Chemistry. XXIX. 
hydrogen. Indeed I conceive it to be merely carbonic oxide 
united to one third part of its volume of hydrogen gas. The 
name ought to indicate this, which I think is done by calling it 
hydro-carbonic oxide gas. 
4. Phosphorus.—Sir Humphry Davy’s experiments on the 
combustion of phosphorus, published in the Philosophical Trans- 
actions for 1818, and of which an account was given in the 
Annals of Philosophy, xiii. 210, exactly tally with my deductions 
from a set of experiments on phosphuretted hydrogen, and show 
in the most decisive manner, if any doubts were entertained on 
the subject, that the previous experiments of that gentleman on 
the combustion of phosphorus were inaccurate. I think it esta- 
blished by these experiments of Davy and by my own that the 
weight of an atom of phosphorus is 1°5, and that the composi- 
tion of the two acids of phosphorus is as follows: — 
, Phosphorus. Oxygen. 
Phosphorous acid. . .2)s,0:-200s 0+) 1°04 1 
PQ SOMOFIC AOI es inde ae.n pai ain as 15 +42 
But it must not be concealed that these numbers will not 
agree with the equivalent number for phosphoric acid as deduced 
from Berzelius’s analysis of the different phosphates. I think, 
therefore, that the subject still claims further investigation. 
5. Selenium.—In the historical sketch of the progress of 
chemistry during the year 1817, inserted in the Annals of Philo- 
sophy, xu. 1, will be found (p. 13) a short account of the proper- 
ties of this new substance. The kindness of Prof. Berzelius has 
put it in my power to examine this substance myself, and to make 
a few trials on its more prominent properties. And the full 
account of its properties has been given to the public by that 
skilful chemist in the fifth volume of the Afhandlingar; and a 
translation of his paper has been inserted in the ninth volume of 
the Annales de Chimie et Physique, from which I have extracted 
it for the sake of the readers of the Annals of Philosophy. From 
this paper, which will not have escaped the recollection of the 
reader, I shall select those circumstances of importance which 
were omitted last year. 
Berzelius made an ingenious set of experiments to determine 
the composition of selenic acid, and to deduce from this compo- 
sition the weight of an atom of selenium. He saturated a given 
weight of selenium with chlorine, and formed what he considered 
as a double acid; but which was obviously a chloride of selenium. 
When this chloride is treated with water, it is converted, as is’ 
the case with other chlorides, into selenic acid and muriatic acid. 
This is obviously occasioned by the decomposition of water, the 
hydrogen of which unites with the chlorine, and converts it into 
muriatic acid; while the oxygen unites to the selenium, and 
converts it into selenic acid. Hence if we know the weight of 
the selenium employed and of the muriatic acid produced, we 
