78 
The philosopher of the last century even went so far as to declare this 
common principle to be the u nitro-aerial particles (the oxygen of mo¬ 
dern times) which unite with different bases, and thus constitute the several 
acids* 
In his fourth chapter, “ on the origin of acids,” we see him combating 
the received opinion, “ denying that the vitriolic acid is contained in Sul¬ 
phur before deflagration.” 
He attributes “ its change to the affinity its base has for the nitro-aerial 
particles, which convert the sulphur into sharp sword-like atoms, giving 
them the poignancy which constitutes the character of an acid.” 
“ If vitriol,” says he, “ be calcined till the acid be totally expelled, and 
then exposed to the air, it will be anew impregnated with an acid, by the 
slow combination of the nitro-aerial particles with the sulphur; for it is 
impossible to conceive in what other way the spirit of vitriol can be re¬ 
generated*” 
“ The rust of iron also is produced by the nitro-aerial particles attack¬ 
ing the iron; and the effect of exposure to air is only a slower process, as 
if the iron were moistened by some acid.” 
How consonant are these ideas with the doctrines of modern chemis¬ 
try! 
The unfortunate Lavoisier in a series of Essays* taught his ungrateful 
countrymen “ the composition of the vitriolic, phosphoric, and nitrous acids.” 
“ Many additional experiments,” says this Philosopher in Essay VIII. 
have enabled me to generalise this doctrine, and to pronounce that this pure 
and highly respirable air is the constitutive principle of acidity; that this 
principle is common to all acids; and that the difference by which they are 
distinguished from each other is produced by the union of one or more prin¬ 
ciples, besides this air , so as to constitute the particular form under which 
each acid appears.” 
Having piemised thus much respecting the nature and composition of 
acids, we come now to the consideration of the important experiments of 
Humboldt, which were made in the year 1793. 
* Vl ^f ^ ss y s > or Memoirs, read before the Royal Academy of Sciences, translated by Thomas 
Henry, I. R. S. J 
