Page:Proceedings of the Royal Society of London Vol 1.djvu/371

Rh have misled the French chemists, and with the most scrupulous attention 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 uniting with the tellurium, forms a hydro-telluret of potash, which communicates its purple colour to the water.

When a fusible alloy of potasium 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 indication of the presence of moisture.

But in order to compare potassium with its corresponding quantity