some observations respecting the different quantities of uric acid
voided by birds living upon different kinds of food, not being produced by those that live entirely upon fish.
The tendency of the author in the present investigation, is to re- turn to the opinion respecting the relation of muriatic acid and oxy- muriatic acids to each other, which was originally entertained by Scheele.
According to that most illustrious chemist, the oxymuriatic was the more simple body, and by union with phlog'iston became muriatic acid. But from many experiments made soon after by Berthollet, it was inferred that the latter was simple, and by union with oxygen became converted into oxymuriatic acid. In Mr. Davy's former at- tempts to obtain the base of muriatic acid by potassium, he has not been able to separate anything from it but hydrogen. In Dr. Henry's endeavours by electricity to decompose the muriatic acid, hydrogen and oxymuriatic acid were evolved; and conversely, Mr. Davyhas in no instance been able to separate oxygen from oxymuriatic acid, or even to separate muriatic acid from dry muriates, without the assist- ance of hydrogen or water. He has hence been led to doubt the existence of oxygen in the substance called oxymuriatic acid, and has applied the most powerful means of abstracting oxygen from it without success; and indeed Messrs. Gay-Lussac and 'l‘henard, in their elaborate and interesting experiments, published in the Me- moires d’Arcueil, although they maintain that muriatic acid gas con- sists of muriatic acid and water, are not able to separate water from it, but only hydrogen; and themselves acknowledge that oxymuriatic acid, which they suppose to consist of muriatic acid and oxygen, am- not be decomposed by any known means.
The most extraordinary fact noticed by Mr. Davy is, that when charcoal is ignited to whiteness by the voltaic battery in oxymuriatic acid gas, no change whatever is produced, provided that the charcoal has been previously freed from moisture or from hydrogen by intense heat.
The vivid combustion of many bodies in this gas has favoured the presumption that it contained oxygen very loosely combined and ready to exert its utmost power of aflinity: but it is mere presumption; since heat and light result also from the intense agency of any other combination, without the presence of oxygen.
The resemblance of oxymuriatic acid combined with metals to other neutral salts, may be considered a strong argument in favour
- ↑ Communicated to the Royal Society a! the request of the Manager: of the Royal Institution.
