Description of an Acid Principle, &c. 25 
jine precipitate of deutoxide of barium is thrown down, of the 
form of pearly scales, but little soluble in water; but at the tem- 
perature of 50° this liquor decomposes it, and converts it into 
oxygen gas and barytes, or protoxide of barium. 
Like barytes, both strontian and lime are capable of being su- 
peroxygenized by the superoxygenized acids. The hydrate of 
deutoxide of strortian has a considerable resemblance to that of 
barium; while that of lime is in finer plates. 
It seems probable that I shall be able, by the same methods 
to oxygenize the earths, or some of them; and to superoxidize 
many of the metallic oxides. To effect this, I propose to put an 
excess of base with the acid, or to dissolve the base in the acid 
and then to precipitate by potash: or I will put the oxygenized 
‘muriates in contact with oxide of silver, which, by seizing the 
muriatic acid, will favour the combination of the oxygen with the 
oxide wished to be superoxygenized. 
VII. Description of an Acid Principle prepared from the Lithic 
or Uric Acid. By Wiut1amM Prout, M.D. Communicated 
by W. H. Wottaston, M.D. F.R.S.* 
Durise an investigation of the principles of the urine, with the 
view of elucidating the pathology of that secretion, I was led to 
examine the well-known beautiful purple substance produced by 
the action of the nitric acid and heat upon the lithic acid, and 
which has usually been considered as one of the characteristic 
distinctions of the lithic acid. This purple substance proved to 
be a compound of ammonia, and a peculiar principle having the 
properties of an acid ;—the description of which, and of its com- 
pounds, constitutes the object of the present paper. 
This acid principle may be obtained by. digesting pure lithic 
acid in dilute nitric acid: an effervescence takes place, and the 
lithic acid is dissolved.. The excess of nitric acid is then to be 
neutralized with ammonia, and the whole slowly concentrated by 
evaporation. As the evaporation proceeds, the colour of the so- 
lution gradually becomes of a deeper purple, and dark red granu- 
lar crystals (sometimes of a greenish hue externally) soon begin 
to separate in abundance. These crystals are a compound of am- 
monia with the acid principle in question. The ammonia may 
be removed by the sulphuric or muriatic acid, and thus the acid 
principle obtained in a separate state. As, however, I found 
some little care requisite to obtain the acid quite free from co- 
lour, it may not be deemed superfluous to state the precise me- 
thod I usually followed for that purpose. ‘The compound with 
* From the Transactions of the Royal Society for 1818, Part IT. 
ammonia, 
