38 REPORT—1846, 
fering from niobium, and to this metal he has given the name of Pelopium, from 
Pelops the son of Tantalus and the brother of Niobe. The tantalite of Bavaria is 
therefore now shown to contain three metals—tantalium, niobium and pelopium. 
These differ from each other in specific gravity, and they exhibit different and pecu- 
liar chemical properties. 
On Cavendish’s Experiment respecting the production of Nitric Acid. 
By Prof. Dauseny, M.D., F.RS. 
Dr. Daubeny stated the result of some experiments he had instituted with the 
view of ascertaining whether the production of nitric acid by electricity, as was first 
effected by Cavendish, really arose from the direct union of oxygen with nitrogen, or 
was produced indirectly through the presence of minute portions of ammonia. For 
this purpose he deprived the air, through which the electrical sparks were to be 
passed, of water, and of any traces of ammonia that might have been contained in it, 
by allowing it to stand in contact with concentrated sulphuric acid for some time 
previous to the commencement of the experiment. Even in this case, although the 
air had been in contact with no liquid except the mercury over which it was con- 
fined, the usual diminution of volume took place after the electrical sparks had been 
passed through it, and solution of litmus, when introduced into the tube, became 
sensibly reddened. Hence the author infers that nitrogen does combine directly 
with oxygen, as it is now known to do with carbon, but he still questions whether 
it can do so with gaseous hydrogen, since ammonia cannot be formed, as nitric acid 
is, by means of electricity ; and, as in all the cases in which ammonia has been pro- 
duced artificially, one of the elements appears to have existed in what is called a 
nascent state. But if nitrogen can be made to combine directly with oxygen, how 
comes it that through the operation of thunder-storms the composition of the whole 
atmosphere has not before this time been changed by the production in it of con- 
siderable quantities of nitric acid? This the author explains by the small amount of 
heat generated by the union of the two gases, owing to which only those particles 
combine which lie contiguous to the line of the electrical spark ; whereas in other 
cases, as in that of the union of oxygen with hydrogen, so much heat is elicited 
by the union of those particles which are affected by the passage of the electrical 
spark, that a condensation of other portions of the mixture results, whence will arise 
a union of more of the particles, and an extrication of a larger amount of heat. In 
this way the explosion propagates itself through all parts of the mixture with a ra- 
pidity which causes it to be considered by us as instantaneous. In all cases however 
in which gaseous elements that can remain together without acting upon each other 
are made to unite, the modus operandi, whether it be by electricity, by heat, or (as in 
the case of porous bodies) by adhesive affinity, appears to be the same, that is, such 
a condensation of the respective gases as shall bring their particles within the sphere 
of their mutual affinity. 
On the extent to which Fluoride of Calcium is soluble in Water at 60° F. 
By Grorce Witson, M.D. 
In April of this year, 1846, Dr. Wilson read a paper to the Royal Society of 
Edinburgh announcing the solubility of fluoride of calcium in water, and stating 
that in consequence of observing this fact, he had been led to seek for that salt in 
milk, in blood, and in sea-water, where it had not been previously detected, but in 
all of which he found it. He also mentioned that he was able to confirm the re- 
sults of previous observers as to the presence of fluoride of calcium in natural waters, 
in plants and in animal remains, as well as in the urine of man. 
Since that paper was read, Dr. Wilson ascertained the extent to which fluoride of 
calcium is soluble in water at 60° F. ; and as it is a point of some interest in connexion 
with geological and mineralogical, as well as with chemical speculations, he brought 
it before the Chemical Section of the Association. The experiments recorded below 
were performed with a solution of native well-crystallized fluor spar, prepared by 
boiling distilled water upon the powdered fluor, which had been previously purified 
by digestion with warm aqua regia, so as to remove any trace of metallic oxides, 
lime-salts or the like, which might be present. The solution at 212° F., was filtered 
