurium unites 

 with hydrogen as a solid hydruret of tellurium ; that it unites with 

 a larger proportion of hydrogen as telluretted hydrogen, (a gas very 

 analogous to sulphuretted hydrogen) ; that this gas combines with 

 potash, forming a compound, corresponding to hydro -sulphuret of 

 potash, and communicating to water a deep purple or claret colour. 



After having thus ascertained the properties of tellurium, he found 

 that when potash is acted upon by a very powerful battery, by means 

 of a surface of tellurium at the negative pole, an alloy of tellurium 

 and potassium is formed, which has the colour of nickel ; when this 

 alloy is thrown into water, the hydrogen, which in other instances is 

 given off with effervescence, is not, in this case, extricated, but uni- 

 ting with the tellurium, forms a hydro-telluret of potash, which com- 

 municates its purple colour to the water. 



When a fusible alloy of potassium and tellurium was heated in 

 ammoniacal gas, the permanent elastic fluid generated was nitrogen, 

 not hydrogen, as is the case when potassium is employed alone; and 

 this is considered by Mr. Davy as a proof, that in each instance the 

 gas is derived from the ammonia and not from the metal, as the 

 French chemists have supposed. 



If the metals of potash and soda contained hydrogen, then water 

 should be formed when they are burned. But when potassium is 

 burned in close vessels in dry oxygen gas, or when sodium has been 

 burned even in the open air, they do not yield hydrogen by being 

 heated with filings of iron or of zinc, and they give no other indica- 

 tion of the presence of moisture. 



But in order to compare potassium with its corresponding quantity 



